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// wiredtiger_recovery_unit.cpp
/**
* Copyright (C) 2014 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::kStorage
#include "mongo/platform/basic.h"
#include "mongo/db/storage/wiredtiger/wiredtiger_recovery_unit.h"
#include "mongo/bson/bsonobjbuilder.h"
#include "mongo/db/server_options.h"
#include "mongo/db/storage/wiredtiger/wiredtiger_begin_transaction_block.h"
#include "mongo/db/storage/wiredtiger/wiredtiger_kv_engine.h"
#include "mongo/db/storage/wiredtiger/wiredtiger_prepare_conflict.h"
#include "mongo/db/storage/wiredtiger/wiredtiger_session_cache.h"
#include "mongo/db/storage/wiredtiger/wiredtiger_util.h"
#include "mongo/util/hex.h"
#include "mongo/util/log.h"
namespace mongo {
namespace {
// Always notifies prepare conflict waiters when a transaction commits or aborts, even when the
// transaction is not prepared. This should always be enabled if WTPrepareConflictForReads is
// used, which fails randomly. If this is not enabled, no prepare conflicts will be resolved,
// because the recovery unit may not ever actually be in a prepared state.
MONGO_FAIL_POINT_DEFINE(WTAlwaysNotifyPrepareConflictWaiters);
// SnapshotIds need to be globally unique, as they are used in a WorkingSetMember to
// determine if documents changed, but a different recovery unit may be used across a getMore,
// so there is a chance the snapshot ID will be reused.
AtomicUInt64 nextSnapshotId{1};
logger::LogSeverity kSlowTransactionSeverity = logger::LogSeverity::Debug(1);
} // namespace
WiredTigerRecoveryUnit::WiredTigerRecoveryUnit(WiredTigerSessionCache* sc)
: WiredTigerRecoveryUnit(sc, sc->getKVEngine()->getOplogManager()) {}
WiredTigerRecoveryUnit::WiredTigerRecoveryUnit(WiredTigerSessionCache* sc,
WiredTigerOplogManager* oplogManager)
: _sessionCache(sc),
_oplogManager(oplogManager),
_inUnitOfWork(false),
_active(false),
_mySnapshotId(nextSnapshotId.fetchAndAdd(1)) {}
WiredTigerRecoveryUnit::~WiredTigerRecoveryUnit() {
invariant(!_inUnitOfWork);
_abort();
}
void WiredTigerRecoveryUnit::_commit() {
// Since we cannot have both a _lastTimestampSet and a _commitTimestamp, we set the
// commit time as whichever is non-empty. If both are empty, then _lastTimestampSet will
// be boost::none and we'll set the commit time to that.
auto commitTime = _commitTimestamp.isNull() ? _lastTimestampSet : _commitTimestamp;
try {
bool notifyDone = !_prepareTimestamp.isNull();
if (_session && _active) {
_txnClose(true);
}
if (MONGO_FAIL_POINT(WTAlwaysNotifyPrepareConflictWaiters)) {
notifyDone = true;
}
if (notifyDone) {
_sessionCache->notifyPreparedUnitOfWorkHasCommittedOrAborted();
}
for (Changes::const_iterator it = _changes.begin(), end = _changes.end(); it != end; ++it) {
(*it)->commit(commitTime);
}
_changes.clear();
invariant(!_active);
} catch (...) {
std::terminate();
}
}
void WiredTigerRecoveryUnit::_abort() {
try {
bool notifyDone = !_prepareTimestamp.isNull();
if (_session && _active) {
_txnClose(false);
}
if (MONGO_FAIL_POINT(WTAlwaysNotifyPrepareConflictWaiters)) {
notifyDone = true;
}
if (notifyDone) {
_sessionCache->notifyPreparedUnitOfWorkHasCommittedOrAborted();
}
for (Changes::const_reverse_iterator it = _changes.rbegin(), end = _changes.rend();
it != end;
++it) {
Change* change = it->get();
LOG(2) << "CUSTOM ROLLBACK " << redact(demangleName(typeid(*change)));
change->rollback();
}
_changes.clear();
invariant(!_active);
} catch (...) {
std::terminate();
}
}
void WiredTigerRecoveryUnit::beginUnitOfWork(OperationContext* opCtx) {
invariant(!_areWriteUnitOfWorksBanned);
invariant(!_inUnitOfWork);
_inUnitOfWork = true;
}
void WiredTigerRecoveryUnit::prepareUnitOfWork() {
invariant(!_areWriteUnitOfWorksBanned);
invariant(_inUnitOfWork);
invariant(!_prepareTimestamp.isNull());
auto session = getSession();
WT_SESSION* s = session->getSession();
LOG(1) << "preparing transaction at time: " << _prepareTimestamp;
const std::string conf = "prepare_timestamp=" + integerToHex(_prepareTimestamp.asULL());
// Prepare the transaction.
