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"};
}
// 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.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) {
// 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();
}
