SERVER-62261: Implement getClusterParameter command on mongod and mongos

10 files changed, 185 insertions, 11 deletions

diff --git a/src/mongo/db/auth/action_type.idl b/src/mongo/db/auth/action_type.idl
index dc11b26fb4a..6cfbd32d0a9 100644
--- a/src/mongo/db/auth/action_type.idl
+++ b/src/mongo/db/auth/action_type.idl
@@ -97,6 +97,7 @@ enums:
            forceUUID :  "forceUUID"
            fsync :  "fsync"
            getChangeStreamOptions: "getChangeStreamOptions"
+           getClusterParameter: "getClusterParameter"
            getDatabaseVersion :  "getDatabaseVersion"
            getDefaultRWConcern :  "getDefaultRWConcern"
            getCmdLineOpts :  "getCmdLineOpts"
diff --git a/src/mongo/db/auth/builtin_roles.cpp b/src/mongo/db/auth/builtin_roles.cpp
index cbad7142669..70331b72391 100644
--- a/src/mongo/db/auth/builtin_roles.cpp
+++ b/src/mongo/db/auth/builtin_roles.cpp
@@ -255,7 +255,8 @@ MONGO_INITIALIZER(AuthorizationBuiltinRoles)(InitializerContext* context) {
         << ActionType::setFreeMonitoring
         << ActionType::setChangeStreamOptions
         << ActionType::getChangeStreamOptions
-        << ActionType::setClusterParameter;
+        << ActionType::setClusterParameter
+        << ActionType::getClusterParameter;
 
     clusterManagerRoleDatabaseActions
         << ActionType::clearJumboFlag
diff --git a/src/mongo/db/commands/SConscript b/src/mongo/db/commands/SConscript
index d28bd5d286b..cd2f7b33a87 100644
--- a/src/mongo/db/commands/SConscript
+++ b/src/mongo/db/commands/SConscript
@@ -322,9 +322,9 @@ env.Library(
 )
 
 env.Library(
-    target='set_cluster_parameter_idl',
+    target='cluster_server_parameter_cmds_idl',
     source=[
-        'set_cluster_parameter.idl',
+        'cluster_server_parameter_cmds.idl',
     ],
     LIBDEPS=[
         '$BUILD_DIR/mongo/base',
@@ -535,6 +535,7 @@ env.Library(
         "dbcommands_d.cpp",
         "dbhash.cpp",
         "driverHelpers.cpp",
+        'get_cluster_parameter_command.cpp',
         "internal_rename_if_options_and_indexes_match_cmd.cpp",
         "fle2_compact_cmd.cpp",
         "map_reduce_command.cpp",
@@ -638,7 +639,7 @@ env.Library(
     LIBDEPS=[
         '$BUILD_DIR/mongo/base',
         '$BUILD_DIR/mongo/s/write_ops/cluster_write_ops',
-        'set_cluster_parameter_idl'
+        'cluster_server_parameter_cmds_idl'
     ],
 )
 
@@ -849,4 +850,4 @@ env.CppUnitTest(
         "set_cluster_parameter_invocation",
         "standalone",
     ],
-)
\ No newline at end of file
+)
diff --git a/src/mongo/db/commands/set_cluster_parameter.idl b/src/mongo/db/commands/cluster_server_parameter_cmds.idl
index b20af08dc8e..9c768f43f23 100644
--- a/src/mongo/db/commands/set_cluster_parameter.idl
+++ b/src/mongo/db/commands/cluster_server_parameter_cmds.idl
@@ -27,17 +27,34 @@
 #
 
 global:
-    cpp_namespace: "mongo"
+    cpp_namespace: "mongo"  
 
 imports:
     - "mongo/idl/basic_types.idl"
 