invariantWTOK(s->prepare_transaction(s, conf.c_str()));
}
void WiredTigerRecoveryUnit::commitUnitOfWork() {
invariant(_inUnitOfWork);
_inUnitOfWork = false;
_commit();
}
void WiredTigerRecoveryUnit::abortUnitOfWork() {
invariant(_inUnitOfWork);
_inUnitOfWork = false;
_abort();
}
void WiredTigerRecoveryUnit::_ensureSession() {
if (!_session) {
_session = _sessionCache->getSession();
}
}
bool WiredTigerRecoveryUnit::waitUntilDurable() {
invariant(!_inUnitOfWork);
const bool forceCheckpoint = false;
const bool stableCheckpoint = false;
_sessionCache->waitUntilDurable(forceCheckpoint, stableCheckpoint);
return true;
}
bool WiredTigerRecoveryUnit::waitUntilUnjournaledWritesDurable() {
invariant(!_inUnitOfWork);
const bool forceCheckpoint = true;
const bool stableCheckpoint = true;
// Calling `waitUntilDurable` with `forceCheckpoint` set to false only performs a log
// (journal) flush, and thus has no effect on unjournaled writes. Setting `forceCheckpoint` to
// true will lock in stable writes to unjournaled tables.
_sessionCache->waitUntilDurable(forceCheckpoint, stableCheckpoint);
return true;
}
void WiredTigerRecoveryUnit::registerChange(Change* change) {
invariant(_inUnitOfWork);
_changes.push_back(std::unique_ptr<Change>{change});
}
void WiredTigerRecoveryUnit::assertInActiveTxn() const {
fassert(28575, _active);
}
WiredTigerSession* WiredTigerRecoveryUnit::getSession() {
if (!_active) {
_txnOpen();
}
return _session.get();
}
WiredTigerSession* WiredTigerRecoveryUnit::getSessionNoTxn() {
_ensureSession();
WiredTigerSession* session = _session.get();
// Handling queued drops can be slow, which is not desired for internal operations like FTDC
// sampling. Disable handling of queued drops for such sessions.
session->dropQueuedIdentsAtSessionEndAllowed(false);
return session;
}
void WiredTigerRecoveryUnit::abandonSnapshot() {
invariant(!_inUnitOfWork);
if (_active) {
// Can't be in a WriteUnitOfWork, so safe to rollback
_txnClose(false);
}
_areWriteUnitOfWorksBanned = false;
}
void WiredTigerRecoveryUnit::preallocateSnapshot() {
// Begin a new transaction, if one is not already started.
