SERVER-32958 slaveOk,slaveOverrideOk replacement

declare read_preference dep. update service_entry_opint_embedded

169 files changed, 658 insertions, 660 deletions

diff --git a/src/mongo/client/embedded/SConscript b/src/mongo/client/embedded/SConscript
index 57f9fd9cc48..16d45f9fba5 100644
--- a/src/mongo/client/embedded/SConscript
+++ b/src/mongo/client/embedded/SConscript
@@ -16,6 +16,7 @@ env.Library(
     LIBDEPS_PRIVATE=[
         '$BUILD_DIR/mongo/db/auth/authcore',
         '$BUILD_DIR/mongo/db/auth/authmongod',
+        '$BUILD_DIR/mongo/db/command_can_run_here',
         '$BUILD_DIR/mongo/db/ops/write_ops_exec',
         '$BUILD_DIR/mongo/db/rw_concern_d',
         '$BUILD_DIR/mongo/db/s/sharding',
diff --git a/src/mongo/client/embedded/service_entry_point_embedded.cpp b/src/mongo/client/embedded/service_entry_point_embedded.cpp
index 003c5ff95d3..dedf60c54c5 100644
--- a/src/mongo/client/embedded/service_entry_point_embedded.cpp
+++ b/src/mongo/client/embedded/service_entry_point_embedded.cpp
@@ -36,6 +36,7 @@
 #include "mongo/db/auth/authorization_session.h"
 #include "mongo/db/auth/impersonation_session.h"
 #include "mongo/db/client.h"
+#include "mongo/db/command_can_run_here.h"
 #include "mongo/db/commands.h"
 #include "mongo/db/commands/fsync.h"
 #include "mongo/db/concurrency/global_lock_acquisition_tracker.h"
@@ -559,18 +560,13 @@ void execCommandDatabase(OperationContext* opCtx,
 
         if (!opCtx->getClient()->isInDirectClient() &&
             !MONGO_FAIL_POINT(skipCheckingForNotMasterInCommandDispatch)) {
-
-            bool commandCanRunOnSecondary = command->slaveOk();
-
-            bool commandIsOverriddenToRunOnSecondary =
-                command->slaveOverrideOk() && ReadPreferenceSetting::get(opCtx).canRunOnSecondary();
-
-            bool iAmStandalone = !opCtx->writesAreReplicated();
-            bool canRunHere = iAmPrimary || commandCanRunOnSecondary ||
-                commandIsOverriddenToRunOnSecondary || iAmStandalone;
-
-            // This logic is clearer if we don't have to invert it.
-            if (!canRunHere && command->slaveOverrideOk()) {
+            auto allowed = command->secondaryAllowed();
+            bool alwaysAllowed = allowed == Command::AllowedOnSecondary::kAlways;
+            bool couldHaveOptedIn = allowed == Command::AllowedOnSecondary::kOptIn;
+            bool optedIn =
+                couldHaveOptedIn && ReadPreferenceSetting::get(opCtx).canRunOnSecondary();
+            bool canRunHere = commandCanRunHere(opCtx, dbname, command);
+            if (!canRunHere && couldHaveOptedIn) {
                 uasserted(ErrorCodes::NotMasterNoSlaveOk, "not master and slaveOk=false");
             }
 
@@ -594,7 +590,7 @@ void execCommandDatabase(OperationContext* opCtx,
                 // Check ticket SERVER-21432, slaveOk commands are allowed in drain mode
                 uassert(ErrorCodes::NotMasterOrSecondary,
                         "node is in drain mode",
-                        commandIsOverriddenToRunOnSecondary || commandCanRunOnSecondary);
+                        optedIn || alwaysAllowed);
             }
         }
 
diff --git a/src/mongo/db/SConscript b/src/mongo/db/SConscript
index 6e9ac5f0aaa..3869a22a464 100644
--- a/src/mongo/db/SConscript
+++ b/src/mongo/db/SConscript
@@ -513,11 +513,26 @@ env.Library(
         'auth/authcore',
         'commands/server_status_core',
         'commands/test_commands_enabled',
+        'command_can_run_here',
         'service_context',
         '$BUILD_DIR/mongo/db/catalog/uuid_catalog',
     ],
 )
 
+env.Library(
+    target='command_can_run_here',
+    source=[
+        'command_can_run_here.cpp',
+    ],
+    LIBDEPS=[
+        '$BUILD_DIR/mongo/base',
+        '$BUILD_DIR/mongo/client/read_preference',
+        '$BUILD_DIR/mongo/db/repl/repl_coordinator_interface',
+        'service_context',
+    ],
+)
+
+
 env.CppUnitTest(
     target="commands_test",
     source=[
@@ -597,6 +612,7 @@ env.Library(
         '$BUILD_DIR/mongo/base',
         '$BUILD_DIR/mongo/transport/service_entry_point',
         'auth/authmongod',
+        'command_can_run_here',
         'commands/dcommands_fsync',
         'concurrency/lock_manager',
         'curop',
diff --git a/src/mongo/db/auth/sasl_commands.cpp b/src/mongo/db/auth/sasl_commands.cpp
index 433439ad2b8..8a67b45879d 100644
--- a/src/mongo/db/auth/sasl_commands.cpp
+++ b/src/mongo/db/auth/sasl_commands.cpp
@@ -81,8 +81,8 @@ public:
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
         return false;
     }
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
     bool requiresAuth() const override {
         return false;
@@ -107,8 +107,8 @@ public:
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
         return false;
     }
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
     bool requiresAuth() const override {
         return false;
diff --git a/src/mongo/db/command_can_run_here.cpp b/src/mongo/db/command_can_run_here.cpp
new file mode 100644
index 00000000000..c945380cc3e
--- /dev/null
+++ b/src/mongo/db/command_can_run_here.cpp
@@ -0,0 +1,57 @@
+/**
+ *    Copyright (C) 2018 MongoDB Inc.
+ *
+ *    This program is free software: you can redistribute it and/or  modify
+ *    it under the terms of the GNU Affero General Public License, version 3,
+ *    as published by the Free Software Foundation.
+ *
+ *    This program is distributed in the hope that it will be useful,
+ *    but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *    GNU Affero General Public License for more details.
+ *
+ *    You should have received a copy of the GNU Affero General Public License
+ *    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ *    As a special exception, the copyright holders give permission to link the
+ *    code of portions of this program with the OpenSSL library under certain
+ *    conditions as described in each individual source file and distribute
+ *    linked combinations including the program with the OpenSSL library. You
+ *    must comply with the GNU Affero General Public License in all respects for
+ *    all of the code used other than as permitted herein. If you modify file(s)
+ *    with this exception, you may extend this exception to your version of the
+ *    file(s), but you are not obligated to do so. If you do not wish to do so,
+ *    delete this exception statement from your version. If you delete this
+ *    exception statement from all source files in the program, then also delete
+ *    it in the license file.
+ */
+
+#include "mongo/platform/basic.h"
+
+#include "mongo/db/command_can_run_here.h"
+
+#include "mongo/db/repl/replication_coordinator.h"
+#include "mongo/client/read_preference.h"
+#include "mongo/util/assert_util.h"
+
+namespace mongo {
+
+bool commandCanRunHere(OperationContext* opCtx, const std::string& dbname, const Command* command) {
+    auto replCoord = repl::ReplicationCoordinator::get(opCtx);
+    if (replCoord->canAcceptWritesForDatabase_UNSAFE(opCtx, dbname))
+        return true;  // primary: always ok
+    if (!opCtx->writesAreReplicated())
+        return true;  // standalone: always ok
+    switch (command->secondaryAllowed()) {
+        case Command::AllowedOnSecondary::kAlways:
+            return true;
+        case Command::AllowedOnSecondary::kNever:
+            return false;
+        case Command::AllowedOnSecondary::kOptIn:
+            // Did the user opt in?
+            return ReadPreferenceSetting::get(opCtx).canRunOnSecondary();
+    }
+    MONGO_UNREACHABLE;
+}
+
+}  // namespace mongo
diff --git a/src/mongo/db/command_can_run_here.h b/src/mongo/db/command_can_run_here.h
new file mode 100644
index 00000000000..18ac4653593
--- /dev/null
+++ b/src/mongo/db/command_can_run_here.h
@@ -0,0 +1,40 @@
+/**
+ *    Copyright (C) 2018 MongoDB Inc.
+ *
+ *    This program is free software: you can redistribute it and/or  modify
+ *    it under the terms of the GNU Affero General Public License, version 3,
+ *    as published by the Free Software Foundation.
+ *
+ *    This program is distributed in the hope that it will be useful,
+ *    but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *    GNU Affero General Public License for more details.
+ *
+ *    You should have received a copy of the GNU Affero General Public License
+ *    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ *    As a special exception, the copyright holders give permission to link the
+ *    code of portions of this program with the OpenSSL library under certain
+ *    conditions as described in each individual source file and distribute
+ *    linked combinations including the program with the OpenSSL library. You
+ *    must comply with the GNU Affero General Public License in all respects for
+ *    all of the code used other than as permitted herein. If you modify file(s)
+ *    with this exception, you may extend this exception to your version of the
+ *    file(s), but you are not obligated to do so. If you do not wish to do so,
+ *    delete this exception statement from your version. If you delete this
+ *    exception statement from all source files in the program, then also delete
+ *    it in the license file.
+ */
+
+#pragma once
+
+#include <string>
+
+#include "mongo/db/commands.h"
+#include "mongo/db/operation_context.h"
+
+namespace mongo {
+
+bool commandCanRunHere(OperationContext* opCtx, const std::string& dbname, const Command* command);
+
+}  // namespace mongo
diff --git a/src/mongo/db/commands.h b/src/mongo/db/commands.h
index f1e580b69f8..58cadbfb3ef 100644
--- a/src/mongo/db/commands.h
+++ b/src/mongo/db/commands.h
@@ -188,6 +188,7 @@ struct CommandHelpers {
 class Command {
 public:
     using CommandMap = StringMap<Command*>;
+    enum class AllowedOnSecondary { kAlways, kNever, kOptIn };
 
     /**
      * Constructs a new command and causes it to be registered with the global commands list. It is
@@ -262,17 +263,7 @@ public:
         return false;
     }
 
-    /* Return true if slaves are allowed to execute the command
-    */
-    virtual bool slaveOk() const = 0;
-
-    /**
-     * Return true if the client force a command to be run on a slave by
-     * turning on the 'slaveOk' option in the command query.
-     */
-    virtual bool slaveOverrideOk() const {
-        return false;
-    }
+    virtual AllowedOnSecondary secondaryAllowed() const = 0;
 
     /**
      * Override and return fales if the command opcounters should not be incremented on
diff --git a/src/mongo/db/commands/SConscript b/src/mongo/db/commands/SConscript
index 36107dce430..378e475dc44 100644
--- a/src/mongo/db/commands/SConscript
+++ b/src/mongo/db/commands/SConscript
@@ -212,6 +212,7 @@ env.Library(
         '$BUILD_DIR/mongo/db/catalog/collection',
         '$BUILD_DIR/mongo/db/catalog/index_key_validate',
         '$BUILD_DIR/mongo/db/cloner',
+        '$BUILD_DIR/mongo/db/command_can_run_here',
         '$BUILD_DIR/mongo/db/commands',
         '$BUILD_DIR/mongo/db/exec/stagedebug_cmd',
         '$BUILD_DIR/mongo/db/index/index_access_method',
diff --git a/src/mongo/db/commands/apply_ops_cmd.cpp b/src/mongo/db/commands/apply_ops_cmd.cpp
index f2b41250973..d0bce7a629e 100644
--- a/src/mongo/db/commands/apply_ops_cmd.cpp
+++ b/src/mongo/db/commands/apply_ops_cmd.cpp
@@ -202,8 +202,8 @@ class ApplyOpsCmd : public BasicCommand {
 public:
     ApplyOpsCmd() : BasicCommand("applyOps") {}
 
-    bool slaveOk() const override {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
     bool supportsWriteConcern(const BSONObj& cmd) const override {
diff --git a/src/mongo/db/commands/authentication_commands.cpp b/src/mongo/db/commands/authentication_commands.cpp
index 58e34b87f9d..0b925c3d84c 100644
--- a/src/mongo/db/commands/authentication_commands.cpp
+++ b/src/mongo/db/commands/authentication_commands.cpp
@@ -97,8 +97,8 @@ class CmdGetNonce : public BasicCommand {
 public:
     CmdGetNonce() : BasicCommand("getnonce"), _random(SecureRandom::create()) {}
 
-    bool slaveOk() const final {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
 
     std::string help() const final {
@@ -259,8 +259,8 @@ CmdAuthenticate cmdAuthenticate;
 
 class CmdLogout : public BasicCommand {
 public:
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
     virtual void addRequiredPrivileges(const std::string& dbname,
                                        const BSONObj& cmdObj,
diff --git a/src/mongo/db/commands/authentication_commands.h b/src/mongo/db/commands/authentication_commands.h
index a5123fb932b..5e886827256 100644
--- a/src/mongo/db/commands/authentication_commands.h
+++ b/src/mongo/db/commands/authentication_commands.h
@@ -40,8 +40,8 @@ class CmdAuthenticate : public BasicCommand {
 public:
     static void disableAuthMechanism(std::string authMechanism);
 
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
     std::string help() const override {
         return "internal";
diff --git a/src/mongo/db/commands/clone.cpp b/src/mongo/db/commands/clone.cpp
index e7ec4973221..0e50419a5df 100644
--- a/src/mongo/db/commands/clone.cpp
+++ b/src/mongo/db/commands/clone.cpp
@@ -56,11 +56,10 @@ class CmdClone : public BasicCommand {
 public:
     CmdClone() : BasicCommand("clone") {}
 
-    virtual bool slaveOk() const {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
-
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
         return true;
     }
diff --git a/src/mongo/db/commands/clone_collection.cpp b/src/mongo/db/commands/clone_collection.cpp
index 0a8ddde8bea..493ea75d044 100644
--- a/src/mongo/db/commands/clone_collection.cpp
+++ b/src/mongo/db/commands/clone_collection.cpp
@@ -63,11 +63,10 @@ class CmdCloneCollection : public ErrmsgCommandDeprecated {
 public:
     CmdCloneCollection() : ErrmsgCommandDeprecated("cloneCollection") {}
 
-    virtual bool slaveOk() const {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
-
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
         return true;
     }
diff --git a/src/mongo/db/commands/collection_to_capped.cpp b/src/mongo/db/commands/collection_to_capped.cpp
index 14a3bf3f00e..56dad067123 100644
--- a/src/mongo/db/commands/collection_to_capped.cpp
+++ b/src/mongo/db/commands/collection_to_capped.cpp
@@ -52,8 +52,8 @@ using std::stringstream;
 class CmdCloneCollectionAsCapped : public ErrmsgCommandDeprecated {
 public:
     CmdCloneCollectionAsCapped() : ErrmsgCommandDeprecated("cloneCollectionAsCapped") {}
-    virtual bool slaveOk() const {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
         return true;
@@ -151,8 +151,8 @@ public:
 class CmdConvertToCapped : public ErrmsgCommandDeprecated {
 public:
     CmdConvertToCapped() : ErrmsgCommandDeprecated("convertToCapped") {}
-    virtual bool slaveOk() const {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
         return true;
diff --git a/src/mongo/db/commands/compact.cpp b/src/mongo/db/commands/compact.cpp
index e914d2f606d..4a52700118c 100644
--- a/src/mongo/db/commands/compact.cpp
+++ b/src/mongo/db/commands/compact.cpp
@@ -61,8 +61,8 @@ public:
     virtual bool adminOnly() const {
         return false;
     }
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
     virtual bool maintenanceMode() const {
         return true;
diff --git a/src/mongo/db/commands/conn_pool_stats.cpp b/src/mongo/db/commands/conn_pool_stats.cpp
index 298bbda74d4..e799257d923 100644
--- a/src/mongo/db/commands/conn_pool_stats.cpp
+++ b/src/mongo/db/commands/conn_pool_stats.cpp
@@ -53,8 +53,8 @@ public:
         return "stats about connections between servers in a replica set or sharded cluster.";
     }
 