+structs:
+    GetClusterParameterReply:
+        description: "Reply to getClusterParameter command"
+        fields:
+            clusterParameters: array<object>
+
 commands:
     setClusterParameter:
-        description: Command to set a ClusterServerParameter
+        description: "Command to set a ClusterServerParameter"
         command_name: setClusterParameter
         cpp_name: SetClusterParameter
         api_version: ""
         namespace: type
         type: object
         strict: true
+    
+    getClusterParameter:
+        description: "Retrieves the in-memory value of the specified cluster server parameter(s)"
+        command_name: getClusterParameter
+        cpp_name: GetClusterParameter
+        api_version: ""
+        namespace: type
+        type:
+            variant: [string, array<string>] 
+        reply_type: GetClusterParameterReply
+        strict: false 
diff --git a/src/mongo/db/commands/get_cluster_parameter_command.cpp b/src/mongo/db/commands/get_cluster_parameter_command.cpp
new file mode 100644
index 00000000000..76f6f91c590
--- /dev/null
+++ b/src/mongo/db/commands/get_cluster_parameter_command.cpp
@@ -0,0 +1,142 @@
+/**
+ *    Copyright (C) 2022-present MongoDB, Inc.
+ *
+ *    This program is free software: you can redistribute it and/or modify
+ *    it under the terms of the Server Side Public License, version 1,
+ *    as published by MongoDB, Inc.
+ *
+ *    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
+ *    Server Side Public License for more details.
+ *
+ *    You should have received a copy of the Server Side Public License
+ *    along with this program. If not, see
+ *    <http://www.mongodb.com/licensing/server-side-public-license>.
+ *
+ *    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 Server Side 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.
+ */
+
+#define MONGO_LOGV2_DEFAULT_COMPONENT ::mongo::logv2::LogComponent::kCommand
+
+#include "mongo/platform/basic.h"
+
+#include "mongo/db/auth/authorization_session.h"
+#include "mongo/db/commands.h"
+#include "mongo/db/commands/cluster_server_parameter_cmds_gen.h"
+#include "mongo/idl/cluster_server_parameter_gen.h"
+#include "mongo/logv2/log.h"
+
+namespace mongo {
+
+namespace {
+
+class GetClusterParameterCommand final : public TypedCommand<GetClusterParameterCommand> {
+public:
+    using Request = GetClusterParameter;
+    using Reply = GetClusterParameter::Reply;
+    using Map = ServerParameterSet::Map;
+
+    AllowedOnSecondary secondaryAllowed(ServiceContext*) const override {
+        return AllowedOnSecondary::kAlways;
+    }
+
+    bool adminOnly() const override {
+        return true;
+    }
+
+    std::string help() const override {
+        return "Get in-memory cluster parameter value(s) from this node";
+    }
+
+    class Invocation final : public InvocationBase {
+    public:
+        using InvocationBase::InvocationBase;
+
+        Reply typedRun(OperationContext* opCtx) {
+            uassert(
+                ErrorCodes::IllegalOperation,
+                "featureFlagClusterWideConfig not enabled",
+                gFeatureFlagClusterWideConfig.isEnabled(serverGlobalParams.featureCompatibility));
+
+            const stdx::variant<std::string, std::vector<std::string>>& cmdBody =
+                request().getCommandParameter();
+            ServerParameterSet* clusterParameters = ServerParameterSet::getClusterParameterSet();
+            std::vector<BSONObj> parameterValues;
+            std::vector<std::string> parameterNames;
+
+            // For each parameter, generate a BSON representation of it and retrieve its name.
+            auto makeBSON = [&](ServerParameter* requestedParameter) {
+                BSONObjBuilder bob;
+                bob.append("_id"_sd, requestedParameter->name());
+                requestedParameter->append(opCtx, bob, requestedParameter->name());
+                parameterValues.push_back(bob.obj());
+                parameterNames.push_back(requestedParameter->name());
+            };
+
+            stdx::visit(
+                visit_helper::Overloaded{
+                    [&](const std::string& strParameterName) {
+                        if (strParameterName == "*"_sd) {
+                            // Retrieve all cluster parameter values.
+                            Map clusterParameterMap = clusterParameters->getMap();
+                            parameterValues.reserve(clusterParameterMap.size());
+                            parameterNames.reserve(clusterParameterMap.size());
+                            for (const auto& param : clusterParameterMap) {
+                                makeBSON(param.second);
+                            }
+                        } else {
+                            // Any other string must correspond to a single parameter name.
+                            ServerParameter* sp = clusterParameters->get(strParameterName);
+                            makeBSON(sp);
+                        }
+                    },
+                    [&](const std::vector<std::string>& listParameterNames) {
+                        parameterValues.reserve(listParameterNames.size());
+                        parameterNames.reserve(listParameterNames.size());
+                        for (const auto& requestedParameterName : listParameterNames) {
+                            ServerParameter* sp = clusterParameters->get(requestedParameterName);
+                            makeBSON(sp);
+                        }
+                    }},
+                cmdBody);
+
+            LOGV2_DEBUG(6226100,
+                        2,
+                        "Retrieved parameter values for cluster server parameters",
+                        "parameterNames"_attr = parameterNames);
+
+            return Reply(parameterValues);
+        }
+
+    private:
+        bool supportsWriteConcern() const override {
+            return false;
+        }
+
+        void doCheckAuthorization(OperationContext* opCtx) const override {
+            auto* authzSession = AuthorizationSession::get(opCtx->getClient());
+            uassert(ErrorCodes::Unauthorized,
+                    "Not authorized to retrieve cluster server parameters",
+                    authzSession->isAuthorizedForPrivilege(Privilege{
+                        ResourcePattern::forClusterResource(), ActionType::getClusterParameter}));
+        }
+
+        NamespaceString ns() const override {
+            return NamespaceString(request().getDbName(), "");
+        }
+    };
+} getClusterParameterCommand;
+
+}  // namespace
+}  // namespace mongo
diff --git a/src/mongo/db/commands/set_cluster_parameter_command.cpp b/src/mongo/db/commands/set_cluster_parameter_command.cpp
index b5285dbeae3..9d4074ac0bc 100644
--- a/src/mongo/db/commands/set_cluster_parameter_command.cpp
+++ b/src/mongo/db/commands/set_cluster_parameter_command.cpp
@@ -27,13 +27,16 @@
  *    it in the license file.
  */
 
