SERVER-28797 move waitForReadConcern into separate file

6 files changed, 303 insertions, 180 deletions

diff --git a/src/mongo/base/error_codes.err b/src/mongo/base/error_codes.err
index e816da00ae0..5284743c8ac 100644
--- a/src/mongo/base/error_codes.err
+++ b/src/mongo/base/error_codes.err
@@ -206,6 +206,7 @@ error_code("ClusterTimeFailsRateLimiter", 205);
 error_code("NoSuchSession", 206)
 error_code("InvalidUUID", 207)
 error_code("TooManyLocks", 208)
+error_code("StaleClusterTime", 209)
 
 # Error codes 4000-8999 are reserved.
 
diff --git a/src/mongo/db/SConscript b/src/mongo/db/SConscript
index 66049a93d88..0b54f6cbd63 100644
--- a/src/mongo/db/SConscript
+++ b/src/mongo/db/SConscript
@@ -773,8 +773,9 @@ env.Library(
 )
 
 env.Library(
-    target="write_concern_d",
+    target="rw_concern_d",
     source=[
+        "read_concern.cpp",
         "write_concern.cpp",
     ],
     LIBDEPS=[
@@ -785,6 +786,7 @@ env.Library(
         "repl/repl_coordinator_interface",
         "stats/timer_stats",
         "storage/storage_options",
+        "s/sharding",
     ],
 )
 
@@ -941,7 +943,7 @@ env.Library(
         "repl/sync_tail",
         "repl/topology_coordinator_impl",
         "run_commands",
-        "write_concern_d",
+        "rw_concern_d",
         "s/commands",
         "s/metadata",
         "s/sharding",
diff --git a/src/mongo/db/commands/dbcommands.cpp b/src/mongo/db/commands/dbcommands.cpp
index f3dfa5856fd..becd4501056 100644
--- a/src/mongo/db/commands/dbcommands.cpp
+++ b/src/mongo/db/commands/dbcommands.cpp
@@ -84,6 +84,7 @@
 #include "mongo/db/query/get_executor.h"
 #include "mongo/db/query/internal_plans.h"
 #include "mongo/db/query/query_planner.h"
+#include "mongo/db/read_concern.h"
 #include "mongo/db/repair_database.h"
 #include "mongo/db/repl/optime.h"
 #include "mongo/db/repl/read_concern_args.h"
@@ -106,7 +107,6 @@
 #include "mongo/rpc/reply_builder_interface.h"
 #include "mongo/rpc/request_interface.h"
 #include "mongo/s/chunk_version.h"
-#include "mongo/s/client/shard_registry.h"
 #include "mongo/s/grid.h"
 #include "mongo/s/stale_exception.h"
 #include "mongo/scripting/engine.h"
@@ -124,14 +124,6 @@ using std::unique_ptr;
 
 namespace {
 
-// This is a special flag that allows for testing of snapshot behavior by skipping the replication
-// related checks and isolating the storage/query side of snapshotting.
-bool testingSnapshotBehaviorInIsolation = false;
-ExportedServerParameter<bool, ServerParameterType::kStartupOnly> TestingSnapshotBehaviorInIsolation(
-    ServerParameterSet::getGlobal(),
-    "testingSnapshotBehaviorInIsolation",
-    &testingSnapshotBehaviorInIsolation);
-
 void registerErrorImpl(OperationContext* opCtx, const DBException& exception) {
     CurOp::get(opCtx)->debug().exceptionInfo = exception.getInfo();
 }
@@ -193,159 +185,6 @@ LogicalTime computeOperationTime(OperationContext* opCtx,
     return operationTime;
 }
 