-    bool slaveOk() const override {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
 
     bool supportsWriteConcern(const BSONObj& cmd) const override {
diff --git a/src/mongo/db/commands/conn_pool_sync.cpp b/src/mongo/db/commands/conn_pool_sync.cpp
index 44893d621e6..ecf135bb7e6 100644
--- a/src/mongo/db/commands/conn_pool_sync.cpp
+++ b/src/mongo/db/commands/conn_pool_sync.cpp
@@ -62,8 +62,8 @@ public:
         globalConnPool.flush();
         return true;
     }
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
 
 } poolFlushCmd;
diff --git a/src/mongo/db/commands/connection_status.cpp b/src/mongo/db/commands/connection_status.cpp
index 14e6413014f..80b4fdd9e2c 100644
--- a/src/mongo/db/commands/connection_status.cpp
+++ b/src/mongo/db/commands/connection_status.cpp
@@ -41,8 +41,8 @@ using std::stringstream;
 class CmdConnectionStatus : public BasicCommand {
 public:
     CmdConnectionStatus() : BasicCommand("connectionStatus") {}
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
         return false;
diff --git a/src/mongo/db/commands/copydb.cpp b/src/mongo/db/commands/copydb.cpp
index 297ec8f1c10..99178166050 100644
--- a/src/mongo/db/commands/copydb.cpp
+++ b/src/mongo/db/commands/copydb.cpp
@@ -95,8 +95,8 @@ public:
         return true;
     }
 
-    virtual bool slaveOk() const {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
diff --git a/src/mongo/db/commands/copydb_start_commands.cpp b/src/mongo/db/commands/copydb_start_commands.cpp
index 59c21a4fcd2..6f675971ea0 100644
--- a/src/mongo/db/commands/copydb_start_commands.cpp
+++ b/src/mongo/db/commands/copydb_start_commands.cpp
@@ -78,11 +78,10 @@ public:
         return true;
     }
 
-    virtual bool slaveOk() const {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
-
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
         return false;
     }
diff --git a/src/mongo/db/commands/count_cmd.cpp b/src/mongo/db/commands/count_cmd.cpp
index 639d842e1db..129af8c89de 100644
--- a/src/mongo/db/commands/count_cmd.cpp
+++ b/src/mongo/db/commands/count_cmd.cpp
@@ -63,13 +63,12 @@ public:
         return false;
     }
 
-    virtual bool slaveOk() const {
-        // ok on --slave setups
-        return repl::getGlobalReplicationCoordinator()->getSettings().isSlave();
-    }
-
-    virtual bool slaveOverrideOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        if (repl::getGlobalReplicationCoordinator()->getSettings().isSlave()) {
+            // ok on --slave setups
+            return Command::AllowedOnSecondary::kAlways;
+        }
+        return Command::AllowedOnSecondary::kOptIn;
     }
 
     virtual bool maintenanceOk() const {
diff --git a/src/mongo/db/commands/cpuload.cpp b/src/mongo/db/commands/cpuload.cpp
index be297b83ed6..587ee0af693 100644
--- a/src/mongo/db/commands/cpuload.cpp
+++ b/src/mongo/db/commands/cpuload.cpp
@@ -42,8 +42,8 @@ using std::stringstream;
 class CPULoadCommand : public BasicCommand {
 public:
     CPULoadCommand() : BasicCommand("cpuload") {}
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
     virtual bool isWriteCommandForConfigServer() const {
         return false;
diff --git a/src/mongo/db/commands/cpuprofile.cpp b/src/mongo/db/commands/cpuprofile.cpp
index 51cc7d8a205..396e396856d 100644
--- a/src/mongo/db/commands/cpuprofile.cpp
+++ b/src/mongo/db/commands/cpuprofile.cpp
@@ -71,8 +71,8 @@ namespace {
 class CpuProfilerCommand : public ErrmsgCommandDeprecated {
 public:
     CpuProfilerCommand(char const* name) : ErrmsgCommandDeprecated(name) {}
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
     virtual bool adminOnly() const {
         return true;
diff --git a/src/mongo/db/commands/create_indexes.cpp b/src/mongo/db/commands/create_indexes.cpp
index 036e8dc5148..a38c935163c 100644
--- a/src/mongo/db/commands/create_indexes.cpp
+++ b/src/mongo/db/commands/create_indexes.cpp
@@ -216,9 +216,9 @@ public:
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
         return true;
     }
-    virtual bool slaveOk() const {
-        return false;
-    }  // TODO: this could be made true...
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
+    }
 
     virtual Status checkAuthForCommand(Client* client,
                                        const std::string& dbname,
diff --git a/src/mongo/db/commands/current_op_common.h b/src/mongo/db/commands/current_op_common.h
index 517d494d851..367fb7f0ba8 100644
--- a/src/mongo/db/commands/current_op_common.h
+++ b/src/mongo/db/commands/current_op_common.h
@@ -51,8 +51,8 @@ public:
         return false;
     }
 
-    bool slaveOk() const final {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const final {
+        return AllowedOnSecondary::kAlways;
     }
 
     bool adminOnly() const final {
diff --git a/src/mongo/db/commands/dbcheck.cpp b/src/mongo/db/commands/dbcheck.cpp
index 15b6e6cd516..3cbc2abe362 100644
--- a/src/mongo/db/commands/dbcheck.cpp
+++ b/src/mongo/db/commands/dbcheck.cpp
@@ -489,8 +489,8 @@ class DbCheckCmd : public BasicCommand {
 public:
     DbCheckCmd() : BasicCommand("dbCheck") {}
 
-    virtual bool slaveOk() const {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
     virtual bool adminOnly() const {
diff --git a/src/mongo/db/commands/dbcommands.cpp b/src/mongo/db/commands/dbcommands.cpp
index b46512cd7e2..8f25ddcc13d 100644
--- a/src/mongo/db/commands/dbcommands.cpp
+++ b/src/mongo/db/commands/dbcommands.cpp
@@ -147,8 +147,8 @@ public:
     std::string help() const override {
         return "drop (delete) this database";
     }
-    virtual bool slaveOk() const {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
     virtual void addRequiredPrivileges(const std::string& dbname,
@@ -210,8 +210,8 @@ public:
 
 class CmdRepairDatabase : public ErrmsgCommandDeprecated {
 public:
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
     virtual bool maintenanceMode() const {
         return true;
@@ -295,8 +295,8 @@ public:
 */
 class CmdProfile : public ErrmsgCommandDeprecated {
 public:
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
 
     std::string help() const override {
@@ -396,8 +396,8 @@ public:
 class CmdDrop : public ErrmsgCommandDeprecated {
 public:
     CmdDrop() : ErrmsgCommandDeprecated("drop") {}
-    virtual bool slaveOk() const {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
     virtual bool adminOnly() const {
         return false;
@@ -452,8 +452,8 @@ public:
 class CmdCreate : public BasicCommand {
 public:
     CmdCreate() : BasicCommand("create") {}
-    virtual bool slaveOk() const {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
     virtual bool adminOnly() const {
         return false;
@@ -570,8 +570,8 @@ class CmdFileMD5 : public BasicCommand {
 public:
     CmdFileMD5() : BasicCommand("filemd5") {}
 
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
 
     std::string help() const override {
@@ -747,8 +747,8 @@ class CmdDatasize : public ErrmsgCommandDeprecated {
 public:
     CmdDatasize() : ErrmsgCommandDeprecated("dataSize", "datasize") {}
 
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
         return false;
@@ -897,8 +897,8 @@ class CollectionStats : public ErrmsgCommandDeprecated {
 public:
     CollectionStats() : ErrmsgCommandDeprecated("collStats", "collstats") {}
 
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
         return false;
@@ -944,8 +944,8 @@ class CollectionModCommand : public BasicCommand {
 public:
     CollectionModCommand() : BasicCommand("collMod") {}
 
-    virtual bool slaveOk() const {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
         return true;
@@ -978,8 +978,8 @@ class DBStats : public ErrmsgCommandDeprecated {
 public:
     DBStats() : ErrmsgCommandDeprecated("dbStats", "dbstats") {}
 
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
         return false;
@@ -1074,8 +1074,8 @@ public:
 class CmdWhatsMyUri : public BasicCommand {
 public:
     CmdWhatsMyUri() : BasicCommand("whatsmyuri") {}
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
         return false;
@@ -1099,8 +1099,8 @@ class AvailableQueryOptions : public BasicCommand {
 public:
     AvailableQueryOptions() : BasicCommand("availableQueryOptions", "availablequeryoptions") {}
 
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
         return false;
diff --git a/src/mongo/db/commands/dbhash.cpp b/src/mongo/db/commands/dbhash.cpp
index 1a006d41298..e16a3068d12 100644
--- a/src/mongo/db/commands/dbhash.cpp
+++ b/src/mongo/db/commands/dbhash.cpp
@@ -62,8 +62,8 @@ public:
         return false;
     }
 
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
 
     virtual void addRequiredPrivileges(const std::string& dbname,
diff --git a/src/mongo/db/commands/distinct.cpp b/src/mongo/db/commands/distinct.cpp
index b12a485d68e..50b05986912 100644
--- a/src/mongo/db/commands/distinct.cpp
+++ b/src/mongo/db/commands/distinct.cpp
@@ -75,12 +75,8 @@ class DistinctCommand : public BasicCommand {
 public:
     DistinctCommand() : BasicCommand("distinct") {}
 
-    virtual bool slaveOk() const {
-        return false;
-    }
-
-    virtual bool slaveOverrideOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kOptIn;
     }
 
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
diff --git a/src/mongo/db/commands/do_txn_cmd.cpp b/src/mongo/db/commands/do_txn_cmd.cpp
index 3193b5ba30d..806d282aa79 100644
--- a/src/mongo/db/commands/do_txn_cmd.cpp
+++ b/src/mongo/db/commands/do_txn_cmd.cpp
@@ -131,8 +131,8 @@ class DoTxnCmd : public BasicCommand {
 public:
     DoTxnCmd() : BasicCommand("doTxn") {}
 
-    bool slaveOk() const override {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
     bool supportsWriteConcern(const BSONObj& cmd) const override {
diff --git a/src/mongo/db/commands/driverHelpers.cpp b/src/mongo/db/commands/driverHelpers.cpp
index 2f1e688aa15..9caef43f7b1 100644
--- a/src/mongo/db/commands/driverHelpers.cpp
+++ b/src/mongo/db/commands/driverHelpers.cpp
@@ -59,11 +59,9 @@ public:
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
         return false;
     }
-    virtual bool slaveOk() const {
-        return true;
-    }
-    virtual bool slaveOverrideOk() const {
-        return true;
+
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
 };
 
diff --git a/src/mongo/db/commands/drop_indexes.cpp b/src/mongo/db/commands/drop_indexes.cpp
index 8f311a94295..11cbed2f00c 100644
--- a/src/mongo/db/commands/drop_indexes.cpp
+++ b/src/mongo/db/commands/drop_indexes.cpp
@@ -66,8 +66,8 @@ using std::vector;
 /* "dropIndexes" is now the preferred form - "deleteIndexes" deprecated */
 class CmdDropIndexes : public BasicCommand {
 public:
-    virtual bool slaveOk() const {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
         return true;
@@ -96,9 +96,9 @@ public:
 
 class CmdReIndex : public ErrmsgCommandDeprecated {
 public:
-    virtual bool slaveOk() const {
-        return true;
-    }  // can reindex on a secondary
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;  // can reindex on a secondary
+    }
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
         return false;
     }
diff --git a/src/mongo/db/commands/end_sessions_command.cpp b/src/mongo/db/commands/end_sessions_command.cpp
index 39383f8e58d..9397d39f841 100644
--- a/src/mongo/db/commands/end_sessions_command.cpp
+++ b/src/mongo/db/commands/end_sessions_command.cpp
@@ -44,8 +44,8 @@ class EndSessionsCommand final : public BasicCommand {
 public:
     EndSessionsCommand() : BasicCommand("endSessions") {}
 
-    bool slaveOk() const override {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
     bool adminOnly() const override {
         return false;
diff --git a/src/mongo/db/commands/eval.cpp b/src/mongo/db/commands/eval.cpp
index 36153a54181..0ae44555037 100644
--- a/src/mongo/db/commands/eval.cpp
+++ b/src/mongo/db/commands/eval.cpp
@@ -154,8 +154,8 @@ bool dbEval(OperationContext* opCtx,
 
 class CmdEval : public ErrmsgCommandDeprecated {
 public:
-    virtual bool slaveOk() const {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
     std::string help() const override {
diff --git a/src/mongo/db/commands/explain_cmd.cpp b/src/mongo/db/commands/explain_cmd.cpp
index 08463e626df..0c5ffb15a06 100644
--- a/src/mongo/db/commands/explain_cmd.cpp
+++ b/src/mongo/db/commands/explain_cmd.cpp
@@ -28,6 +28,7 @@
 
 #include "mongo/platform/basic.h"
 
+#include "mongo/db/command_can_run_here.h"
 #include "mongo/db/commands.h"
 #include "mongo/db/query/explain.h"
 #include "mongo/db/repl/replication_coordinator_global.h"
@@ -62,12 +63,8 @@ public:
     /**
      * Running an explain on a secondary requires explicitly setting slaveOk.
      */
-    virtual bool slaveOk() const {
-        return false;
-    }
-
-    virtual bool slaveOverrideOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kOptIn;
     }
 
     virtual bool maintenanceOk() const {
@@ -149,21 +146,7 @@ public:
             return CommandHelpers::appendCommandStatus(result, explainStatus);
         }
 
-        // Check whether the child command is allowed to run here. TODO: this logic is
-        // copied from Command::execCommand and should be abstracted. Until then, make
-        // sure to keep it up to date.
-        repl::ReplicationCoordinator* replCoord = repl::ReplicationCoordinator::get(opCtx);
-        bool iAmPrimary = replCoord->canAcceptWritesForDatabase_UNSAFE(opCtx, dbname);
-        bool commandCanRunOnSecondary = commToExplain->slaveOk();
-
-        bool commandIsOverriddenToRunOnSecondary = commToExplain->slaveOverrideOk() &&
-            ReadPreferenceSetting::get(opCtx).canRunOnSecondary();
-        bool iAmStandalone = !opCtx->writesAreReplicated();
-
-        const bool canRunHere = iAmPrimary || commandCanRunOnSecondary ||
-            commandIsOverriddenToRunOnSecondary || iAmStandalone;
-
-        if (!canRunHere) {
+        if (!commandCanRunHere(opCtx, dbname, commToExplain)) {
             mongoutils::str::stream ss;
             ss << "Explain's child command cannot run on this node. "
                << "Are you explaining a write command on a secondary?";
diff --git a/src/mongo/db/commands/fail_point_cmd.cpp b/src/mongo/db/commands/fail_point_cmd.cpp
index efb705a7bff..940bc33e6a4 100644
--- a/src/mongo/db/commands/fail_point_cmd.cpp
+++ b/src/mongo/db/commands/fail_point_cmd.cpp
@@ -68,11 +68,10 @@ class FaultInjectCmd : public ErrmsgCommandDeprecated {
 public:
     FaultInjectCmd() : ErrmsgCommandDeprecated("configureFailPoint") {}
 
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
 
-
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
         return false;
     }
diff --git a/src/mongo/db/commands/find_and_modify.cpp b/src/mongo/db/commands/find_and_modify.cpp
index 1e8193ce4c9..d5ebaf935c5 100644
--- a/src/mongo/db/commands/find_and_modify.cpp
+++ b/src/mongo/db/commands/find_and_modify.cpp
@@ -220,8 +220,8 @@ public:
                "Output is in the \"value\" field\n";
     }
 