+#define MONGO_LOGV2_DEFAULT_COMPONENT ::mongo::logv2::LogComponent::kCommand
+
 #include "mongo/platform/basic.h"
 
 #include "mongo/db/auth/authorization_session.h"
 #include "mongo/db/commands.h"
-#include "mongo/db/commands/set_cluster_parameter_gen.h"
+#include "mongo/db/commands/cluster_server_parameter_cmds_gen.h"
 #include "mongo/db/commands/set_cluster_parameter_invocation.h"
 #include "mongo/idl/cluster_server_parameter_gen.h"
+#include "mongo/logv2/log.h"
 
 namespace mongo {
 
@@ -94,5 +97,6 @@ public:
         }
     };
 } setClusterParameterCommand;
+
 }  // namespace
 }  // namespace mongo
diff --git a/src/mongo/db/commands/set_cluster_parameter_invocation.cpp b/src/mongo/db/commands/set_cluster_parameter_invocation.cpp
index 4cb1087996a..513ae376564 100644
--- a/src/mongo/db/commands/set_cluster_parameter_invocation.cpp
+++ b/src/mongo/db/commands/set_cluster_parameter_invocation.cpp
@@ -31,10 +31,10 @@
 
 #include "mongo/platform/basic.h"
 
+#include "mongo/db/commands/set_cluster_parameter_invocation.h"
+
 #include "mongo/db/auth/authorization_session.h"
 #include "mongo/db/commands.h"
-#include "mongo/db/commands/set_cluster_parameter_gen.h"
-#include "mongo/db/commands/set_cluster_parameter_invocation.h"
 #include "mongo/db/vector_clock.h"
 #include "mongo/idl/cluster_server_parameter_gen.h"
 #include "mongo/logv2/log.h"
diff --git a/src/mongo/db/commands/set_cluster_parameter_invocation.h b/src/mongo/db/commands/set_cluster_parameter_invocation.h
index 6077ccac5d9..35b74530a95 100644
--- a/src/mongo/db/commands/set_cluster_parameter_invocation.h
+++ b/src/mongo/db/commands/set_cluster_parameter_invocation.h
@@ -27,7 +27,9 @@
  *    it in the license file.
  */
 
-#include "mongo/db/commands/set_cluster_parameter_gen.h"
+#pragma once
+
+#include "mongo/db/commands/cluster_server_parameter_cmds_gen.h"
 #include "mongo/db/dbdirectclient.h"
 #include "mongo/db/dbhelpers.h"
 
diff --git a/src/mongo/db/namespace_string.cpp b/src/mongo/db/namespace_string.cpp
index 2eab32c841f..649423f106b 100644
--- a/src/mongo/db/namespace_string.cpp
+++ b/src/mongo/db/namespace_string.cpp
@@ -162,6 +162,9 @@ const NamespaceString NamespaceString::kUserWritesCriticalSectionsNamespace(
 const NamespaceString NamespaceString::kCompactStructuredEncryptionCoordinatorNamespace(
     NamespaceString::kConfigDb, "compact_structured_encryption_coordinator");
 
+const NamespaceString NamespaceString::kClusterParametersNamespace(NamespaceString::kConfigDb,
+                                                                   "clusterParameters");
+
 bool NamespaceString::isListCollectionsCursorNS() const {
     return coll() == listCollectionsCursorCol;
 }
diff --git a/src/mongo/db/namespace_string.h b/src/mongo/db/namespace_string.h
index 599f5aac11f..4d1dba82f83 100644
--- a/src/mongo/db/namespace_string.h
+++ b/src/mongo/db/namespace_string.h
@@ -216,6 +216,9 @@ public:
     // Namespace used for CompactParticipantCoordinator service.
     static const NamespaceString kCompactStructuredEncryptionCoordinatorNamespace;
 
+    // Namespace used for storing cluster wide parameters.
+    static const NamespaceString kClusterParametersNamespace;
+
     /**
      * Constructs an empty NamespaceString.
      */