-Status makeNoopWriteIfNeeded(OperationContext* opCtx, LogicalTime clusterTime) {
-    repl::ReplicationCoordinator* const replCoord = repl::ReplicationCoordinator::get(opCtx);
-    auto lastAppliedTime = LogicalTime(replCoord->getMyLastAppliedOpTime().getTimestamp());
-    if (clusterTime > lastAppliedTime) {
-        auto shardingState = ShardingState::get(opCtx);
-        // standalone replica set, so there is no need to advance the OpLog on the primary.
-        if (!shardingState->enabled()) {
-            return Status::OK();
-        }
-
-        auto myShard =
-            Grid::get(opCtx)->shardRegistry()->getShard(opCtx, shardingState->getShardName());
-        if (!myShard.isOK()) {
-            return myShard.getStatus();
-        }
-
-        auto swRes = myShard.getValue()->runCommand(
-            opCtx,
-            ReadPreferenceSetting(ReadPreference::PrimaryOnly),
-            "admin",
-            BSON("applyOpLogNote" << 1 << "clusterTime" << clusterTime.asTimestamp() << "data"
-                                  << BSON("append noop write" << 1)),
-            Shard::RetryPolicy::kIdempotent);
-        return swRes.getStatus();
-    }
-    return Status::OK();
-}
-
-Status waitForReadConcern(OperationContext* opCtx, const repl::ReadConcernArgs& readConcernArgs) {
-    repl::ReplicationCoordinator* const replCoord = repl::ReplicationCoordinator::get(opCtx);
-
-    if (readConcernArgs.getLevel() == repl::ReadConcernLevel::kLinearizableReadConcern) {
-        if (replCoord->getReplicationMode() != repl::ReplicationCoordinator::modeReplSet) {
-            // For master/slave and standalone nodes, Linearizable Read is not supported.
-            return {ErrorCodes::NotAReplicaSet,
-                    "node needs to be a replica set member to use read concern"};
-        }
-
-        // Replica sets running pv0 do not support linearizable read concern until further testing
-        // is completed (SERVER-27025).
-        if (!replCoord->isV1ElectionProtocol()) {
-            return {
-                ErrorCodes::IncompatibleElectionProtocol,
-                "Replica sets running protocol version 0 do not support readConcern: linearizable"};
-        }
-
-        if (readConcernArgs.getArgsOpTime()) {
-            return {ErrorCodes::FailedToParse,
-                    "afterOpTime not compatible with linearizable read concern"};
-        }
-
-        if (!replCoord->getMemberState().primary()) {
-            return {ErrorCodes::NotMaster,
-                    "cannot satisfy linearizable read concern on non-primary node"};
-        }
-    }
-
-    auto afterClusterTime = readConcernArgs.getArgsClusterTime();
-    if (afterClusterTime) {
-        auto currentTime = LogicalClock::get(opCtx)->getClusterTime().getTime();
-        if (currentTime < *afterClusterTime) {
-            return {ErrorCodes::InvalidOptions,
-                    "readConcern afterClusterTime must not be greater than clusterTime value"};
-        }
-    }
-
-    // Skip waiting for the OpTime when testing snapshot behavior
-    if (!testingSnapshotBehaviorInIsolation && !readConcernArgs.isEmpty()) {
-        if (afterClusterTime) {
-            auto status = makeNoopWriteIfNeeded(opCtx, *afterClusterTime);
-            if (!status.isOK()) {
-                LOG(1) << "failed noop write due to " << status.toString();
-            }
-        }
-
-        auto status = replCoord->waitUntilOpTimeForRead(opCtx, readConcernArgs);
-        if (!status.isOK()) {
-            return status;
-        }
-    }
-
-    if ((replCoord->getReplicationMode() == repl::ReplicationCoordinator::Mode::modeReplSet ||
-         testingSnapshotBehaviorInIsolation) &&
-        readConcernArgs.getLevel() == repl::ReadConcernLevel::kMajorityReadConcern) {
-        // ReadConcern Majority is not supported in ProtocolVersion 0.
-        if (!testingSnapshotBehaviorInIsolation && !replCoord->isV1ElectionProtocol()) {
-            return {ErrorCodes::ReadConcernMajorityNotEnabled,
-                    str::stream() << "Replica sets running protocol version 0 do not support "
-                                     "readConcern: majority"};
-        }
-
-        const int debugLevel = serverGlobalParams.clusterRole == ClusterRole::ConfigServer ? 1 : 2;
-
-        LOG(debugLevel) << "Waiting for 'committed' snapshot to be available for reading: "
-                        << readConcernArgs;
-
-        Status status = opCtx->recoveryUnit()->setReadFromMajorityCommittedSnapshot();
-
-        // Wait until a snapshot is available.
-        while (status == ErrorCodes::ReadConcernMajorityNotAvailableYet) {
-            LOG(debugLevel) << "Snapshot not available yet.";
-            replCoord->waitUntilSnapshotCommitted(opCtx, SnapshotName::min());
-            status = opCtx->recoveryUnit()->setReadFromMajorityCommittedSnapshot();
-        }
-
-        if (!status.isOK()) {
-            return status;
-        }
-
-        LOG(debugLevel) << "Using 'committed' snapshot: " << CurOp::get(opCtx)->query();
-    }
-
-    return Status::OK();
-}
-
-Status waitForLinearizableReadConcern(OperationContext* opCtx) {
-
-    repl::ReplicationCoordinator* replCoord =
-        repl::ReplicationCoordinator::get(opCtx->getClient()->getServiceContext());
-
-    {
-        Lock::DBLock lk(opCtx, "local", MODE_IX);
-        Lock::CollectionLock lock(opCtx->lockState(), "local.oplog.rs", MODE_IX);
-
-        if (!replCoord->canAcceptWritesForDatabase(opCtx, "admin")) {
-            return {ErrorCodes::NotMaster,
-                    "No longer primary when waiting for linearizable read concern"};
-        }
-
-        MONGO_WRITE_CONFLICT_RETRY_LOOP_BEGIN {
-
-            WriteUnitOfWork uow(opCtx);
-            opCtx->getClient()->getServiceContext()->getOpObserver()->onOpMessage(
-                opCtx,
-                BSON("msg"
-                     << "linearizable read"));
-            uow.commit();
-        }
-        MONGO_WRITE_CONFLICT_RETRY_LOOP_END(
-            opCtx, "waitForLinearizableReadConcern", "local.rs.oplog");
-    }
-    WriteConcernOptions wc = WriteConcernOptions(
-        WriteConcernOptions::kMajority, WriteConcernOptions::SyncMode::UNSET, 0);
-
-    repl::OpTime lastOpApplied = repl::ReplClientInfo::forClient(opCtx->getClient()).getLastOp();
-    auto awaitReplResult = replCoord->awaitReplication(opCtx, lastOpApplied, wc);
-    if (awaitReplResult.status == ErrorCodes::WriteConcernFailed) {
-        return Status(ErrorCodes::LinearizableReadConcernError,
-                      "Failed to confirm that read was linearizable.");
-    }
-    return awaitReplResult.status;
-}
-
 }  // namespace
 