getSession();
}
void* WiredTigerRecoveryUnit::writingPtr(void* data, size_t len) {
// This API should not be used for anything other than the MMAP V1 storage engine
MONGO_UNREACHABLE;
}
void WiredTigerRecoveryUnit::_txnClose(bool commit) {
invariant(_active);
WT_SESSION* s = _session->getSession();
if (_timer) {
const int transactionTime = _timer->millis();
if (transactionTime >= serverGlobalParams.slowMS) {
LOG(kSlowTransactionSeverity) << "Slow WT transaction. Lifetime of SnapshotId "
<< _mySnapshotId << " was " << transactionTime << "ms";
}
}
int wtRet;
if (commit) {
if (!_commitTimestamp.isNull()) {
const std::string conf = "commit_timestamp=" + integerToHex(_commitTimestamp.asULL());
invariantWTOK(s->timestamp_transaction(s, conf.c_str()));
_isTimestamped = true;
}
wtRet = s->commit_transaction(s, nullptr);
LOG(3) << "WT commit_transaction for snapshot id " << _mySnapshotId;
} else {
wtRet = s->rollback_transaction(s, nullptr);
invariant(!wtRet);
LOG(3) << "WT rollback_transaction for snapshot id " << _mySnapshotId;
}
if (_isTimestamped) {
if (!_orderedCommit) {
// We only need to update oplog visibility where commits can be out-of-order with
// respect to their assigned optime and such commits might otherwise be visible.
// This should happen only on primary nodes.
_oplogManager->triggerJournalFlush();
}
_isTimestamped = false;
}
invariantWTOK(wtRet);
invariant(!_lastTimestampSet || _commitTimestamp.isNull(),
str::stream() << "Cannot have both a _lastTimestampSet and a "
"_commitTimestamp. _lastTimestampSet: "
<< _lastTimestampSet->toString()
<< ". _commitTimestamp: "
<< _commitTimestamp.toString());
// We reset the _lastTimestampSet between transactions. Since it is legal for one
// transaction on a RecoveryUnit to call setTimestamp() and another to call
// setCommitTimestamp().
_lastTimestampSet = boost::none;
_active = false;
_prepareTimestamp = Timestamp();
_mySnapshotId = nextSnapshotId.fetchAndAdd(1);
_isOplogReader = false;
_orderedCommit = true; // Default value is true; we assume all writes are ordered.
}
SnapshotId WiredTigerRecoveryUnit::getSnapshotId() const {
// TODO: use actual wiredtiger txn id
return SnapshotId(_mySnapshotId);
}
Status WiredTigerRecoveryUnit::obtainMajorityCommittedSnapshot() {
invariant(_timestampReadSource == ReadSource::kMajorityCommitted);
auto snapshotName = _sessionCache->snapshotManager().getMinSnapshotForNextCommittedRead();
if (!snapshotName) {
return {ErrorCodes::ReadConcernMajorityNotAvailableYet,
"Read concern majority reads are currently not possible."};
}
_majorityCommittedSnapshot = *snapshotName;
return Status::OK();
}
boost::optional<Timestamp> WiredTigerRecoveryUnit::getPointInTimeReadTimestamp() const {
if (_timestampReadSource == ReadSource::kProvided ||
_timestampReadSource == ReadSource::kLastAppliedSnapshot) {
invariant(!_readAtTimestamp.isNull());
return _readAtTimestamp;
}
if (_timestampReadSource == ReadSource::kLastApplied && !_readAtTimestamp.isNull()) {
return _readAtTimestamp;
}
if (_timestampReadSource == ReadSource::kMajorityCommitted) {
invariant(!_majorityCommittedSnapshot.isNull());
return _majorityCommittedSnapshot;
}
return boost::none;
}
void WiredTigerRecoveryUnit::_txnOpen() {
invariant(!_active);
_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::kNone: {
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);
break;
}
case ReadSource::kLastApplied: {
if (_sessionCache->snapshotManager().getLocalSnapshot()) {
_readAtTimestamp = _sessionCache->snapshotManager().beginTransactionOnLocalSnapshot(
session, _ignorePrepared);
} else {
WiredTigerBeginTxnBlock(session, _ignorePrepared).done();
}
break;
}
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;
_active = true;
}
Status WiredTigerRecoveryUnit::setTimestamp(Timestamp timestamp) {
_ensureSession();
LOG(3) << "WT set timestamp of future write operations to " << timestamp;
WT_SESSION* session = _session->getSession();
invariant(_inUnitOfWork);
invariant(_prepareTimestamp.isNull());
invariant(_commitTimestamp.isNull(),
str::stream() << "Commit timestamp set to " << _commitTimestamp.toString()
<< " and trying to set WUOW timestamp to "
<< timestamp.toString());
_lastTimestampSet = timestamp;
// Starts the WT transaction associated with this session.