-    bool slaveOk() const override {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
     bool supportsReadConcern(const std::string& dbName,
diff --git a/src/mongo/db/commands/find_cmd.cpp b/src/mongo/db/commands/find_cmd.cpp
index 1ce3f931e5b..7139f52175f 100644
--- a/src/mongo/db/commands/find_cmd.cpp
+++ b/src/mongo/db/commands/find_cmd.cpp
@@ -69,12 +69,8 @@ public:
         return false;
     }
 
-    bool slaveOk() const override {
-        return false;
-    }
-
-    bool slaveOverrideOk() const override {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kOptIn;
     }
 
     bool maintenanceOk() const override {
diff --git a/src/mongo/db/commands/fsync.cpp b/src/mongo/db/commands/fsync.cpp
index eb2b2d375c7..7c4a3799007 100644
--- a/src/mongo/db/commands/fsync.cpp
+++ b/src/mongo/db/commands/fsync.cpp
@@ -101,8 +101,8 @@ public:
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
         return false;
     }
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
     virtual bool adminOnly() const {
         return true;
@@ -273,8 +273,8 @@ public:
         return false;
     }
 
-    bool slaveOk() const override {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
 
     bool adminOnly() const override {
diff --git a/src/mongo/db/commands/generic.cpp b/src/mongo/db/commands/generic.cpp
index 28394239931..7164b951586 100644
--- a/src/mongo/db/commands/generic.cpp
+++ b/src/mongo/db/commands/generic.cpp
@@ -73,9 +73,11 @@ using std::vector;
 class CmdBuildInfo : public BasicCommand {
 public:
     CmdBuildInfo() : BasicCommand("buildInfo", "buildinfo") {}
-    virtual bool slaveOk() const {
-        return true;
+
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
+
     virtual bool adminOnly() const {
         return false;
     }
@@ -104,8 +106,9 @@ public:
 class PingCommand : public BasicCommand {
 public:
     PingCommand() : BasicCommand("ping") {}
-    virtual bool slaveOk() const {
-        return true;
+
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
     std::string help() const override {
         return "a way to check that the server is alive. responds immediately even if server is "
@@ -138,8 +141,8 @@ public:
     std::string help() const override {
         return "return build level feature settings";
     }
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
         return false;
@@ -169,10 +172,10 @@ public:
 class HostInfoCmd : public BasicCommand {
 public:
     HostInfoCmd() : BasicCommand("hostInfo") {}
-    virtual bool slaveOk() const {
-        return true;
-    }
 
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
+    }
 
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
         return false;
@@ -221,11 +224,8 @@ public:
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
         return false;
     }
-    virtual bool slaveOk() const {
-        return true;
-    }
-    virtual bool adminOnly() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
     virtual void addRequiredPrivileges(const std::string& dbname,
                                        const BSONObj& cmdObj,
@@ -255,8 +255,8 @@ public:
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
         return false;
     }
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
     virtual bool adminOnly() const {
         return false;
@@ -283,11 +283,11 @@ public:
         for (const auto& c : commands) {
             BSONObjBuilder temp(b.subobjStart(c->getName()));
             temp.append("help", c->help());
-            temp.append("slaveOk", c->slaveOk());
+            temp.append("slaveOk", c->secondaryAllowed() == Command::AllowedOnSecondary::kAlways);
             temp.append("adminOnly", c->adminOnly());
             // optionally indicates that the command can be forced to run on a slave/secondary
-            if (c->slaveOverrideOk())
-                temp.append("slaveOverrideOk", c->slaveOverrideOk());
+            if (c->secondaryAllowed() == Command::AllowedOnSecondary::kOptIn)
+                temp.append("slaveOverrideOk", true);
             temp.done();
         }
         b.done();
@@ -297,12 +297,37 @@ public:
 
 } listCommandsCmd;
 
+/* for testing purposes only */
+class CmdForceError : public BasicCommand {
+public:
+    std::string help() const override {
+        return "for testing purposes only.  forces a user assertion exception";
+    }
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
+    }
+    virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
+        return false;
+    }
+    virtual void addRequiredPrivileges(const std::string& dbname,
+                                       const BSONObj& cmdObj,
+                                       std::vector<Privilege>* out) {}  // No auth required
+    CmdForceError() : BasicCommand("forceerror") {}
+    bool run(OperationContext* opCtx,
+             const string& dbnamne,
+             const BSONObj& cmdObj,
+             BSONObjBuilder& result) {
+        LastError::get(cc()).setLastError(10038, "forced error");
+        return false;
+    }
+} cmdForceError;
+
 class GetLogCmd : public ErrmsgCommandDeprecated {
 public:
     GetLogCmd() : ErrmsgCommandDeprecated("getLog") {}
 
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
         return false;
@@ -372,8 +397,8 @@ class ClearLogCmd : public BasicCommand {
 public:
     ClearLogCmd() : BasicCommand("clearLog") {}
 
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
         return false;
@@ -433,8 +458,8 @@ public:
     virtual bool adminOnly() const {
         return true;
     }
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
     virtual void addRequiredPrivileges(const std::string& dbname,
                                        const BSONObj& cmdObj,
diff --git a/src/mongo/db/commands/geo_near_cmd.cpp b/src/mongo/db/commands/geo_near_cmd.cpp
index ac1d839100b..7cf8a3b7e02 100644
--- a/src/mongo/db/commands/geo_near_cmd.cpp
+++ b/src/mongo/db/commands/geo_near_cmd.cpp
@@ -74,11 +74,8 @@ public:
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
         return false;
     }
-    bool slaveOk() const {
-        return true;
-    }
-    bool slaveOverrideOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
     bool supportsReadConcern(const std::string& dbName,
                              const BSONObj& cmdObj,
diff --git a/src/mongo/db/commands/get_last_error.cpp b/src/mongo/db/commands/get_last_error.cpp
index 3d2d6d414c1..0eb1a9939a0 100644
--- a/src/mongo/db/commands/get_last_error.cpp
+++ b/src/mongo/db/commands/get_last_error.cpp
@@ -60,8 +60,8 @@ public:
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
         return false;
     }
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
     virtual void addRequiredPrivileges(const std::string& dbname,
                                        const BSONObj& cmdObj,
@@ -90,8 +90,8 @@ public:
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
         return false;
     }
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
     virtual void addRequiredPrivileges(const std::string& dbname,
                                        const BSONObj& cmdObj,
@@ -313,8 +313,8 @@ public:
     std::string help() const override {
         return "check for errors since last reseterror commandcal";
     }
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
     bool requiresAuth() const override {
         return false;
diff --git a/src/mongo/db/commands/getmore_cmd.cpp b/src/mongo/db/commands/getmore_cmd.cpp
index 594a2886d08..16e5261dbde 100644
--- a/src/mongo/db/commands/getmore_cmd.cpp
+++ b/src/mongo/db/commands/getmore_cmd.cpp
@@ -89,8 +89,8 @@ public:
         return false;
     }
 
-    bool slaveOk() const override {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
 
     bool maintenanceOk() const override {
diff --git a/src/mongo/db/commands/group_cmd.cpp b/src/mongo/db/commands/group_cmd.cpp
index 85b93ec071a..62f9ee7bbb3 100644
--- a/src/mongo/db/commands/group_cmd.cpp
+++ b/src/mongo/db/commands/group_cmd.cpp
@@ -71,12 +71,8 @@ private:
         return false;
     }
 
-    virtual bool slaveOk() const {
-        return false;
-    }
-
-    virtual bool slaveOverrideOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kOptIn;
     }
 
     bool supportsReadConcern(const std::string& dbName,
diff --git a/src/mongo/db/commands/hashcmd.cpp b/src/mongo/db/commands/hashcmd.cpp
index f65fda66d84..021ccfd573a 100644
--- a/src/mongo/db/commands/hashcmd.cpp
+++ b/src/mongo/db/commands/hashcmd.cpp
@@ -56,8 +56,8 @@ public:
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
         return false;
     }
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
     // No auth needed because it only works when enabled via command line.
     virtual void addRequiredPrivileges(const std::string& dbname,
diff --git a/src/mongo/db/commands/haystack.cpp b/src/mongo/db/commands/haystack.cpp
index 18f3b1d1edc..61ccbbb00bc 100644
--- a/src/mongo/db/commands/haystack.cpp
+++ b/src/mongo/db/commands/haystack.cpp
@@ -68,12 +68,8 @@ public:
         return false;
     }
 
-    bool slaveOk() const {
-        return true;
-    }
-
-    bool slaveOverrideOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
 
     bool supportsReadConcern(const std::string& dbName,
diff --git a/src/mongo/db/commands/index_filter_commands.cpp b/src/mongo/db/commands/index_filter_commands.cpp
index 1eaeadcd656..5bbae6c6de0 100644
--- a/src/mongo/db/commands/index_filter_commands.cpp
+++ b/src/mongo/db/commands/index_filter_commands.cpp
@@ -129,12 +129,8 @@ bool IndexFilterCommand::supportsWriteConcern(const BSONObj& cmd) const {
     return false;
 }
 
-bool IndexFilterCommand::slaveOk() const {
-    return false;
-}
-
-bool IndexFilterCommand::slaveOverrideOk() const {
-    return true;
+Command::AllowedOnSecondary IndexFilterCommand::secondaryAllowed() const {
+    return AllowedOnSecondary::kOptIn;
 }
 
 std::string IndexFilterCommand::help() const {
diff --git a/src/mongo/db/commands/index_filter_commands.h b/src/mongo/db/commands/index_filter_commands.h
index aaa785c0d6b..72f758806c5 100644
--- a/src/mongo/db/commands/index_filter_commands.h
+++ b/src/mongo/db/commands/index_filter_commands.h
@@ -70,9 +70,7 @@ public:
 
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override;
 
-    virtual bool slaveOk() const;
-
-    virtual bool slaveOverrideOk() const;
+    AllowedOnSecondary secondaryAllowed() const override;
 
     std::string help() const override;
 
diff --git a/src/mongo/db/commands/isself.cpp b/src/mongo/db/commands/isself.cpp
index 841dfde9e54..e3c7d077aae 100644
--- a/src/mongo/db/commands/isself.cpp
+++ b/src/mongo/db/commands/isself.cpp
@@ -42,8 +42,8 @@ using std::stringstream;
 class IsSelfCommand : public BasicCommand {
 public:
     IsSelfCommand() : BasicCommand("_isSelf") {}
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
         return false;
diff --git a/src/mongo/db/commands/kill_all_sessions_by_pattern_command.cpp b/src/mongo/db/commands/kill_all_sessions_by_pattern_command.cpp
index 708cb67d34b..645c5e83c2c 100644
--- a/src/mongo/db/commands/kill_all_sessions_by_pattern_command.cpp
+++ b/src/mongo/db/commands/kill_all_sessions_by_pattern_command.cpp
@@ -57,8 +57,8 @@ class KillAllSessionsByPatternCommand final : public BasicCommand {
 public:
     KillAllSessionsByPatternCommand() : BasicCommand("killAllSessionsByPattern") {}
 
-    bool slaveOk() const override {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
     bool adminOnly() const override {
         return false;
diff --git a/src/mongo/db/commands/kill_all_sessions_command.cpp b/src/mongo/db/commands/kill_all_sessions_command.cpp
index 86f0a629249..4605a5f1964 100644
--- a/src/mongo/db/commands/kill_all_sessions_command.cpp
+++ b/src/mongo/db/commands/kill_all_sessions_command.cpp
@@ -57,8 +57,8 @@ class KillAllSessionsCommand final : public BasicCommand {
 public:
     KillAllSessionsCommand() : BasicCommand("killAllSessions") {}
 
-    bool slaveOk() const override {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
     bool adminOnly() const override {
         return false;
diff --git a/src/mongo/db/commands/kill_op.cpp b/src/mongo/db/commands/kill_op.cpp
index 7b07c87f7ba..8cc2754e919 100644
--- a/src/mongo/db/commands/kill_op.cpp
+++ b/src/mongo/db/commands/kill_op.cpp
@@ -55,8 +55,8 @@ public:
         return false;
     }
 
-    bool slaveOk() const final {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
 
     bool adminOnly() const final {
diff --git a/src/mongo/db/commands/kill_sessions_command.cpp b/src/mongo/db/commands/kill_sessions_command.cpp
index 0be33339f25..55f8dfc1a2d 100644
--- a/src/mongo/db/commands/kill_sessions_command.cpp
+++ b/src/mongo/db/commands/kill_sessions_command.cpp
@@ -84,8 +84,8 @@ class KillSessionsCommand final : public BasicCommand {
 public:
     KillSessionsCommand() : BasicCommand("killSessions") {}
 
-    bool slaveOk() const override {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
     bool adminOnly() const override {
         return false;
diff --git a/src/mongo/db/commands/killcursors_common.h b/src/mongo/db/commands/killcursors_common.h
index 6991a4a0da7..90541adc709 100644
--- a/src/mongo/db/commands/killcursors_common.h
+++ b/src/mongo/db/commands/killcursors_common.h
@@ -45,8 +45,8 @@ public:
         return false;
     }
 
-    bool slaveOk() const final {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
 
     bool maintenanceOk() const final {
diff --git a/src/mongo/db/commands/list_collections.cpp b/src/mongo/db/commands/list_collections.cpp
index b21c0f959a1..b92c59034ba 100644
--- a/src/mongo/db/commands/list_collections.cpp
+++ b/src/mongo/db/commands/list_collections.cpp
@@ -197,11 +197,8 @@ BSONObj buildCollectionBson(OperationContext* opCtx,
 
 class CmdListCollections : public BasicCommand {
 public:
-    virtual bool slaveOk() const {
-        return false;
-    }
-    virtual bool slaveOverrideOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kOptIn;
     }
     virtual bool adminOnly() const {
         return false;
diff --git a/src/mongo/db/commands/list_databases.cpp b/src/mongo/db/commands/list_databases.cpp
index f91cb10f680..99bc8166021 100644
--- a/src/mongo/db/commands/list_databases.cpp
+++ b/src/mongo/db/commands/list_databases.cpp
@@ -57,11 +57,8 @@ intmax_t dbSize(const string& database);
 
 class CmdListDatabases : public BasicCommand {
 public:
-    bool slaveOk() const final {
-        return false;
-    }
-    bool slaveOverrideOk() const final {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const final {
+        return AllowedOnSecondary::kOptIn;
     }
     bool adminOnly() const final {
         return true;
diff --git a/src/mongo/db/commands/list_indexes.cpp b/src/mongo/db/commands/list_indexes.cpp
index 5c23ea9f1c6..cef7130a20c 100644
--- a/src/mongo/db/commands/list_indexes.cpp
+++ b/src/mongo/db/commands/list_indexes.cpp
@@ -76,11 +76,8 @@ namespace {
  */
 class CmdListIndexes : public BasicCommand {
 public:
-    virtual bool slaveOk() const {
-        return false;
-    }
-    virtual bool slaveOverrideOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kOptIn;
     }
     virtual bool adminOnly() const {
         return false;
diff --git a/src/mongo/db/commands/lock_info.cpp b/src/mongo/db/commands/lock_info.cpp
index 6bd6aeb3258..3e16e220e39 100644
--- a/src/mongo/db/commands/lock_info.cpp
+++ b/src/mongo/db/commands/lock_info.cpp
@@ -49,12 +49,8 @@ using std::stringstream;
  */
 class CmdLockInfo : public BasicCommand {
 public:
-    virtual bool slaveOk() const {
-        return true;
-    }
-
-    virtual bool slaveOverrideOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
 
     virtual bool adminOnly() const {
diff --git a/src/mongo/db/commands/mr.cpp b/src/mongo/db/commands/mr.cpp
index ef9043fd78a..ce7d144bfcc 100644
--- a/src/mongo/db/commands/mr.cpp
+++ b/src/mongo/db/commands/mr.cpp
@@ -1351,13 +1351,12 @@ class MapReduceCommand : public ErrmsgCommandDeprecated {
 public:
     MapReduceCommand() : ErrmsgCommandDeprecated("mapReduce", "mapreduce") {}
 