 
diff --git a/src/mongo/db/commands/oplog_note.cpp b/src/mongo/db/commands/oplog_note.cpp
index abdd78901c9..9a5760d616a 100644
--- a/src/mongo/db/commands/oplog_note.cpp
+++ b/src/mongo/db/commands/oplog_note.cpp
@@ -118,15 +118,6 @@ public:
                      BSONObj& cmdObj,
                      string& errmsg,
                      BSONObjBuilder& result) {
-        BSONElement dataElement;
-        auto dataStatus = bsonExtractTypedField(cmdObj, "data", Object, &dataElement);
-        if (!dataStatus.isOK()) {
-            return appendCommandStatus(result, dataStatus);
-        }
-
-        Timestamp clusterTime;
-        auto clusterTimeStatus = bsonExtractTimestampField(cmdObj, "clusterTime", &clusterTime);
-
         auto replCoord = repl::ReplicationCoordinator::get(opCtx);
         if (!replCoord->isReplEnabled()) {
             return appendCommandStatus(result,
@@ -134,22 +125,33 @@ public:
                                         "Must have replication set up to run \"appendOplogNote\""});
         }
 
-        if (!clusterTimeStatus.isOK()) {
-            if (clusterTimeStatus == ErrorCodes::NoSuchKey) {  // no need to use clusterTime
+        BSONElement dataElement;
+        auto dataStatus = bsonExtractTypedField(cmdObj, "data", Object, &dataElement);
+        if (!dataStatus.isOK()) {
+            return appendCommandStatus(result, dataStatus);
+        }
+
+        Timestamp maxClusterTime;
+        auto maxClusterTimeStatus =
+            bsonExtractTimestampField(cmdObj, "maxClusterTime", &maxClusterTime);
+
+        if (!maxClusterTimeStatus.isOK()) {
+            if (maxClusterTimeStatus == ErrorCodes::NoSuchKey) {  // no need to use maxClusterTime
                 return appendCommandStatus(
                     result, _performNoopWrite(opCtx, dataElement.Obj(), "appendOpLogNote"));
             }
-            return appendCommandStatus(result, clusterTimeStatus);
+            return appendCommandStatus(result, maxClusterTimeStatus);
         }
 
