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/**
* 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/write_conflict_exception.h"
#include "mongo/db/curop.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/server_options.h"
#include "mongo/db/server_parameters.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);
} // namespace
StatusWith<repl::ReadConcernArgs> extractReadConcern(OperationContext* txn,
const BSONObj& cmdObj,
bool supportsReadConcern) {
repl::ReadConcernArgs readConcernArgs;
auto readConcernParseStatus = readConcernArgs.initialize(cmdObj);
if (!readConcernParseStatus.isOK()) {
return readConcernParseStatus;
}
if (!supportsReadConcern && !readConcernArgs.isEmpty()) {
return {ErrorCodes::InvalidOptions,
str::stream() << "Command does not support read concern"};
}
return readConcernArgs;
}
Status waitForReadConcern(OperationContext* txn, const repl::ReadConcernArgs& readConcernArgs) {
repl::ReplicationCoordinator* const replCoord = repl::ReplicationCoordinator::get(txn);
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"};
}
if (!replCoord->getSettings().isMajorityReadConcernEnabled()) {
// This is an opt-in feature. Fail if the user didn't opt-in.
return {ErrorCodes::ReadConcernMajorityNotEnabled,
"Linearizable read concern requested, but server was not started with "
"--enableMajorityReadConcern."};
}
if (!readConcernArgs.getOpTime().isNull()) {
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"};
}
}
// Skip waiting for the OpTime when testing snapshot behavior
if (!testingSnapshotBehaviorInIsolation && !readConcernArgs.isEmpty()) {
Status status = replCoord->waitUntilOpTimeForRead(txn, readConcernArgs);
if (!status.isOK()) {
return status;
}
}
if ((replCoord->getReplicationMode() == repl::ReplicationCoordinator::Mode::modeReplSet ||
testingSnapshotBehaviorInIsolation) &&
(readConcernArgs.getLevel() == repl::ReadConcernLevel::kMajorityReadConcern ||
readConcernArgs.getLevel() == repl::ReadConcernLevel::kLinearizableReadConcern)) {
// 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 = txn->recoveryUnit()->setReadFromMajorityCommittedSnapshot();
// Wait until a snapshot is available.
while (status == ErrorCodes::ReadConcernMajorityNotAvailableYet) {
LOG(debugLevel) << "Snapshot not available yet.";
replCoord->waitUntilSnapshotCommitted(txn, SnapshotName::min());
status = txn->recoveryUnit()->setReadFromMajorityCommittedSnapshot();
}
if (!status.isOK()) {
return status;
}
LOG(debugLevel) << "Using 'committed' snapshot: " << CurOp::get(txn)->query();
}
return Status::OK();
}
Status waitForLinearizableReadConcern(OperationContext* txn) {
repl::ReplicationCoordinator* replCoord =
repl::ReplicationCoordinator::get(txn->getClient()->getServiceContext());
{
ScopedTransaction transaction(txn, MODE_IX);
Lock::DBLock lk(txn->lockState(), "local", MODE_IX);
Lock::CollectionLock lock(txn->lockState(), "local.oplog.rs", MODE_IX);
MONGO_WRITE_CONFLICT_RETRY_LOOP_BEGIN {
WriteUnitOfWork uow(txn);
txn->getClient()->getServiceContext()->getOpObserver()->onOpMessage(
txn,
BSON("msg"
<< "linearizable read"));
uow.commit();
}
MONGO_WRITE_CONFLICT_RETRY_LOOP_END(
txn, "waitForLinearizableReadConcern", "local.rs.oplog");
}
WriteConcernOptions wc = WriteConcernOptions(
WriteConcernOptions::kMajority, WriteConcernOptions::SyncMode::UNSET, 0);
repl::OpTime lastOpApplied = repl::ReplClientInfo::forClient(txn->getClient()).getLastOp();
auto awaitReplResult = replCoord->awaitReplication(txn, lastOpApplied, wc);
if (awaitReplResult.status == ErrorCodes::WriteConcernFailed) {
return Status(ErrorCodes::LinearizableReadConcernError,
"Failed to confirm that read was linearizable.");
}
return awaitReplResult.status;
}
} // namespace mongo
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