-    virtual bool slaveOk() const {
-        return repl::getGlobalReplicationCoordinator()->getReplicationMode() !=
-            repl::ReplicationCoordinator::modeReplSet;
-    }
-
-    virtual bool slaveOverrideOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        if (repl::getGlobalReplicationCoordinator()->getReplicationMode() !=
+            repl::ReplicationCoordinator::modeReplSet) {
+            return AllowedOnSecondary::kAlways;
+        }
+        return AllowedOnSecondary::kOptIn;
     }
 
     std::size_t reserveBytesForReply() const override {
@@ -1689,13 +1688,15 @@ public:
         return "internal";
     }
     MapReduceFinishCommand() : BasicCommand("mapreduce.shardedfinish") {}
-    virtual bool slaveOk() const {
-        return repl::getGlobalReplicationCoordinator()->getReplicationMode() !=
-            repl::ReplicationCoordinator::modeReplSet;
-    }
-    virtual bool slaveOverrideOk() const {
-        return true;
+
+    AllowedOnSecondary secondaryAllowed() const override {
+        if (repl::getGlobalReplicationCoordinator()->getReplicationMode() !=
+            repl::ReplicationCoordinator::modeReplSet) {
+            return AllowedOnSecondary::kAlways;
+        }
+        return AllowedOnSecondary::kOptIn;
     }
+
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
         return true;
     }
diff --git a/src/mongo/db/commands/oplog_note.cpp b/src/mongo/db/commands/oplog_note.cpp
index 9b26b979ba6..2f1d06b79b5 100644
--- a/src/mongo/db/commands/oplog_note.cpp
+++ b/src/mongo/db/commands/oplog_note.cpp
@@ -87,8 +87,8 @@ class AppendOplogNoteCmd : public BasicCommand {
 public:
     AppendOplogNoteCmd() : BasicCommand("appendOplogNote") {}
 
-    virtual bool slaveOk() const {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
     virtual bool adminOnly() const {
diff --git a/src/mongo/db/commands/parallel_collection_scan.cpp b/src/mongo/db/commands/parallel_collection_scan.cpp
index 783e74be716..c9f36a820e4 100644
--- a/src/mongo/db/commands/parallel_collection_scan.cpp
+++ b/src/mongo/db/commands/parallel_collection_scan.cpp
@@ -62,8 +62,8 @@ public:
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
         return false;
     }
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
 
     bool supportsReadConcern(const std::string& dbName,
diff --git a/src/mongo/db/commands/parameters.cpp b/src/mongo/db/commands/parameters.cpp
index 7e03b90985b..391a1ffded8 100644
--- a/src/mongo/db/commands/parameters.cpp
+++ b/src/mongo/db/commands/parameters.cpp
@@ -67,8 +67,8 @@ void appendParameterNames(std::string* help) {
 class CmdGet : public ErrmsgCommandDeprecated {
 public:
     CmdGet() : ErrmsgCommandDeprecated("getParameter") {}
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
     virtual bool adminOnly() const {
         return true;
@@ -118,8 +118,8 @@ public:
 class CmdSet : public ErrmsgCommandDeprecated {
 public:
     CmdSet() : ErrmsgCommandDeprecated("setParameter") {}
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
     virtual bool adminOnly() const {
         return true;
diff --git a/src/mongo/db/commands/pipeline_command.cpp b/src/mongo/db/commands/pipeline_command.cpp
index 8ec12102c35..ae607f2713f 100644
--- a/src/mongo/db/commands/pipeline_command.cpp
+++ b/src/mongo/db/commands/pipeline_command.cpp
@@ -57,12 +57,8 @@ public:
         return Pipeline::aggSupportsWriteConcern(cmd);
     }
 
-    bool slaveOk() const override {
-        return false;
-    }
-
-    bool slaveOverrideOk() const override {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kOptIn;
     }
 
     bool supportsReadConcern(const std::string& dbName,
diff --git a/src/mongo/db/commands/plan_cache_commands.cpp b/src/mongo/db/commands/plan_cache_commands.cpp
index 0cd3593f5c1..a76100a90c7 100644
--- a/src/mongo/db/commands/plan_cache_commands.cpp
+++ b/src/mongo/db/commands/plan_cache_commands.cpp
@@ -124,12 +124,8 @@ bool PlanCacheCommand::supportsWriteConcern(const BSONObj& cmd) const {
     return false;
 }
 
-bool PlanCacheCommand::slaveOk() const {
-    return false;
-}
-
-bool PlanCacheCommand::slaveOverrideOk() const {
-    return true;
+Command::AllowedOnSecondary PlanCacheCommand::secondaryAllowed() const {
+    return AllowedOnSecondary::kOptIn;
 }
 
 std::string PlanCacheCommand::help() const {
diff --git a/src/mongo/db/commands/plan_cache_commands.h b/src/mongo/db/commands/plan_cache_commands.h
index 0b0a680b2da..c883a189820 100644
--- a/src/mongo/db/commands/plan_cache_commands.h
+++ b/src/mongo/db/commands/plan_cache_commands.h
@@ -64,9 +64,7 @@ public:
 
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override;
 
-    virtual bool slaveOk() const;
-
-    virtual bool slaveOverrideOk() const;
+    AllowedOnSecondary secondaryAllowed() const override;
 
     std::string help() const override;
 
diff --git a/src/mongo/db/commands/reap_logical_session_cache_now.cpp b/src/mongo/db/commands/reap_logical_session_cache_now.cpp
index 879952791fc..f04ee086359 100644
--- a/src/mongo/db/commands/reap_logical_session_cache_now.cpp
+++ b/src/mongo/db/commands/reap_logical_session_cache_now.cpp
@@ -44,8 +44,8 @@ class ReapLogicalSessionCacheNowCommand final : public BasicCommand {
 public:
     ReapLogicalSessionCacheNowCommand() : BasicCommand("reapLogicalSessionCacheNow") {}
 
-    bool slaveOk() const override {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
 
     bool adminOnly() const override {
diff --git a/src/mongo/db/commands/refresh_logical_session_cache_now.cpp b/src/mongo/db/commands/refresh_logical_session_cache_now.cpp
index 5dcbe213eaa..ff3e018eede 100644
--- a/src/mongo/db/commands/refresh_logical_session_cache_now.cpp
+++ b/src/mongo/db/commands/refresh_logical_session_cache_now.cpp
@@ -45,8 +45,8 @@ class RefreshLogicalSessionCacheNowCommand final : public BasicCommand {
 public:
     RefreshLogicalSessionCacheNowCommand() : BasicCommand("refreshLogicalSessionCacheNow") {}
 
-    bool slaveOk() const override {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
 
     bool adminOnly() const override {
diff --git a/src/mongo/db/commands/refresh_sessions_command.cpp b/src/mongo/db/commands/refresh_sessions_command.cpp
index 4db76567261..0570821ca1e 100644
--- a/src/mongo/db/commands/refresh_sessions_command.cpp
+++ b/src/mongo/db/commands/refresh_sessions_command.cpp
@@ -46,8 +46,8 @@ class RefreshSessionsCommand final : public BasicCommand {
 public:
     RefreshSessionsCommand() : BasicCommand("refreshSessions") {}
 
-    bool slaveOk() const override {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
     bool adminOnly() const override {
         return false;
diff --git a/src/mongo/db/commands/refresh_sessions_command_internal.cpp b/src/mongo/db/commands/refresh_sessions_command_internal.cpp
index 1cfbf7deeb0..fa52de2caec 100644
--- a/src/mongo/db/commands/refresh_sessions_command_internal.cpp
+++ b/src/mongo/db/commands/refresh_sessions_command_internal.cpp
@@ -46,8 +46,8 @@ class RefreshSessionsCommandInternal final : public BasicCommand {
 public:
     RefreshSessionsCommandInternal() : BasicCommand("refreshSessionsInternal") {}
 
-    bool slaveOk() const override {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
     bool adminOnly() const override {
         return false;
diff --git a/src/mongo/db/commands/rename_collection_cmd.cpp b/src/mongo/db/commands/rename_collection_cmd.cpp
index 144ecbf847e..01cba8c386a 100644
--- a/src/mongo/db/commands/rename_collection_cmd.cpp
+++ b/src/mongo/db/commands/rename_collection_cmd.cpp
@@ -62,8 +62,8 @@ public:
     virtual bool adminOnly() const {
         return true;
     }
-    virtual bool slaveOk() const {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
         return true;
diff --git a/src/mongo/db/commands/repair_cursor.cpp b/src/mongo/db/commands/repair_cursor.cpp
index 51567abbabc..12c4cfa3528 100644
--- a/src/mongo/db/commands/repair_cursor.cpp
+++ b/src/mongo/db/commands/repair_cursor.cpp
@@ -52,8 +52,8 @@ public:
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
         return false;
     }
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
 
     virtual Status checkAuthForCommand(Client* client,
diff --git a/src/mongo/db/commands/resize_oplog.cpp b/src/mongo/db/commands/resize_oplog.cpp
index 4373c9c9dd5..ef853e9bb17 100644
--- a/src/mongo/db/commands/resize_oplog.cpp
+++ b/src/mongo/db/commands/resize_oplog.cpp
@@ -54,8 +54,8 @@ class CmdReplSetResizeOplog : public BasicCommand {
 public:
     CmdReplSetResizeOplog() : BasicCommand("replSetResizeOplog") {}
 
-    virtual bool slaveOk() const final {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
 
     bool adminOnly() const final {
diff --git a/src/mongo/db/commands/server_status.cpp b/src/mongo/db/commands/server_status.cpp
index a4b63e778f2..98aefce2f62 100644
--- a/src/mongo/db/commands/server_status.cpp
+++ b/src/mongo/db/commands/server_status.cpp
@@ -72,8 +72,8 @@ public:
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
         return false;
     }
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
     virtual bool allowsAfterClusterTime(const BSONObj& cmdObj) const override {
         return false;
diff --git a/src/mongo/db/commands/set_feature_compatibility_version_command.cpp b/src/mongo/db/commands/set_feature_compatibility_version_command.cpp
index 31e28b6a5b5..b4f58018eaa 100644
--- a/src/mongo/db/commands/set_feature_compatibility_version_command.cpp
+++ b/src/mongo/db/commands/set_feature_compatibility_version_command.cpp
@@ -69,8 +69,8 @@ public:
     SetFeatureCompatibilityVersionCommand()
         : BasicCommand(FeatureCompatibilityVersion::kCommandName) {}
 
-    virtual bool slaveOk() const {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
     virtual bool adminOnly() const {
diff --git a/src/mongo/db/commands/shutdown.h b/src/mongo/db/commands/shutdown.h
index 655d25b367f..e89aa301261 100644
--- a/src/mongo/db/commands/shutdown.h
+++ b/src/mongo/db/commands/shutdown.h
@@ -48,8 +48,8 @@ public:
     virtual bool localHostOnlyIfNoAuth() {
         return true;
     }
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
     virtual void addRequiredPrivileges(const std::string& dbname,
                                        const BSONObj& cmdObj,
diff --git a/src/mongo/db/commands/snapshot_management.cpp b/src/mongo/db/commands/snapshot_management.cpp
index 3661447d224..096cdbf2582 100644
--- a/src/mongo/db/commands/snapshot_management.cpp
+++ b/src/mongo/db/commands/snapshot_management.cpp
@@ -44,8 +44,8 @@ class CmdMakeSnapshot final : public BasicCommand {
 public:
     CmdMakeSnapshot() : BasicCommand("makeSnapshot") {}
 
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
         return false;
@@ -92,8 +92,8 @@ class CmdSetCommittedSnapshot final : public BasicCommand {
 public:
     CmdSetCommittedSnapshot() : BasicCommand("setCommittedSnapshot") {}
 
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
         return false;
diff --git a/src/mongo/db/commands/start_session_command.cpp b/src/mongo/db/commands/start_session_command.cpp
index b621ca02237..a577cc01cb7 100644
--- a/src/mongo/db/commands/start_session_command.cpp
+++ b/src/mongo/db/commands/start_session_command.cpp
@@ -51,8 +51,8 @@ class StartSessionCommand final : public BasicCommand {
 public:
     StartSessionCommand() : BasicCommand("startSession") {}
 
-    bool slaveOk() const override {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
     bool adminOnly() const override {
         return false;
diff --git a/src/mongo/db/commands/test_commands.cpp b/src/mongo/db/commands/test_commands.cpp
index 1615117783e..c7c7c5db1a4 100644
--- a/src/mongo/db/commands/test_commands.cpp
+++ b/src/mongo/db/commands/test_commands.cpp
@@ -62,8 +62,8 @@ public:
     virtual bool adminOnly() const {
         return false;
     }
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
         return true;
@@ -118,8 +118,8 @@ public:
         return true;
     }
 
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
 
     std::string help() const override {
@@ -201,8 +201,8 @@ public:
 class CapTrunc : public BasicCommand {
 public:
     CapTrunc() : BasicCommand("captrunc") {}
-    virtual bool slaveOk() const {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
         return true;
@@ -276,8 +276,8 @@ public:
 class EmptyCapped : public BasicCommand {
 public:
     EmptyCapped() : BasicCommand("emptycapped") {}
-    virtual bool slaveOk() const {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
         return true;
diff --git a/src/mongo/db/commands/top_command.cpp b/src/mongo/db/commands/top_command.cpp
index 241c44e5702..d7691005285 100644
--- a/src/mongo/db/commands/top_command.cpp
+++ b/src/mongo/db/commands/top_command.cpp
@@ -46,8 +46,8 @@ class TopCommand : public BasicCommand {
 public:
     TopCommand() : BasicCommand("top") {}
 
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
     virtual bool adminOnly() const {
         return true;
diff --git a/src/mongo/db/commands/touch.cpp b/src/mongo/db/commands/touch.cpp
index d9c2651f34d..2423c3ae6bd 100644
--- a/src/mongo/db/commands/touch.cpp
+++ b/src/mongo/db/commands/touch.cpp
@@ -61,8 +61,8 @@ public:
     virtual bool adminOnly() const {
         return false;
     }
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
     virtual bool maintenanceMode() const {
         return true;
diff --git a/src/mongo/db/commands/user_management_commands.cpp b/src/mongo/db/commands/user_management_commands.cpp
index 9ccf077f479..7aafdce777b 100644
--- a/src/mongo/db/commands/user_management_commands.cpp
+++ b/src/mongo/db/commands/user_management_commands.cpp
@@ -611,8 +611,8 @@ class CmdCreateUser : public BasicCommand {
 public:
     CmdCreateUser() : BasicCommand("createUser") {}
 
-    virtual bool slaveOk() const {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
@@ -758,8 +758,8 @@ class CmdUpdateUser : public BasicCommand {
 public:
     CmdUpdateUser() : BasicCommand("updateUser") {}
 
-    virtual bool slaveOk() const {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
@@ -892,8 +892,8 @@ class CmdDropUser : public BasicCommand {
 public:
     CmdDropUser() : BasicCommand("dropUser") {}
 
-    virtual bool slaveOk() const {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
@@ -959,8 +959,8 @@ class CmdDropAllUsersFromDatabase : public BasicCommand {
 public:
     CmdDropAllUsersFromDatabase() : BasicCommand("dropAllUsersFromDatabase") {}
 
-    virtual bool slaveOk() const {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
@@ -1015,8 +1015,8 @@ class CmdGrantRolesToUser : public BasicCommand {
 public:
     CmdGrantRolesToUser() : BasicCommand("grantRolesToUser") {}
 
