SERVER-28797 move waitForReadConcern into separate file

1 files changed, 223 insertions, 0 deletions

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