getSession();
const std::string conf = "commit_timestamp=" + integerToHex(timestamp.asULL());
auto rc = session->timestamp_transaction(session, conf.c_str());
if (rc == 0) {
_isTimestamped = true;
}
return wtRCToStatus(rc, "timestamp_transaction");
}
void WiredTigerRecoveryUnit::setCommitTimestamp(Timestamp timestamp) {
invariant(!_inUnitOfWork);
invariant(_commitTimestamp.isNull(),
str::stream() << "Commit timestamp set to " << _commitTimestamp.toString()
<< " and trying to set it to "
<< timestamp.toString());
invariant(!_lastTimestampSet,
str::stream() << "Last timestamp set is " << _lastTimestampSet->toString()
<< " and trying to set commit timestamp to "
<< timestamp.toString());
invariant(!_isTimestamped);
_commitTimestamp = timestamp;
}
Timestamp WiredTigerRecoveryUnit::getCommitTimestamp() {
return _commitTimestamp;
}
void WiredTigerRecoveryUnit::clearCommitTimestamp() {
invariant(!_inUnitOfWork);
invariant(!_commitTimestamp.isNull());
invariant(!_lastTimestampSet,
str::stream() << "Last timestamp set is " << _lastTimestampSet->toString()
<< " and trying to clear commit timestamp.");
invariant(!_isTimestamped);
_commitTimestamp = Timestamp();
}
void WiredTigerRecoveryUnit::setPrepareTimestamp(Timestamp timestamp) {
invariant(_inUnitOfWork);
invariant(_prepareTimestamp.isNull());
invariant(_commitTimestamp.isNull());
_prepareTimestamp = timestamp;
}
void WiredTigerRecoveryUnit::setIgnorePrepared(bool value) {
_ignorePrepared = (value) ? WiredTigerBeginTxnBlock::IgnorePrepared::kIgnore
: WiredTigerBeginTxnBlock::IgnorePrepared::kNoIgnore;
}
void WiredTigerRecoveryUnit::setTimestampReadSource(ReadSource readSource,
boost::optional<Timestamp> provided) {
LOG(3) << "setting timestamp read source: " << static_cast<int>(readSource)
<< ", provided timestamp: " << ((provided) ? provided->toString() : "none");
invariant(!_active || _timestampReadSource == ReadSource::kNone ||
_timestampReadSource == readSource);
invariant(!provided == (readSource != ReadSource::kProvided));
invariant(!(provided && provided->isNull()));
_timestampReadSource = readSource;
_readAtTimestamp = (provided) ? *provided : Timestamp();
}
RecoveryUnit::ReadSource WiredTigerRecoveryUnit::getTimestampReadSource() const {
return _timestampReadSource;
}
void WiredTigerRecoveryUnit::beginIdle() {
// Close all cursors, we don't want to keep any old cached cursors around.
if (_session) {
_session->closeAllCursors("");
}
}
// ---------------------
WiredTigerCursor::WiredTigerCursor(const std::string& uri,
uint64_t tableId,
bool forRecordStore,
OperationContext* opCtx) {
_tableID = tableId;
_ru = WiredTigerRecoveryUnit::get(opCtx);
_session = _ru->getSession();
_cursor = _session->getCursor(uri, tableId, forRecordStore);
if (!_cursor) {
error() << "no cursor for uri: " << uri;
}
}
WiredTigerCursor::~WiredTigerCursor() {
_session->releaseCursor(_tableID, _cursor);
_cursor = NULL;
}
void WiredTigerCursor::reset() {
invariantWTOK(_cursor->reset(_cursor));
}
}
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