         auto lastAppliedOpTime = replCoord->getMyLastAppliedOpTime().getTimestamp();
-        if (clusterTime > lastAppliedOpTime) {
+        if (maxClusterTime > lastAppliedOpTime) {
             return appendCommandStatus(
                 result, _performNoopWrite(opCtx, dataElement.Obj(), "appendOpLogNote"));
         } else {
-            LOG(1) << "Not scheduling a noop write. Requested clusterTime" << clusterTime
-                   << " is less or equal to the last primary OpTime: " << lastAppliedOpTime;
-            return appendCommandStatus(result, Status::OK());
+            std::stringstream ss;
+            ss << "Requested maxClusterTime" << maxClusterTime.toString()
+               << " is less or equal to the last primary OpTime: " << lastAppliedOpTime.toString();
+            return appendCommandStatus(result, {ErrorCodes::StaleClusterTime, ss.str()});
         }
     }
 };
diff --git a/src/mongo/db/read_concern.cpp b/src/mongo/db/read_concern.cpp
new file mode 100644
index 00000000000..2b3a0c7c184
--- /dev/null
+++ b/src/mongo/db/read_concern.cpp
@@ -0,0 +1,223 @@
+/**
+ *    Copyright (C) 2016 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.
+ */
+
+#define MONGO_LOG_DEFAULT_COMPONENT ::mongo::logger::LogComponent::kCommand
+
+#include "mongo/platform/basic.h"
+
+#include "mongo/db/read_concern.h"
+
+#include "mongo/base/status.h"
+#include "mongo/base/status_with.h"
+#include "mongo/db/commands.h"
+#include "mongo/db/concurrency/d_concurrency.h"
+#include "mongo/db/concurrency/write_conflict_exception.h"
+#include "mongo/db/curop.h"
+#include "mongo/db/logical_clock.h"
+#include "mongo/db/op_observer.h"
+#include "mongo/db/operation_context.h"
+#include "mongo/db/repl/read_concern_args.h"
+#include "mongo/db/repl/repl_client_info.h"
+#include "mongo/db/repl/replication_coordinator.h"
+#include "mongo/db/s/operation_sharding_state.h"
+#include "mongo/db/s/sharding_state.h"
+#include "mongo/db/server_options.h"
+#include "mongo/db/server_parameters.h"
+#include "mongo/s/client/shard_registry.h"
+#include "mongo/s/grid.h"
+#include "mongo/util/log.h"
+
+namespace mongo {
+namespace {
+
+// This is a special flag that allows for testing of snapshot behavior by skipping the replication
+// related checks and isolating the storage/query side of snapshotting.
+bool testingSnapshotBehaviorInIsolation = false;
+ExportedServerParameter<bool, ServerParameterType::kStartupOnly> TestingSnapshotBehaviorInIsolation(
+    ServerParameterSet::getGlobal(),
+    "testingSnapshotBehaviorInIsolation",
+    &testingSnapshotBehaviorInIsolation);
+
+/**
+ *  Schedule a write via appendOplogNote command to the primary of this replica set.
+ */
+Status makeNoopWriteIfNeeded(OperationContext* opCtx, LogicalTime clusterTime) {
+    repl::ReplicationCoordinator* const replCoord = repl::ReplicationCoordinator::get(opCtx);
+    auto lastAppliedTime = LogicalTime(replCoord->getMyLastAppliedOpTime().getTimestamp());
+    if (clusterTime > lastAppliedTime) {
+        auto shardingState = ShardingState::get(opCtx);
+        // standalone replica set, so there is no need to advance the OpLog on the primary.
+        if (!shardingState->enabled()) {
+            return Status::OK();
+        }
+
+        auto myShard =
+            Grid::get(opCtx)->shardRegistry()->getShard(opCtx, shardingState->getShardName());
+        if (!myShard.isOK()) {
+            return myShard.getStatus();
+        }
+
