Timestamp WiredTigerSnapshotManager::beginTransactionOnLocalSnapshot(
WT_SESSION* session,
IgnorePrepared ignorePrepared,
RoundUpPreparedTimestamps roundUpPreparedTimestamps) const {
WiredTigerBeginTxnBlock txnOpen(session, ignorePrepared, roundUpPreparedTimestamps);
stdx::lock_guard<stdx::mutex> lock(_localSnapshotMutex);
invariant(_localSnapshot);
LOG(3) << "begin_transaction on local snapshot " << _localSnapshot.get().toString();
auto status = txnOpen.setReadSnapshot(_localSnapshot.get());
fassert(50775, status);
txnOpen.done();
return *_localSnapshot;
}
Timestamp WiredTigerSnapshotManager::beginTransactionOnCommittedSnapshot(
WT_SESSION* session,
IgnorePrepared ignorePrepared,
RoundUpPreparedTimestamps roundUpPreparedTimestamps) const {
WiredTigerBeginTxnBlock txnOpen(session, ignorePrepared, roundUpPreparedTimestamps);
stdx::lock_guard<stdx::mutex> lock(_committedSnapshotMutex);
uassert(ErrorCodes::ReadConcernMajorityNotAvailableYet,
"Committed view disappeared while running operation",
_committedSnapshot);
auto status = txnOpen.setReadSnapshot(_committedSnapshot.get());
fassert(30635, status);
txnOpen.done();
return *_committedSnapshot;
}
Timestamp WiredTigerRecoveryUnit::_beginTransactionAtAllCommittedTimestamp(WT_SESSION* session) {
WiredTigerBeginTxnBlock txnOpen(session, _ignorePrepared);
Timestamp txnTimestamp = Timestamp(_oplogManager->fetchAllCommittedValue(session->connection));
auto status =
txnOpen.setTimestamp(txnTimestamp, WiredTigerBeginTxnBlock::RoundToOldest::kRound);
fassert(50948, status);
// Since this is not in a critical section, we might have rounded to oldest between
// calling getAllCommitted and setTimestamp. We need to get the actual read timestamp we
// used.
char buf[(2 * 8 /*bytes in hex*/) + 1 /*nul terminator*/];
auto wtstatus = session->query_timestamp(session, buf, "get=read");
invariantWTOK(wtstatus);
uint64_t read_timestamp;
fassert(50949, parseNumberFromStringWithBase(buf, 16, &read_timestamp));
txnOpen.done();
return Timestamp(read_timestamp);
}
void WiredTigerRecoveryUnit::_txnOpen() {
invariant(!_isActive(), toString(_state));
invariant(!_isCommittingOrAborting(),
str::stream() << "commit or rollback handler reopened transaction: "
<< toString(_state));
_ensureSession();
// Only start a timer for transaction's lifetime if we're going to log it.
if (shouldLog(kSlowTransactionSeverity)) {
_timer.reset(new Timer());
}
WT_SESSION* session = _session->getSession();
switch (_timestampReadSource) {
case ReadSource::kUnset:
case ReadSource::kNoTimestamp: {
WiredTigerBeginTxnBlock txnOpen(session, _ignorePrepared);
if (_isOplogReader) {
auto status =
txnOpen.setTimestamp(Timestamp(_oplogManager->getOplogReadTimestamp()),
WiredTigerBeginTxnBlock::RoundToOldest::kRound);
fassert(50771, status);
}
txnOpen.done();
break;
}
case ReadSource::kMajorityCommitted: {
// We reset _majorityCommittedSnapshot to the actual read timestamp used when the
// transaction was started.
_majorityCommittedSnapshot =
_sessionCache->snapshotManager().beginTransactionOnCommittedSnapshot(
session, _ignorePrepared);
break;
}
case ReadSource::kLastApplied: {
if (_sessionCache->snapshotManager().getLocalSnapshot()) {
_readAtTimestamp = _sessionCache->snapshotManager().beginTransactionOnLocalSnapshot(
session, _ignorePrepared);
} else {
WiredTigerBeginTxnBlock(session, _ignorePrepared).done();
}
break;
}
case ReadSource::kAllCommittedSnapshot: {
if (_readAtTimestamp.isNull()) {
_readAtTimestamp = _beginTransactionAtAllCommittedTimestamp(session);
break;
}
// Intentionally continue to the next case to read at the _readAtTimestamp.
}
case ReadSource::kLastAppliedSnapshot: {
// Only ever read the last applied timestamp once, and continue reusing it for
// subsequent transactions.
if (_readAtTimestamp.isNull()) {
_readAtTimestamp = _sessionCache->snapshotManager().beginTransactionOnLocalSnapshot(
session, _ignorePrepared);
break;
}
// Intentionally continue to the next case to read at the _readAtTimestamp.
}
case ReadSource::kProvided: {
WiredTigerBeginTxnBlock txnOpen(session, _ignorePrepared);
auto status = txnOpen.setTimestamp(_readAtTimestamp);
if (!status.isOK() && status.code() == ErrorCodes::BadValue) {
uasserted(ErrorCodes::SnapshotTooOld,
str::stream() << "Read timestamp " << _readAtTimestamp.toString()
<< " is older than the oldest available timestamp.");
}
uassertStatusOK(status);
txnOpen.done();
break;
}
}
LOG(3) << "WT begin_transaction for snapshot id " << _mySnapshotId;
}