-    virtual bool slaveOk() const {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
@@ -1087,8 +1087,8 @@ class CmdRevokeRolesFromUser : public BasicCommand {
 public:
     CmdRevokeRolesFromUser() : BasicCommand("revokeRolesFromUser") {}
 
-    virtual bool slaveOk() const {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
@@ -1157,12 +1157,8 @@ public:
 
 class CmdUsersInfo : public BasicCommand {
 public:
-    virtual bool slaveOk() const {
-        return false;
-    }
-
-    virtual bool slaveOverrideOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kOptIn;
     }
 
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
@@ -1285,8 +1281,8 @@ class CmdCreateRole : public BasicCommand {
 public:
     CmdCreateRole() : BasicCommand("createRole") {}
 
-    virtual bool slaveOk() const {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
@@ -1406,8 +1402,8 @@ class CmdUpdateRole : public BasicCommand {
 public:
     CmdUpdateRole() : BasicCommand("updateRole") {}
 
-    virtual bool slaveOk() const {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
@@ -1523,8 +1519,8 @@ class CmdGrantPrivilegesToRole : public BasicCommand {
 public:
     CmdGrantPrivilegesToRole() : BasicCommand("grantPrivilegesToRole") {}
 
-    virtual bool slaveOk() const {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
@@ -1633,8 +1629,8 @@ class CmdRevokePrivilegesFromRole : public BasicCommand {
 public:
     CmdRevokePrivilegesFromRole() : BasicCommand("revokePrivilegesFromRole") {}
 
-    virtual bool slaveOk() const {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
@@ -1745,8 +1741,8 @@ class CmdGrantRolesToRole : public BasicCommand {
 public:
     CmdGrantRolesToRole() : BasicCommand("grantRolesToRole") {}
 
-    virtual bool slaveOk() const {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
@@ -1834,8 +1830,8 @@ class CmdRevokeRolesFromRole : public BasicCommand {
 public:
     CmdRevokeRolesFromRole() : BasicCommand("revokeRolesFromRole") {}
 
-    virtual bool slaveOk() const {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
@@ -1918,8 +1914,8 @@ class CmdDropRole : public BasicCommand {
 public:
     CmdDropRole() : BasicCommand("dropRole") {}
 
-    virtual bool slaveOk() const {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
@@ -2060,8 +2056,8 @@ class CmdDropAllRolesFromDatabase : public BasicCommand {
 public:
     CmdDropAllRolesFromDatabase() : BasicCommand("dropAllRolesFromDatabase") {}
 
-    virtual bool slaveOk() const {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
@@ -2191,12 +2187,8 @@ public:
 
 class CmdRolesInfo : public BasicCommand {
 public:
-    virtual bool slaveOk() const {
-        return false;
-    }
-
-    virtual bool slaveOverrideOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kOptIn;
     }
 
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
@@ -2280,8 +2272,8 @@ public:
 
 class CmdInvalidateUserCache : public BasicCommand {
 public:
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
 
     virtual bool adminOnly() const {
@@ -2317,8 +2309,8 @@ public:
 
 class CmdGetCacheGeneration : public BasicCommand {
 public:
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
 
     virtual bool adminOnly() const {
@@ -2366,8 +2358,8 @@ class CmdMergeAuthzCollections : public BasicCommand {
 public:
     CmdMergeAuthzCollections() : BasicCommand("_mergeAuthzCollections") {}
 
-    virtual bool slaveOk() const {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
diff --git a/src/mongo/db/commands/validate.cpp b/src/mongo/db/commands/validate.cpp
index f3d04650286..1ef643d87cf 100644
--- a/src/mongo/db/commands/validate.cpp
+++ b/src/mongo/db/commands/validate.cpp
@@ -67,8 +67,8 @@ class ValidateCmd : public BasicCommand {
 public:
     ValidateCmd() : BasicCommand("validate") {}
 
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
 
     std::string help() const override {
diff --git a/src/mongo/db/commands/write_commands/write_commands.cpp b/src/mongo/db/commands/write_commands/write_commands.cpp
index 922c5a57652..ac0a73dee89 100644
--- a/src/mongo/db/commands/write_commands/write_commands.cpp
+++ b/src/mongo/db/commands/write_commands/write_commands.cpp
@@ -198,8 +198,8 @@ class WriteCommand : public Command {
 public:
     explicit WriteCommand(StringData name) : Command(name) {}
 
-    bool slaveOk() const final {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const final {
+        return AllowedOnSecondary::kNever;
     }
 
     bool shouldAffectCommandCounter() const final {
diff --git a/src/mongo/db/exec/stagedebug_cmd.cpp b/src/mongo/db/exec/stagedebug_cmd.cpp
index df3e78671df..642bdf4f5b1 100644
--- a/src/mongo/db/exec/stagedebug_cmd.cpp
+++ b/src/mongo/db/exec/stagedebug_cmd.cpp
@@ -123,11 +123,8 @@ public:
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
         return false;
     }
-    bool slaveOk() const {
-        return false;
-    }
-    bool slaveOverrideOk() const {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
     std::string help() const override {
         return {};
diff --git a/src/mongo/db/ftdc/ftdc_commands.cpp b/src/mongo/db/ftdc/ftdc_commands.cpp
index 3bd4a75e256..c4067f6ca44 100644
--- a/src/mongo/db/ftdc/ftdc_commands.cpp
+++ b/src/mongo/db/ftdc/ftdc_commands.cpp
@@ -57,8 +57,8 @@ public:
         return "get latest diagnostic data collection snapshot";
     }
 
-    bool slaveOk() const override {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
 
     bool supportsWriteConcern(const BSONObj& cmd) const override {
diff --git a/src/mongo/db/repl/master_slave.cpp b/src/mongo/db/repl/master_slave.cpp
index c0e22a2221a..131bc3b21c9 100644
--- a/src/mongo/db/repl/master_slave.cpp
+++ b/src/mongo/db/repl/master_slave.cpp
@@ -368,8 +368,8 @@ public:
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
         return false;
     }
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
     virtual bool adminOnly() const {
         return false;
diff --git a/src/mongo/db/repl/repl_set_command.h b/src/mongo/db/repl/repl_set_command.h
index fd43ad1c8b2..ad97ff5e8b9 100644
--- a/src/mongo/db/repl/repl_set_command.h
+++ b/src/mongo/db/repl/repl_set_command.h
@@ -47,8 +47,8 @@ class ReplSetCommand : public BasicCommand {
 protected:
     ReplSetCommand(const char* s) : BasicCommand(s) {}
 
-    bool slaveOk() const override {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
 
     bool adminOnly() const override {
diff --git a/src/mongo/db/repl/replication_info.cpp b/src/mongo/db/repl/replication_info.cpp
index 69c969231ce..0911a180d36 100644
--- a/src/mongo/db/repl/replication_info.cpp
+++ b/src/mongo/db/repl/replication_info.cpp
@@ -216,8 +216,8 @@ public:
     bool requiresAuth() const override {
         return false;
     }
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
     std::string help() const override {
         return "Check if this server is primary for a replica pair/set; also if it is --master or "
diff --git a/src/mongo/db/repl/resync.cpp b/src/mongo/db/repl/resync.cpp
index ccc566d63c3..9b3fab10d2b 100644
--- a/src/mongo/db/repl/resync.cpp
+++ b/src/mongo/db/repl/resync.cpp
@@ -49,8 +49,8 @@ constexpr StringData kWaitFieldName = "wait"_sd;
 // operator requested resynchronization of replication (on a slave or secondary). {resync: 1}
 class CmdResync : public ErrmsgCommandDeprecated {
 public:
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
     virtual bool adminOnly() const {
         return true;
diff --git a/src/mongo/db/s/check_sharding_index_command.cpp b/src/mongo/db/s/check_sharding_index_command.cpp
index 9d3afd68c8e..04414dc9051 100644
--- a/src/mongo/db/s/check_sharding_index_command.cpp
+++ b/src/mongo/db/s/check_sharding_index_command.cpp
@@ -67,8 +67,8 @@ public:
         return false;
     }
 
-    virtual bool slaveOk() const {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
     virtual void addRequiredPrivileges(const std::string& dbname,
diff --git a/src/mongo/db/s/cleanup_orphaned_cmd.cpp b/src/mongo/db/s/cleanup_orphaned_cmd.cpp
index afadefadbd4..9b338b0731e 100644
--- a/src/mongo/db/s/cleanup_orphaned_cmd.cpp
+++ b/src/mongo/db/s/cleanup_orphaned_cmd.cpp
@@ -164,8 +164,8 @@ class CleanupOrphanedCommand : public ErrmsgCommandDeprecated {
 public:
     CleanupOrphanedCommand() : ErrmsgCommandDeprecated("cleanupOrphaned") {}
 
-    bool slaveOk() const override {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
     bool adminOnly() const override {
diff --git a/src/mongo/db/s/config/configsvr_add_shard_command.cpp b/src/mongo/db/s/config/configsvr_add_shard_command.cpp
index c6354590788..834aa73ca74 100644
--- a/src/mongo/db/s/config/configsvr_add_shard_command.cpp
+++ b/src/mongo/db/s/config/configsvr_add_shard_command.cpp
@@ -65,8 +65,8 @@ public:
                "directly. Validates and adds a new shard to the cluster.";
     }
 
-    bool slaveOk() const override {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
     bool adminOnly() const override {
diff --git a/src/mongo/db/s/config/configsvr_add_shard_to_zone_command.cpp b/src/mongo/db/s/config/configsvr_add_shard_to_zone_command.cpp
index 391aa557867..00c1af987cf 100644
--- a/src/mongo/db/s/config/configsvr_add_shard_to_zone_command.cpp
+++ b/src/mongo/db/s/config/configsvr_add_shard_to_zone_command.cpp
@@ -65,8 +65,8 @@ public:
                "directly. Validates and adds a new zone to the shard.";
     }
 
-    bool slaveOk() const override {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
     bool adminOnly() const override {
diff --git a/src/mongo/db/s/config/configsvr_commit_chunk_migration_command.cpp b/src/mongo/db/s/config/configsvr_commit_chunk_migration_command.cpp
index 134032e61c4..4e9b80d82ea 100644
--- a/src/mongo/db/s/config/configsvr_commit_chunk_migration_command.cpp
+++ b/src/mongo/db/s/config/configsvr_commit_chunk_migration_command.cpp
@@ -91,8 +91,8 @@ public:
         return "should not be calling this directly";
     }
 
-    bool slaveOk() const override {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
     bool adminOnly() const override {
diff --git a/src/mongo/db/s/config/configsvr_control_balancer_command.cpp b/src/mongo/db/s/config/configsvr_control_balancer_command.cpp
index 19b1fb0f263..1dc8c20f2c1 100644
--- a/src/mongo/db/s/config/configsvr_control_balancer_command.cpp
+++ b/src/mongo/db/s/config/configsvr_control_balancer_command.cpp
@@ -50,8 +50,8 @@ public:
                "directly. Controls the balancer state.";
     }
 
-    bool slaveOk() const override {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
     bool adminOnly() const override {
diff --git a/src/mongo/db/s/config/configsvr_create_database_command.cpp b/src/mongo/db/s/config/configsvr_create_database_command.cpp
index 556c6b5e0a2..797f76f5720 100644
--- a/src/mongo/db/s/config/configsvr_create_database_command.cpp
+++ b/src/mongo/db/s/config/configsvr_create_database_command.cpp
@@ -63,8 +63,8 @@ class ConfigSvrCreateDatabaseCommand : public BasicCommand {
 public:
     ConfigSvrCreateDatabaseCommand() : BasicCommand("_configsvrCreateDatabase") {}
 
-    virtual bool slaveOk() const {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
     virtual bool adminOnly() const {
diff --git a/src/mongo/db/s/config/configsvr_drop_collection_command.cpp b/src/mongo/db/s/config/configsvr_drop_collection_command.cpp
index 7bd0bdbd541..fd2c5ca9b93 100644
--- a/src/mongo/db/s/config/configsvr_drop_collection_command.cpp
+++ b/src/mongo/db/s/config/configsvr_drop_collection_command.cpp
@@ -60,8 +60,8 @@ class ConfigSvrDropCollectionCommand : public BasicCommand {
 public:
     ConfigSvrDropCollectionCommand() : BasicCommand("_configsvrDropCollection") {}
 
-    bool slaveOk() const override {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
     bool adminOnly() const override {
diff --git a/src/mongo/db/s/config/configsvr_drop_database_command.cpp b/src/mongo/db/s/config/configsvr_drop_database_command.cpp
index cef41aa0d57..8a9d35df9e8 100644
--- a/src/mongo/db/s/config/configsvr_drop_database_command.cpp
+++ b/src/mongo/db/s/config/configsvr_drop_database_command.cpp
@@ -54,8 +54,8 @@ class ConfigSvrDropDatabaseCommand : public BasicCommand {
 public:
     ConfigSvrDropDatabaseCommand() : BasicCommand("_configsvrDropDatabase") {}
 
-    bool slaveOk() const override {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
     bool adminOnly() const override {
diff --git a/src/mongo/db/s/config/configsvr_enable_sharding_command.cpp b/src/mongo/db/s/config/configsvr_enable_sharding_command.cpp
index 2cb4670595f..9bdbd5c5669 100644
--- a/src/mongo/db/s/config/configsvr_enable_sharding_command.cpp
+++ b/src/mongo/db/s/config/configsvr_enable_sharding_command.cpp
@@ -61,8 +61,8 @@ class ConfigSvrEnableShardingCommand : public BasicCommand {
 public:
     ConfigSvrEnableShardingCommand() : BasicCommand("_configsvrEnableSharding") {}
 
-    virtual bool slaveOk() const {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
     virtual bool adminOnly() const {
diff --git a/src/mongo/db/s/config/configsvr_merge_chunk_command.cpp b/src/mongo/db/s/config/configsvr_merge_chunk_command.cpp
index 3fb76ac3056..37c32c6781a 100644
--- a/src/mongo/db/s/config/configsvr_merge_chunk_command.cpp
+++ b/src/mongo/db/s/config/configsvr_merge_chunk_command.cpp
@@ -72,8 +72,8 @@ public:
                "not call directly. Receives, validates, and processes a MergeChunkRequest";
     }
 
-    bool slaveOk() const override {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
     bool adminOnly() const override {
diff --git a/src/mongo/db/s/config/configsvr_move_chunk_command.cpp b/src/mongo/db/s/config/configsvr_move_chunk_command.cpp
index 904185e754a..f64994fcfba 100644
--- a/src/mongo/db/s/config/configsvr_move_chunk_command.cpp
+++ b/src/mongo/db/s/config/configsvr_move_chunk_command.cpp
@@ -56,8 +56,8 @@ public:
                "directly. Requests the balancer to move or rebalance a single chunk.";
     }
 
-    bool slaveOk() const override {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
     bool adminOnly() const override {
diff --git a/src/mongo/db/s/config/configsvr_move_primary_command.cpp b/src/mongo/db/s/config/configsvr_move_primary_command.cpp
index 7f5b3a4169d..3ff60940242 100644
--- a/src/mongo/db/s/config/configsvr_move_primary_command.cpp
+++ b/src/mongo/db/s/config/configsvr_move_primary_command.cpp
@@ -68,8 +68,8 @@ class ConfigSvrMovePrimaryCommand : public BasicCommand {
 public:
     ConfigSvrMovePrimaryCommand() : BasicCommand("_configsvrMovePrimary") {}
 
-    virtual bool slaveOk() const {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
     virtual bool adminOnly() const {
diff --git a/src/mongo/db/s/config/configsvr_remove_shard_command.cpp b/src/mongo/db/s/config/configsvr_remove_shard_command.cpp
index e8d089c9370..d55e81b4ba9 100644
--- a/src/mongo/db/s/config/configsvr_remove_shard_command.cpp
+++ b/src/mongo/db/s/config/configsvr_remove_shard_command.cpp
@@ -62,8 +62,8 @@ public:
                "directly. Removes a shard from the cluster.";
     }
 