+        auto swRes = myShard.getValue()->runCommand(
+            opCtx,
+            ReadPreferenceSetting(ReadPreference::PrimaryOnly),
+            "admin",
+            BSON("appendOplogNote" << 1 << "maxClusterTime" << clusterTime.asTimestamp() << "data"
+                                   << BSON("noop write for afterClusterTime read concern" << 1)),
+            Shard::RetryPolicy::kIdempotent);
+        return swRes.getStatus();
+    }
+    return Status::OK();
+}
+}  // namespace
+
+Status waitForReadConcern(OperationContext* opCtx, const repl::ReadConcernArgs& readConcernArgs) {
+    repl::ReplicationCoordinator* const replCoord = repl::ReplicationCoordinator::get(opCtx);
+
+    if (readConcernArgs.getLevel() == repl::ReadConcernLevel::kLinearizableReadConcern) {
+        if (replCoord->getReplicationMode() != repl::ReplicationCoordinator::modeReplSet) {
+            // For master/slave and standalone nodes, Linearizable Read is not supported.
+            return {ErrorCodes::NotAReplicaSet,
+                    "node needs to be a replica set member to use read concern"};
+        }
+
+        // Replica sets running pv0 do not support linearizable read concern until further testing
+        // is completed (SERVER-27025).
+        if (!replCoord->isV1ElectionProtocol()) {
+            return {
+                ErrorCodes::IncompatibleElectionProtocol,
+                "Replica sets running protocol version 0 do not support readConcern: linearizable"};
+        }
+
+        if (readConcernArgs.getArgsOpTime()) {
+            return {ErrorCodes::FailedToParse,
+                    "afterOpTime not compatible with linearizable read concern"};
+        }
+
+        if (!replCoord->getMemberState().primary()) {
+            return {ErrorCodes::NotMaster,
+                    "cannot satisfy linearizable read concern on non-primary node"};
+        }
+    }
+
+    auto afterClusterTime = readConcernArgs.getArgsClusterTime();
+    if (afterClusterTime) {
+        auto currentTime = LogicalClock::get(opCtx)->getClusterTime().getTime();
+        if (currentTime < *afterClusterTime) {
+            return {ErrorCodes::InvalidOptions,
+                    "readConcern afterClusterTime must not be greater than clusterTime value"};
+        }
+    }
+
+    // Skip waiting for the OpTime when testing snapshot behavior
+    if (!testingSnapshotBehaviorInIsolation && !readConcernArgs.isEmpty()) {
+        if (afterClusterTime) {
+            auto status = makeNoopWriteIfNeeded(opCtx, *afterClusterTime);
+            if (!status.isOK()) {
+                LOG(1) << "failed noop write due to " << status.toString();
+            }
+        }
+
+        auto status = replCoord->waitUntilOpTimeForRead(opCtx, readConcernArgs);
+        if (!status.isOK()) {
+            return status;
+        }
+    }
+
+    if ((replCoord->getReplicationMode() == repl::ReplicationCoordinator::Mode::modeReplSet ||
+         testingSnapshotBehaviorInIsolation) &&
+        readConcernArgs.getLevel() == repl::ReadConcernLevel::kMajorityReadConcern) {
+        // ReadConcern Majority is not supported in ProtocolVersion 0.
+        if (!testingSnapshotBehaviorInIsolation && !replCoord->isV1ElectionProtocol()) {
+            return {ErrorCodes::ReadConcernMajorityNotEnabled,
+                    str::stream() << "Replica sets running protocol version 0 do not support "
+                                     "readConcern: majority"};
+        }
+