-    bool slaveOk() const override {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
     bool adminOnly() const override {
diff --git a/src/mongo/db/s/config/configsvr_remove_shard_from_zone_command.cpp b/src/mongo/db/s/config/configsvr_remove_shard_from_zone_command.cpp
index 7656550edff..9aa7f9285e2 100644
--- a/src/mongo/db/s/config/configsvr_remove_shard_from_zone_command.cpp
+++ b/src/mongo/db/s/config/configsvr_remove_shard_from_zone_command.cpp
@@ -65,8 +65,8 @@ public:
                "directly. Validates and removes the shard from the zone.";
     }
 
-    bool slaveOk() const override {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
     bool adminOnly() const override {
diff --git a/src/mongo/db/s/config/configsvr_shard_collection_command.cpp b/src/mongo/db/s/config/configsvr_shard_collection_command.cpp
index b602fed5350..63b6f00a48d 100644
--- a/src/mongo/db/s/config/configsvr_shard_collection_command.cpp
+++ b/src/mongo/db/s/config/configsvr_shard_collection_command.cpp
@@ -706,8 +706,8 @@ public:
         return Status::OK();
     }
 
-    bool slaveOk() const override {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
     bool adminOnly() const override {
diff --git a/src/mongo/db/s/config/configsvr_split_chunk_command.cpp b/src/mongo/db/s/config/configsvr_split_chunk_command.cpp
index b3f536871e5..4d66c7ffa8b 100644
--- a/src/mongo/db/s/config/configsvr_split_chunk_command.cpp
+++ b/src/mongo/db/s/config/configsvr_split_chunk_command.cpp
@@ -70,8 +70,8 @@ public:
                "not call directly. Receives, validates, and processes a SplitChunkRequest.";
     }
 
-    bool slaveOk() const override {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
     bool adminOnly() const override {
diff --git a/src/mongo/db/s/config/configsvr_update_zone_key_range_command.cpp b/src/mongo/db/s/config/configsvr_update_zone_key_range_command.cpp
index ed83028907d..1742699b038 100644
--- a/src/mongo/db/s/config/configsvr_update_zone_key_range_command.cpp
+++ b/src/mongo/db/s/config/configsvr_update_zone_key_range_command.cpp
@@ -67,8 +67,8 @@ public:
                "directly. Validates and assigns a new range to a zone.";
     }
 
-    bool slaveOk() const override {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
     bool adminOnly() const override {
diff --git a/src/mongo/db/s/flush_routing_table_cache_updates_command.cpp b/src/mongo/db/s/flush_routing_table_cache_updates_command.cpp
index 8c4732c1dea..36ea067ab63 100644
--- a/src/mongo/db/s/flush_routing_table_cache_updates_command.cpp
+++ b/src/mongo/db/s/flush_routing_table_cache_updates_command.cpp
@@ -70,8 +70,8 @@ public:
         return true;
     }
 
-    bool slaveOk() const override {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
     bool supportsWriteConcern(const BSONObj& cmd) const override {
diff --git a/src/mongo/db/s/get_shard_version_command.cpp b/src/mongo/db/s/get_shard_version_command.cpp
index 4ce02d070a6..2e580a669f8 100644
--- a/src/mongo/db/s/get_shard_version_command.cpp
+++ b/src/mongo/db/s/get_shard_version_command.cpp
@@ -58,8 +58,8 @@ public:
         return false;
     }
 
-    bool slaveOk() const override {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
     bool adminOnly() const override {
diff --git a/src/mongo/db/s/merge_chunks_command.cpp b/src/mongo/db/s/merge_chunks_command.cpp
index 5b7e68fda56..d7a355e5f95 100644
--- a/src/mongo/db/s/merge_chunks_command.cpp
+++ b/src/mongo/db/s/merge_chunks_command.cpp
@@ -333,8 +333,8 @@ public:
         return true;
     }
 
-    bool slaveOk() const override {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
     bool supportsWriteConcern(const BSONObj& cmd) const override {
diff --git a/src/mongo/db/s/migration_chunk_cloner_source_legacy_commands.cpp b/src/mongo/db/s/migration_chunk_cloner_source_legacy_commands.cpp
index 785a3309d22..a6f9b86e501 100644
--- a/src/mongo/db/s/migration_chunk_cloner_source_legacy_commands.cpp
+++ b/src/mongo/db/s/migration_chunk_cloner_source_legacy_commands.cpp
@@ -125,8 +125,8 @@ public:
         return false;
     }
 
-    virtual bool slaveOk() const {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
     virtual bool adminOnly() const {
@@ -187,8 +187,8 @@ public:
         return false;
     }
 
-    virtual bool slaveOk() const {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
     virtual bool adminOnly() const {
@@ -236,8 +236,8 @@ public:
         return false;
     }
 
-    virtual bool slaveOk() const {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
     virtual bool adminOnly() const {
diff --git a/src/mongo/db/s/migration_destination_manager_legacy_commands.cpp b/src/mongo/db/s/migration_destination_manager_legacy_commands.cpp
index d4b235f251f..36122f38c4f 100644
--- a/src/mongo/db/s/migration_destination_manager_legacy_commands.cpp
+++ b/src/mongo/db/s/migration_destination_manager_legacy_commands.cpp
@@ -63,8 +63,8 @@ public:
         return "internal";
     }
 
-    virtual bool slaveOk() const {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
     virtual bool adminOnly() const {
@@ -163,8 +163,8 @@ public:
         return "internal";
     }
 
-    virtual bool slaveOk() const {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
     virtual bool adminOnly() const {
@@ -201,8 +201,8 @@ public:
         return "internal";
     }
 
-    virtual bool slaveOk() const {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
     virtual bool adminOnly() const {
@@ -247,8 +247,8 @@ public:
         return "internal";
     }
 
-    virtual bool slaveOk() const {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
     virtual bool adminOnly() const {
diff --git a/src/mongo/db/s/move_chunk_command.cpp b/src/mongo/db/s/move_chunk_command.cpp
index 5233290efc2..e1cb32cf925 100644
--- a/src/mongo/db/s/move_chunk_command.cpp
+++ b/src/mongo/db/s/move_chunk_command.cpp
@@ -80,8 +80,8 @@ public:
         return "should not be calling this directly";
     }
 
-    bool slaveOk() const override {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
     bool adminOnly() const override {
diff --git a/src/mongo/db/s/set_shard_version_command.cpp b/src/mongo/db/s/set_shard_version_command.cpp
index 7ddd6d2f6a1..1e4f734b16c 100644
--- a/src/mongo/db/s/set_shard_version_command.cpp
+++ b/src/mongo/db/s/set_shard_version_command.cpp
@@ -70,8 +70,8 @@ public:
         return true;
     }
 
-    bool slaveOk() const override {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
 
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
diff --git a/src/mongo/db/s/sharding_state_command.cpp b/src/mongo/db/s/sharding_state_command.cpp
index 0e3aea8b652..6fc0887021a 100644
--- a/src/mongo/db/s/sharding_state_command.cpp
+++ b/src/mongo/db/s/sharding_state_command.cpp
@@ -48,8 +48,8 @@ public:
         return false;
     }
 
-    bool slaveOk() const override {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
 
     bool adminOnly() const override {
diff --git a/src/mongo/db/s/split_chunk_command.cpp b/src/mongo/db/s/split_chunk_command.cpp
index 8de8e6dc966..3c61c3b1498 100644
--- a/src/mongo/db/s/split_chunk_command.cpp
+++ b/src/mongo/db/s/split_chunk_command.cpp
@@ -68,8 +68,8 @@ public:
         return false;
     }
 
-    bool slaveOk() const override {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
     bool adminOnly() const override {
diff --git a/src/mongo/db/s/split_vector_command.cpp b/src/mongo/db/s/split_vector_command.cpp
index 4ac78111bf7..2ee8ad88d7c 100644
--- a/src/mongo/db/s/split_vector_command.cpp
+++ b/src/mongo/db/s/split_vector_command.cpp
@@ -49,8 +49,8 @@ public:
         return false;
     }
 
-    bool slaveOk() const override {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
     std::string help() const override {
diff --git a/src/mongo/db/s/unset_sharding_command.cpp b/src/mongo/db/s/unset_sharding_command.cpp
index 5aae6e00a94..a6e6e61d970 100644
--- a/src/mongo/db/s/unset_sharding_command.cpp
+++ b/src/mongo/db/s/unset_sharding_command.cpp
@@ -60,8 +60,8 @@ public:
         return true;
     }
 
-    bool slaveOk() const override {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
 
     void addRequiredPrivileges(const std::string& dbname,
diff --git a/src/mongo/db/service_entry_point_mongod.cpp b/src/mongo/db/service_entry_point_mongod.cpp
index 1d6d69d257b..2b27ec8b22c 100644
--- a/src/mongo/db/service_entry_point_mongod.cpp
+++ b/src/mongo/db/service_entry_point_mongod.cpp
@@ -37,6 +37,7 @@
 #include "mongo/db/auth/authorization_session.h"
 #include "mongo/db/auth/impersonation_session.h"
 #include "mongo/db/client.h"
+#include "mongo/db/command_can_run_here.h"
 #include "mongo/db/commands.h"
 #include "mongo/db/commands/fsync.h"
 #include "mongo/db/concurrency/global_lock_acquisition_tracker.h"
@@ -609,18 +610,13 @@ void execCommandDatabase(OperationContext* opCtx,
 
         if (!opCtx->getClient()->isInDirectClient() &&
             !MONGO_FAIL_POINT(skipCheckingForNotMasterInCommandDispatch)) {
-
-            bool commandCanRunOnSecondary = command->slaveOk();
-
-            bool commandIsOverriddenToRunOnSecondary =
-                command->slaveOverrideOk() && ReadPreferenceSetting::get(opCtx).canRunOnSecondary();
-
-            bool iAmStandalone = !opCtx->writesAreReplicated();
-            bool canRunHere = iAmPrimary || commandCanRunOnSecondary ||
-                commandIsOverriddenToRunOnSecondary || iAmStandalone;
-
-            // This logic is clearer if we don't have to invert it.
-            if (!canRunHere && command->slaveOverrideOk()) {
+            auto allowed = command->secondaryAllowed();
+            bool alwaysAllowed = allowed == Command::AllowedOnSecondary::kAlways;
+            bool couldHaveOptedIn = allowed == Command::AllowedOnSecondary::kOptIn;
+            bool optedIn =
+                couldHaveOptedIn && ReadPreferenceSetting::get(opCtx).canRunOnSecondary();
+            bool canRunHere = commandCanRunHere(opCtx, dbname, command);
+            if (!canRunHere && couldHaveOptedIn) {
                 uasserted(ErrorCodes::NotMasterNoSlaveOk, "not master and slaveOk=false");
             }
 
@@ -644,7 +640,7 @@ void execCommandDatabase(OperationContext* opCtx,
                 // Check ticket SERVER-21432, slaveOk commands are allowed in drain mode
                 uassert(ErrorCodes::NotMasterOrSecondary,
                         "node is in drain mode",
-                        commandIsOverriddenToRunOnSecondary || commandCanRunOnSecondary);
+                        optedIn || alwaysAllowed);
             }
         }
 
diff --git a/src/mongo/db/storage/mmap_v1/journal_latency_test_cmd.cpp b/src/mongo/db/storage/mmap_v1/journal_latency_test_cmd.cpp
index 4f90ba1c6d0..b8707efd3d1 100644
--- a/src/mongo/db/storage/mmap_v1/journal_latency_test_cmd.cpp
+++ b/src/mongo/db/storage/mmap_v1/journal_latency_test_cmd.cpp
@@ -68,8 +68,8 @@ class JournalLatencyTestCmd : public BasicCommand {
 public:
     JournalLatencyTestCmd() : BasicCommand("journalLatencyTest") {}
 
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
         return false;
diff --git a/src/mongo/s/client/shard_connection.cpp b/src/mongo/s/client/shard_connection.cpp
index d79611871e4..fcb033b1025 100644
--- a/src/mongo/s/client/shard_connection.cpp
+++ b/src/mongo/s/client/shard_connection.cpp
@@ -98,8 +98,8 @@ public:
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
         return false;
     }
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
 
     // Same privs as connPoolStats
diff --git a/src/mongo/s/commands/cluster_add_shard_cmd.cpp b/src/mongo/s/commands/cluster_add_shard_cmd.cpp
index 56cdf9650ab..df13a652f37 100644
--- a/src/mongo/s/commands/cluster_add_shard_cmd.cpp
+++ b/src/mongo/s/commands/cluster_add_shard_cmd.cpp
@@ -56,8 +56,8 @@ class AddShardCmd : public BasicCommand {
 public:
     AddShardCmd() : BasicCommand("addShard", "addshard") {}
 
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
 
     virtual bool adminOnly() const {
diff --git a/src/mongo/s/commands/cluster_add_shard_to_zone_cmd.cpp b/src/mongo/s/commands/cluster_add_shard_to_zone_cmd.cpp
index e82e6bc0817..419ca7e2a0e 100644
--- a/src/mongo/s/commands/cluster_add_shard_to_zone_cmd.cpp
+++ b/src/mongo/s/commands/cluster_add_shard_to_zone_cmd.cpp
@@ -69,8 +69,8 @@ class AddShardToZoneCmd : public BasicCommand {
 public:
     AddShardToZoneCmd() : BasicCommand("addShardToZone", "addshardtozone") {}
 
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
 
     virtual bool adminOnly() const {
diff --git a/src/mongo/s/commands/cluster_available_query_options_cmd.cpp b/src/mongo/s/commands/cluster_available_query_options_cmd.cpp
index d209c2ace34..8eccb031358 100644
--- a/src/mongo/s/commands/cluster_available_query_options_cmd.cpp
+++ b/src/mongo/s/commands/cluster_available_query_options_cmd.cpp
@@ -39,8 +39,8 @@ class AvailableQueryOptions : public BasicCommand {
 public:
     AvailableQueryOptions() : BasicCommand("availableQueryOptions", "availablequeryoptions") {}
 
-    bool slaveOk() const override {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
 
     bool supportsWriteConcern(const BSONObj& cmd) const override {
diff --git a/src/mongo/s/commands/cluster_compact_cmd.cpp b/src/mongo/s/commands/cluster_compact_cmd.cpp
index 3d933804c49..d5fd03ae39a 100644
--- a/src/mongo/s/commands/cluster_compact_cmd.cpp
+++ b/src/mongo/s/commands/cluster_compact_cmd.cpp
@@ -37,8 +37,8 @@ class CompactCmd : public BasicCommand {
 public:
     CompactCmd() : BasicCommand("compact") {}
 
-    bool slaveOk() const override {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
 
     bool adminOnly() const override {
diff --git a/src/mongo/s/commands/cluster_control_balancer_cmd.cpp b/src/mongo/s/commands/cluster_control_balancer_cmd.cpp
index 11e05a559d0..5a60b6bb8d8 100644
--- a/src/mongo/s/commands/cluster_control_balancer_cmd.cpp
+++ b/src/mongo/s/commands/cluster_control_balancer_cmd.cpp
@@ -50,8 +50,8 @@ public:
           _configsvrCommandName(configsvrCommandName),
           _authorizationAction(authorizationAction) {}
 
-    bool slaveOk() const override {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
     bool adminOnly() const override {
diff --git a/src/mongo/s/commands/cluster_count_cmd.cpp b/src/mongo/s/commands/cluster_count_cmd.cpp
index f05f349982c..2c407b61005 100644
--- a/src/mongo/s/commands/cluster_count_cmd.cpp
+++ b/src/mongo/s/commands/cluster_count_cmd.cpp
@@ -51,8 +51,8 @@ class ClusterCountCmd : public ErrmsgCommandDeprecated {
 public:
     ClusterCountCmd() : ErrmsgCommandDeprecated("count") {}
 
-    bool slaveOk() const override {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
 
     bool adminOnly() const override {
diff --git a/src/mongo/s/commands/cluster_db_stats_cmd.cpp b/src/mongo/s/commands/cluster_db_stats_cmd.cpp
index 1d74af4d1e7..35a24f7d81d 100644
--- a/src/mongo/s/commands/cluster_db_stats_cmd.cpp
+++ b/src/mongo/s/commands/cluster_db_stats_cmd.cpp
@@ -44,8 +44,8 @@ class DBStatsCmd : public ErrmsgCommandDeprecated {
 public:
     DBStatsCmd() : ErrmsgCommandDeprecated("dbStats", "dbstats") {}
 
-    bool slaveOk() const override {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
     bool adminOnly() const override {
         return false;
diff --git a/src/mongo/s/commands/cluster_drop_cmd.cpp b/src/mongo/s/commands/cluster_drop_cmd.cpp
index 6a8081c20c2..a77abe079a6 100644
--- a/src/mongo/s/commands/cluster_drop_cmd.cpp
+++ b/src/mongo/s/commands/cluster_drop_cmd.cpp
@@ -45,8 +45,8 @@ class DropCmd : public BasicCommand {
 public:
     DropCmd() : BasicCommand("drop") {}
 
-    bool slaveOk() const override {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
 
     bool adminOnly() const override {
diff --git a/src/mongo/s/commands/cluster_drop_database_cmd.cpp b/src/mongo/s/commands/cluster_drop_database_cmd.cpp
index da0380565eb..207db3d3c0d 100644
--- a/src/mongo/s/commands/cluster_drop_database_cmd.cpp
+++ b/src/mongo/s/commands/cluster_drop_database_cmd.cpp
@@ -46,8 +46,8 @@ class DropDatabaseCmd : public BasicCommand {
 public:
     DropDatabaseCmd() : BasicCommand("dropDatabase") {}
 
-    bool slaveOk() const override {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
 
     bool adminOnly() const override {
diff --git a/src/mongo/s/commands/cluster_enable_sharding_cmd.cpp b/src/mongo/s/commands/cluster_enable_sharding_cmd.cpp
index 77bdbbb6681..1869632ef68 100644
--- a/src/mongo/s/commands/cluster_enable_sharding_cmd.cpp
+++ b/src/mongo/s/commands/cluster_enable_sharding_cmd.cpp
@@ -52,8 +52,8 @@ class EnableShardingCmd : public ErrmsgCommandDeprecated {
 public:
     EnableShardingCmd() : ErrmsgCommandDeprecated("enableSharding", "enablesharding") {}
 
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
 
     virtual bool adminOnly() const {
diff --git a/src/mongo/s/commands/cluster_explain_cmd.cpp b/src/mongo/s/commands/cluster_explain_cmd.cpp
index b734501ab36..3f435329d75 100644
--- a/src/mongo/s/commands/cluster_explain_cmd.cpp
+++ b/src/mongo/s/commands/cluster_explain_cmd.cpp
@@ -61,12 +61,8 @@ public:
     /**
      * Running an explain on a secondary requires explicitly setting slaveOk.
      */
-    virtual bool slaveOk() const {
-        return false;
-    }
-
-    virtual bool slaveOverrideOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kOptIn;
     }
 
     virtual bool maintenanceOk() const {
diff --git a/src/mongo/s/commands/cluster_find_and_modify_cmd.cpp b/src/mongo/s/commands/cluster_find_and_modify_cmd.cpp
index 90b5665e6a0..922d271e870 100644
--- a/src/mongo/s/commands/cluster_find_and_modify_cmd.cpp
+++ b/src/mongo/s/commands/cluster_find_and_modify_cmd.cpp
@@ -78,8 +78,8 @@ class FindAndModifyCmd : public BasicCommand {
 public:
     FindAndModifyCmd() : BasicCommand("findAndModify", "findandmodify") {}
 
-    bool slaveOk() const override {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
 
     bool adminOnly() const override {
diff --git a/src/mongo/s/commands/cluster_find_cmd.cpp b/src/mongo/s/commands/cluster_find_cmd.cpp
index 9c8adb1a64b..8b53c5b6f6b 100644
--- a/src/mongo/s/commands/cluster_find_cmd.cpp
+++ b/src/mongo/s/commands/cluster_find_cmd.cpp
@@ -65,12 +65,8 @@ public:
         return false;
     }
 
-    bool slaveOk() const final {
-        return false;
-    }
-
-    bool slaveOverrideOk() const final {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kOptIn;
     }
 
     bool maintenanceOk() const final {
diff --git a/src/mongo/s/commands/cluster_flush_router_config_cmd.cpp b/src/mongo/s/commands/cluster_flush_router_config_cmd.cpp
index 61f0f9d640a..2b76f374342 100644
--- a/src/mongo/s/commands/cluster_flush_router_config_cmd.cpp
+++ b/src/mongo/s/commands/cluster_flush_router_config_cmd.cpp
@@ -39,8 +39,8 @@ class FlushRouterConfigCmd : public BasicCommand {
 public:
     FlushRouterConfigCmd() : BasicCommand("flushRouterConfig", "flushrouterconfig") {}
 
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
 
     virtual bool adminOnly() const {
diff --git a/src/mongo/s/commands/cluster_fsync_cmd.cpp b/src/mongo/s/commands/cluster_fsync_cmd.cpp
index fa6363ed9fb..3f578bc9ddb 100644
--- a/src/mongo/s/commands/cluster_fsync_cmd.cpp
+++ b/src/mongo/s/commands/cluster_fsync_cmd.cpp
@@ -42,8 +42,8 @@ class FsyncCommand : public ErrmsgCommandDeprecated {
 public:
     FsyncCommand() : ErrmsgCommandDeprecated("fsync") {}
 
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
 
     virtual bool adminOnly() const {
diff --git a/src/mongo/s/commands/cluster_ftdc_commands.cpp b/src/mongo/s/commands/cluster_ftdc_commands.cpp
index c6c30cebf95..6942bec0bdb 100644
--- a/src/mongo/s/commands/cluster_ftdc_commands.cpp
+++ b/src/mongo/s/commands/cluster_ftdc_commands.cpp
@@ -56,8 +56,8 @@ public:
         return "get latest diagnostic data collection snapshot";
     }
 
-    bool slaveOk() const override {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
 
     bool supportsWriteConcern(const BSONObj& cmd) const override {
diff --git a/src/mongo/s/commands/cluster_get_last_error_cmd.cpp b/src/mongo/s/commands/cluster_get_last_error_cmd.cpp
index 9665072154d..3134fbb22c3 100644
--- a/src/mongo/s/commands/cluster_get_last_error_cmd.cpp
+++ b/src/mongo/s/commands/cluster_get_last_error_cmd.cpp
@@ -195,8 +195,8 @@ public:
         return false;
     }
 
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
 
     std::string help() const override {
diff --git a/src/mongo/s/commands/cluster_get_prev_error_cmd.cpp b/src/mongo/s/commands/cluster_get_prev_error_cmd.cpp
index 399eccc6684..d36e91916b8 100644
--- a/src/mongo/s/commands/cluster_get_prev_error_cmd.cpp
+++ b/src/mongo/s/commands/cluster_get_prev_error_cmd.cpp
@@ -47,8 +47,8 @@ public:
         return false;
     }
 
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
 
     std::string help() const override {
diff --git a/src/mongo/s/commands/cluster_get_shard_map_cmd.cpp b/src/mongo/s/commands/cluster_get_shard_map_cmd.cpp
index 3b70cf27d94..6672c597a39 100644
--- a/src/mongo/s/commands/cluster_get_shard_map_cmd.cpp
+++ b/src/mongo/s/commands/cluster_get_shard_map_cmd.cpp
@@ -47,8 +47,8 @@ public:
         return false;
     }
 
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
 
     std::string help() const override {
diff --git a/src/mongo/s/commands/cluster_get_shard_version_cmd.cpp b/src/mongo/s/commands/cluster_get_shard_version_cmd.cpp
index c55c77ef3f8..05f04d9249a 100644
--- a/src/mongo/s/commands/cluster_get_shard_version_cmd.cpp
+++ b/src/mongo/s/commands/cluster_get_shard_version_cmd.cpp
@@ -47,8 +47,8 @@ class GetShardVersion : public BasicCommand {
 public:
     GetShardVersion() : BasicCommand("getShardVersion", "getshardversion") {}
 
-    bool slaveOk() const override {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
 
     bool adminOnly() const override {
diff --git a/src/mongo/s/commands/cluster_getmore_cmd.cpp b/src/mongo/s/commands/cluster_getmore_cmd.cpp
index 00784d5c55c..4274efb7089 100644
--- a/src/mongo/s/commands/cluster_getmore_cmd.cpp
+++ b/src/mongo/s/commands/cluster_getmore_cmd.cpp
@@ -55,8 +55,8 @@ public:
         return false;
     }
 
-    bool slaveOk() const final {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const final {
+        return AllowedOnSecondary::kAlways;
     }
 
     bool maintenanceOk() const final {
diff --git a/src/mongo/s/commands/cluster_index_filter_cmd.cpp b/src/mongo/s/commands/cluster_index_filter_cmd.cpp
index c06c42f2ce0..ba61748779f 100644
--- a/src/mongo/s/commands/cluster_index_filter_cmd.cpp
+++ b/src/mongo/s/commands/cluster_index_filter_cmd.cpp
@@ -61,15 +61,10 @@ public:
 
     virtual ~ClusterIndexFilterCmd() {}
 
-    bool slaveOk() const {
-        return false;
-    }
-
-    bool slaveOverrideOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kOptIn;
     }
 
-
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
         return false;
     }
diff --git a/src/mongo/s/commands/cluster_is_db_grid_cmd.cpp b/src/mongo/s/commands/cluster_is_db_grid_cmd.cpp
index 3304202e4a7..297e4403c2f 100644
--- a/src/mongo/s/commands/cluster_is_db_grid_cmd.cpp
+++ b/src/mongo/s/commands/cluster_is_db_grid_cmd.cpp
@@ -43,8 +43,8 @@ public:
         return false;
     }
 
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
 
     virtual void addRequiredPrivileges(const std::string& dbname,
diff --git a/src/mongo/s/commands/cluster_is_master_cmd.cpp b/src/mongo/s/commands/cluster_is_master_cmd.cpp
index 8caf0cde2c4..220d97e9e36 100644
--- a/src/mongo/s/commands/cluster_is_master_cmd.cpp
+++ b/src/mongo/s/commands/cluster_is_master_cmd.cpp
@@ -53,8 +53,8 @@ public:
         return false;
     }
 
-    bool slaveOk() const override {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
 
     std::string help() const override {
diff --git a/src/mongo/s/commands/cluster_kill_op.cpp b/src/mongo/s/commands/cluster_kill_op.cpp
index bfeb02ea493..3418d4049be 100644
--- a/src/mongo/s/commands/cluster_kill_op.cpp
+++ b/src/mongo/s/commands/cluster_kill_op.cpp
@@ -60,8 +60,8 @@ public:
         return false;
     }
 
-    bool slaveOk() const final {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const final {
+        return AllowedOnSecondary::kAlways;
     }
 
     bool adminOnly() const final {
diff --git a/src/mongo/s/commands/cluster_list_databases_cmd.cpp b/src/mongo/s/commands/cluster_list_databases_cmd.cpp
index 5a6d8a16552..064b89d3ca4 100644
--- a/src/mongo/s/commands/cluster_list_databases_cmd.cpp
+++ b/src/mongo/s/commands/cluster_list_databases_cmd.cpp
@@ -56,12 +56,8 @@ class ListDatabasesCmd : public BasicCommand {
 public:
     ListDatabasesCmd() : BasicCommand("listDatabases", "listdatabases") {}
 
-    bool slaveOk() const final {
-        return true;
-    }
-
-    bool slaveOverrideOk() const final {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const final {
+        return AllowedOnSecondary::kAlways;
     }
 
     bool adminOnly() const final {
diff --git a/src/mongo/s/commands/cluster_list_shards_cmd.cpp b/src/mongo/s/commands/cluster_list_shards_cmd.cpp
index 309c45a3be2..59ceb90f106 100644
--- a/src/mongo/s/commands/cluster_list_shards_cmd.cpp
+++ b/src/mongo/s/commands/cluster_list_shards_cmd.cpp
@@ -50,8 +50,8 @@ public:
         return true;
     }
 
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
 
     bool supportsWriteConcern(const BSONObj& cmd) const override {
diff --git a/src/mongo/s/commands/cluster_map_reduce_cmd.cpp b/src/mongo/s/commands/cluster_map_reduce_cmd.cpp
index 8787beefc09..5e58c1c0e68 100644
--- a/src/mongo/s/commands/cluster_map_reduce_cmd.cpp
+++ b/src/mongo/s/commands/cluster_map_reduce_cmd.cpp
@@ -151,8 +151,8 @@ class MRCmd : public ErrmsgCommandDeprecated {
 public:
     MRCmd() : ErrmsgCommandDeprecated("mapReduce", "mapreduce") {}
 
-    bool slaveOk() const override {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
 
     bool adminOnly() const override {
diff --git a/src/mongo/s/commands/cluster_merge_chunks_cmd.cpp b/src/mongo/s/commands/cluster_merge_chunks_cmd.cpp
index abfe8fe2f08..ecdfa931cd4 100644
--- a/src/mongo/s/commands/cluster_merge_chunks_cmd.cpp
+++ b/src/mongo/s/commands/cluster_merge_chunks_cmd.cpp
@@ -80,8 +80,8 @@ public:
         return true;
     }
 
-    bool slaveOk() const override {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
     bool supportsWriteConcern(const BSONObj& cmd) const override {
diff --git a/src/mongo/s/commands/cluster_move_chunk_cmd.cpp b/src/mongo/s/commands/cluster_move_chunk_cmd.cpp
index d1a3ef74e84..e251376c920 100644
--- a/src/mongo/s/commands/cluster_move_chunk_cmd.cpp
+++ b/src/mongo/s/commands/cluster_move_chunk_cmd.cpp
@@ -55,10 +55,9 @@ class MoveChunkCmd : public ErrmsgCommandDeprecated {
 public:
     MoveChunkCmd() : ErrmsgCommandDeprecated("moveChunk", "movechunk") {}
 
-    bool slaveOk() const override {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
-
     bool adminOnly() const override {
         return true;
     }
diff --git a/src/mongo/s/commands/cluster_move_primary_cmd.cpp b/src/mongo/s/commands/cluster_move_primary_cmd.cpp
index 181c3a3b8fd..34540a60b69 100644
--- a/src/mongo/s/commands/cluster_move_primary_cmd.cpp
+++ b/src/mongo/s/commands/cluster_move_primary_cmd.cpp
@@ -57,8 +57,8 @@ class MoveDatabasePrimaryCommand : public BasicCommand {
 public:
     MoveDatabasePrimaryCommand() : BasicCommand("movePrimary", "moveprimary") {}
 
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
 
     virtual bool adminOnly() const {
diff --git a/src/mongo/s/commands/cluster_multicast.cpp b/src/mongo/s/commands/cluster_multicast.cpp
index d0d8d11c607..b26bdbe4e88 100644
--- a/src/mongo/s/commands/cluster_multicast.cpp
+++ b/src/mongo/s/commands/cluster_multicast.cpp
@@ -66,10 +66,9 @@ class MulticastCmd : public BasicCommand {
 public:
     MulticastCmd() : BasicCommand("multicast") {}
 