+        const int debugLevel = serverGlobalParams.clusterRole == ClusterRole::ConfigServer ? 1 : 2;
+
+        LOG(debugLevel) << "Waiting for 'committed' snapshot to be available for reading: "
+                        << readConcernArgs;
+
+        Status status = opCtx->recoveryUnit()->setReadFromMajorityCommittedSnapshot();
+
+        // Wait until a snapshot is available.
+        while (status == ErrorCodes::ReadConcernMajorityNotAvailableYet) {
+            LOG(debugLevel) << "Snapshot not available yet.";
+            replCoord->waitUntilSnapshotCommitted(opCtx, SnapshotName::min());
+            status = opCtx->recoveryUnit()->setReadFromMajorityCommittedSnapshot();
+        }
+
+        if (!status.isOK()) {
+            return status;
+        }
+
+        LOG(debugLevel) << "Using 'committed' snapshot: " << CurOp::get(opCtx)->query();
+    }
+
+    return Status::OK();
+}
+
+Status waitForLinearizableReadConcern(OperationContext* opCtx) {
+
+    repl::ReplicationCoordinator* replCoord =
+        repl::ReplicationCoordinator::get(opCtx->getClient()->getServiceContext());
+
+    {
+        Lock::DBLock lk(opCtx, "local", MODE_IX);
+        Lock::CollectionLock lock(opCtx->lockState(), "local.oplog.rs", MODE_IX);
+
+        if (!replCoord->canAcceptWritesForDatabase(opCtx, "admin")) {
+            return {ErrorCodes::NotMaster,
+                    "No longer primary when waiting for linearizable read concern"};
+        }
+
+        MONGO_WRITE_CONFLICT_RETRY_LOOP_BEGIN {
+
+            WriteUnitOfWork uow(opCtx);
+            opCtx->getClient()->getServiceContext()->getOpObserver()->onOpMessage(
+                opCtx,
+                BSON("msg"
+                     << "linearizable read"));
+            uow.commit();
+        }
+        MONGO_WRITE_CONFLICT_RETRY_LOOP_END(
+            opCtx, "waitForLinearizableReadConcern", "local.rs.oplog");
+    }
+    WriteConcernOptions wc = WriteConcernOptions(
+        WriteConcernOptions::kMajority, WriteConcernOptions::SyncMode::UNSET, 0);
+
+    repl::OpTime lastOpApplied = repl::ReplClientInfo::forClient(opCtx->getClient()).getLastOp();
+    auto awaitReplResult = replCoord->awaitReplication(opCtx, lastOpApplied, wc);
+    if (awaitReplResult.status == ErrorCodes::WriteConcernFailed) {
+        return Status(ErrorCodes::LinearizableReadConcernError,
+                      "Failed to confirm that read was linearizable.");
+    }
+    return awaitReplResult.status;
+}
+
+}  // namespace mongo
diff --git a/src/mongo/db/read_concern.h b/src/mongo/db/read_concern.h
new file mode 100644
index 00000000000..8c01e902f01
--- /dev/null
+++ b/src/mongo/db/read_concern.h
@@ -0,0 +1,56 @@
+/**
+ *    Copyright (C) 2016 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
+
+namespace mongo {
+
+class BSONObj;
+class OperationContext;
+class Status;
+template <typename T>
+class StatusWith;
+namespace repl {
+class ReadConcernArgs;
+}
+
+
+/**
+ * Given the specified read concern arguments, performs checks that the read concern can actually be
+ * satisfied given the current state of the server and if so calls into the replication subsystem to
+ * perform the wait.
+ */
+Status waitForReadConcern(OperationContext* opCtx, const repl::ReadConcernArgs& readConcernArgs);
+
+/*
+ * Given a linearizable read command, confirm that
+ * current primary is still the true primary of the replica set.
+ */
+Status waitForLinearizableReadConcern(OperationContext* opCtx);
+
+}  // namespace mongo