-    bool slaveOk() const override {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
-
     bool adminOnly() const override {
         return true;
     }
diff --git a/src/mongo/s/commands/cluster_netstat_cmd.cpp b/src/mongo/s/commands/cluster_netstat_cmd.cpp
index b8ffa72b530..5dd1e0b1a1a 100644
--- a/src/mongo/s/commands/cluster_netstat_cmd.cpp
+++ b/src/mongo/s/commands/cluster_netstat_cmd.cpp
@@ -40,8 +40,8 @@ class NetStatCmd : public BasicCommand {
 public:
     NetStatCmd() : BasicCommand("netstat") {}
 
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
 
     virtual bool adminOnly() const {
diff --git a/src/mongo/s/commands/cluster_pipeline_cmd.cpp b/src/mongo/s/commands/cluster_pipeline_cmd.cpp
index f9d972d4771..5983c0aa9c6 100644
--- a/src/mongo/s/commands/cluster_pipeline_cmd.cpp
+++ b/src/mongo/s/commands/cluster_pipeline_cmd.cpp
@@ -47,8 +47,8 @@ public:
                "http://dochub.mongodb.org/core/aggregation for more details.";
     }
 
-    bool slaveOk() const override {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
 
     bool adminOnly() const override {
diff --git a/src/mongo/s/commands/cluster_plan_cache_cmd.cpp b/src/mongo/s/commands/cluster_plan_cache_cmd.cpp
index 2e1b63653cd..8fa4c1edfc2 100644
--- a/src/mongo/s/commands/cluster_plan_cache_cmd.cpp
+++ b/src/mongo/s/commands/cluster_plan_cache_cmd.cpp
@@ -54,12 +54,8 @@ class ClusterPlanCacheCmd : public BasicCommand {
 public:
     virtual ~ClusterPlanCacheCmd() {}
 
-    bool slaveOk() const {
-        return false;
-    }
-
-    bool slaveOverrideOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kOptIn;
     }
 
     bool supportsWriteConcern(const BSONObj& cmd) const override {
diff --git a/src/mongo/s/commands/cluster_profile_cmd.cpp b/src/mongo/s/commands/cluster_profile_cmd.cpp
index cab007638d9..5129922d3a5 100644
--- a/src/mongo/s/commands/cluster_profile_cmd.cpp
+++ b/src/mongo/s/commands/cluster_profile_cmd.cpp
@@ -37,8 +37,8 @@ class ProfileCmd : public ErrmsgCommandDeprecated {
 public:
     ProfileCmd() : ErrmsgCommandDeprecated("profile") {}
 
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
 
     virtual bool adminOnly() const {
diff --git a/src/mongo/s/commands/cluster_remove_shard_cmd.cpp b/src/mongo/s/commands/cluster_remove_shard_cmd.cpp
index 51d863cc668..336f51d0437 100644
--- a/src/mongo/s/commands/cluster_remove_shard_cmd.cpp
+++ b/src/mongo/s/commands/cluster_remove_shard_cmd.cpp
@@ -49,8 +49,8 @@ public:
         return "remove a shard from the system.";
     }
 
-    bool slaveOk() const override {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
     bool adminOnly() const override {
diff --git a/src/mongo/s/commands/cluster_remove_shard_from_zone_cmd.cpp b/src/mongo/s/commands/cluster_remove_shard_from_zone_cmd.cpp
index 0118f75ee14..bc35d3c573c 100644
--- a/src/mongo/s/commands/cluster_remove_shard_from_zone_cmd.cpp
+++ b/src/mongo/s/commands/cluster_remove_shard_from_zone_cmd.cpp
@@ -69,8 +69,8 @@ class RemoveShardFromZoneCmd : public BasicCommand {
 public:
     RemoveShardFromZoneCmd() : BasicCommand("removeShardFromZone", "removeshardfromzone") {}
 
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
 
     virtual bool adminOnly() const {
diff --git a/src/mongo/s/commands/cluster_repl_set_get_status_cmd.cpp b/src/mongo/s/commands/cluster_repl_set_get_status_cmd.cpp
index 913d7248d11..0c70fdac88c 100644
--- a/src/mongo/s/commands/cluster_repl_set_get_status_cmd.cpp
+++ b/src/mongo/s/commands/cluster_repl_set_get_status_cmd.cpp
@@ -40,8 +40,8 @@ class CmdReplSetGetStatus : public ErrmsgCommandDeprecated {
 public:
     CmdReplSetGetStatus() : ErrmsgCommandDeprecated("replSetGetStatus") {}
 
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
 
     virtual bool adminOnly() const {
diff --git a/src/mongo/s/commands/cluster_reset_error_cmd.cpp b/src/mongo/s/commands/cluster_reset_error_cmd.cpp
index 50ba801ba37..6df637aaf76 100644
--- a/src/mongo/s/commands/cluster_reset_error_cmd.cpp
+++ b/src/mongo/s/commands/cluster_reset_error_cmd.cpp
@@ -49,8 +49,8 @@ public:
         return false;
     }
 
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
 
     virtual void addRequiredPrivileges(const std::string& dbname,
diff --git a/src/mongo/s/commands/cluster_set_feature_compatibility_version_cmd.cpp b/src/mongo/s/commands/cluster_set_feature_compatibility_version_cmd.cpp
index 04502b0e214..2e519bc73f9 100644
--- a/src/mongo/s/commands/cluster_set_feature_compatibility_version_cmd.cpp
+++ b/src/mongo/s/commands/cluster_set_feature_compatibility_version_cmd.cpp
@@ -55,8 +55,8 @@ class SetFeatureCompatibilityVersionCmd : public BasicCommand {
 public:
     SetFeatureCompatibilityVersionCmd() : BasicCommand("setFeatureCompatibilityVersion") {}
 
-    virtual bool slaveOk() const {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
     virtual bool adminOnly() const {
diff --git a/src/mongo/s/commands/cluster_shard_collection_cmd.cpp b/src/mongo/s/commands/cluster_shard_collection_cmd.cpp
index 31d230f117f..f9fc5442099 100644
--- a/src/mongo/s/commands/cluster_shard_collection_cmd.cpp
+++ b/src/mongo/s/commands/cluster_shard_collection_cmd.cpp
@@ -70,8 +70,8 @@ class ShardCollectionCmd : public BasicCommand {
 public:
     ShardCollectionCmd() : BasicCommand("shardCollection", "shardcollection") {}
 
-    bool slaveOk() const override {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
 
     bool adminOnly() const override {
diff --git a/src/mongo/s/commands/cluster_split_cmd.cpp b/src/mongo/s/commands/cluster_split_cmd.cpp
index 1b709cf9f95..ec5fbe58d37 100644
--- a/src/mongo/s/commands/cluster_split_cmd.cpp
+++ b/src/mongo/s/commands/cluster_split_cmd.cpp
@@ -88,8 +88,8 @@ class SplitCollectionCmd : public ErrmsgCommandDeprecated {
 public:
     SplitCollectionCmd() : ErrmsgCommandDeprecated("split") {}
 
-    bool slaveOk() const override {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
 
     bool adminOnly() const override {
diff --git a/src/mongo/s/commands/cluster_update_zone_key_range_cmd.cpp b/src/mongo/s/commands/cluster_update_zone_key_range_cmd.cpp
index 0abb42b3a22..f286abc6a6b 100644
--- a/src/mongo/s/commands/cluster_update_zone_key_range_cmd.cpp
+++ b/src/mongo/s/commands/cluster_update_zone_key_range_cmd.cpp
@@ -72,8 +72,8 @@ class UpdateZoneKeyRangeCmd : public BasicCommand {
 public:
     UpdateZoneKeyRangeCmd() : BasicCommand("updateZoneKeyRange", "updatezonekeyRange") {}
 
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
 
     virtual bool adminOnly() const {
diff --git a/src/mongo/s/commands/cluster_user_management_commands.cpp b/src/mongo/s/commands/cluster_user_management_commands.cpp
index a9d6230b8cc..f908b1e98e1 100644
--- a/src/mongo/s/commands/cluster_user_management_commands.cpp
+++ b/src/mongo/s/commands/cluster_user_management_commands.cpp
@@ -67,11 +67,10 @@ class CmdCreateUser : public BasicCommand {
 public:
     CmdCreateUser() : BasicCommand("createUser") {}
 
-    virtual bool slaveOk() const {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
-
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
         return true;
     }
@@ -108,11 +107,10 @@ class CmdUpdateUser : public BasicCommand {
 public:
     CmdUpdateUser() : BasicCommand("updateUser") {}
 
-    virtual bool slaveOk() const {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
-
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
         return true;
     }
@@ -160,8 +158,8 @@ class CmdDropUser : public BasicCommand {
 public:
     CmdDropUser() : BasicCommand("dropUser") {}
 
-    virtual bool slaveOk() const {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
 
@@ -208,11 +206,10 @@ class CmdDropAllUsersFromDatabase : public BasicCommand {
 public:
     CmdDropAllUsersFromDatabase() : BasicCommand("dropAllUsersFromDatabase") {}
 
-    virtual bool slaveOk() const {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
-
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
         return true;
     }
@@ -251,8 +248,8 @@ class CmdGrantRolesToUser : public BasicCommand {
 public:
     CmdGrantRolesToUser() : BasicCommand("grantRolesToUser") {}
 
-    virtual bool slaveOk() const {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
 
@@ -301,8 +298,8 @@ class CmdRevokeRolesFromUser : public BasicCommand {
 public:
     CmdRevokeRolesFromUser() : BasicCommand("revokeRolesFromUser") {}
 
-    virtual bool slaveOk() const {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
 
@@ -349,15 +346,10 @@ public:
 
 class CmdUsersInfo : public BasicCommand {
 public:
-    virtual bool slaveOk() const {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kOptIn;
     }
 
-    virtual bool slaveOverrideOk() const {
-        return true;
-    }
-
-
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
         return false;
     }
@@ -388,11 +380,10 @@ class CmdCreateRole : public BasicCommand {
 public:
     CmdCreateRole() : BasicCommand("createRole") {}
 
-    virtual bool slaveOk() const {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
-
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
         return true;
     }
@@ -425,11 +416,10 @@ class CmdUpdateRole : public BasicCommand {
 public:
     CmdUpdateRole() : BasicCommand("updateRole") {}
 
-    virtual bool slaveOk() const {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
-
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
         return true;
     }
@@ -468,8 +458,8 @@ class CmdGrantPrivilegesToRole : public BasicCommand {
 public:
     CmdGrantPrivilegesToRole() : BasicCommand("grantPrivilegesToRole") {}
 
-    virtual bool slaveOk() const {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
 
@@ -511,11 +501,10 @@ class CmdRevokePrivilegesFromRole : public BasicCommand {
 public:
     CmdRevokePrivilegesFromRole() : BasicCommand("revokePrivilegesFromRole") {}
 
-    virtual bool slaveOk() const {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
-
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
         return true;
     }
@@ -554,11 +543,10 @@ class CmdGrantRolesToRole : public BasicCommand {
 public:
     CmdGrantRolesToRole() : BasicCommand("grantRolesToRole") {}
 
-    virtual bool slaveOk() const {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
-
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
         return true;
     }
@@ -597,11 +585,10 @@ class CmdRevokeRolesFromRole : public BasicCommand {
 public:
     CmdRevokeRolesFromRole() : BasicCommand("revokeRolesFromRole") {}
 
-    virtual bool slaveOk() const {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
-
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
         return true;
     }
@@ -640,11 +627,10 @@ class CmdDropRole : public BasicCommand {
 public:
     CmdDropRole() : BasicCommand("dropRole") {}
 
-    virtual bool slaveOk() const {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
-
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
         return true;
     }
@@ -686,8 +672,8 @@ class CmdDropAllRolesFromDatabase : public BasicCommand {
 public:
     CmdDropAllRolesFromDatabase() : BasicCommand("dropAllRolesFromDatabase") {}
 
-    virtual bool slaveOk() const {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
 
@@ -733,15 +719,10 @@ class CmdRolesInfo : public BasicCommand {
 public:
     CmdRolesInfo() : BasicCommand("rolesInfo") {}
 
-    virtual bool slaveOk() const {
-        return false;
-    }
-
-    virtual bool slaveOverrideOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kOptIn;
     }
 
-
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
         return false;
     }
@@ -770,8 +751,8 @@ class CmdInvalidateUserCache : public BasicCommand {
 public:
     CmdInvalidateUserCache() : BasicCommand("invalidateUserCache") {}
 
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
 
     virtual bool adminOnly() const {
@@ -819,11 +800,10 @@ class CmdMergeAuthzCollections : public BasicCommand {
 public:
     CmdMergeAuthzCollections() : BasicCommand("_mergeAuthzCollections") {}
 
-    virtual bool slaveOk() const {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
-
     virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
         return true;
     }
diff --git a/src/mongo/s/commands/cluster_whats_my_uri_cmd.cpp b/src/mongo/s/commands/cluster_whats_my_uri_cmd.cpp
index a44d6fbb8c1..7cd621302ba 100644
--- a/src/mongo/s/commands/cluster_whats_my_uri_cmd.cpp
+++ b/src/mongo/s/commands/cluster_whats_my_uri_cmd.cpp
@@ -38,8 +38,8 @@ class WhatsMyUriCmd : public BasicCommand {
 public:
     WhatsMyUriCmd() : BasicCommand("whatsmyuri") {}
 
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
 
 
diff --git a/src/mongo/s/commands/cluster_write_cmd.cpp b/src/mongo/s/commands/cluster_write_cmd.cpp
index bf1949d73c8..779b3993c99 100644
--- a/src/mongo/s/commands/cluster_write_cmd.cpp
+++ b/src/mongo/s/commands/cluster_write_cmd.cpp
@@ -139,8 +139,8 @@ class ClusterWriteCmd : public Command {
 public:
     virtual ~ClusterWriteCmd() {}
 
-    bool slaveOk() const final {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const final {
+        return AllowedOnSecondary::kNever;
     }
 
     bool supportsWriteConcern(const BSONObj& cmd) const final {
diff --git a/src/mongo/s/commands/commands_public.cpp b/src/mongo/s/commands/commands_public.cpp
index 4c153831450..c5e0ecb358d 100644
--- a/src/mongo/s/commands/commands_public.cpp
+++ b/src/mongo/s/commands/commands_public.cpp
@@ -151,8 +151,8 @@ class PublicGridCommand : public BasicCommand {
 protected:
     PublicGridCommand(const char* n, const char* oldname = NULL) : BasicCommand(n, oldname) {}
 
-    virtual bool slaveOk() const {
-        return true;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kAlways;
     }
 
     virtual bool adminOnly() const {
@@ -247,8 +247,8 @@ class DropIndexesCmd : public ErrmsgCommandDeprecated {
 public:
     DropIndexesCmd() : ErrmsgCommandDeprecated("dropIndexes", "deleteIndexes") {}
 
-    bool slaveOk() const override {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
     bool adminOnly() const override {
@@ -291,8 +291,8 @@ class CreateIndexesCmd : public ErrmsgCommandDeprecated {
 public:
     CreateIndexesCmd() : ErrmsgCommandDeprecated("createIndexes") {}
 
-    bool slaveOk() const override {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
     bool adminOnly() const override {
@@ -340,8 +340,8 @@ class ReIndexCmd : public ErrmsgCommandDeprecated {
 public:
     ReIndexCmd() : ErrmsgCommandDeprecated("reIndex") {}
 
-    bool slaveOk() const override {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
     bool adminOnly() const override {
@@ -384,8 +384,8 @@ class CollectionModCmd : public ErrmsgCommandDeprecated {
 public:
     CollectionModCmd() : ErrmsgCommandDeprecated("collMod") {}
 
-    bool slaveOk() const override {
-        return false;
+    AllowedOnSecondary secondaryAllowed() const override {
+        return AllowedOnSecondary::kNever;
     }
 
     bool adminOnly() const override {