ssize_t
Reader::_rollback ( void )
{
//PWSHOWMETHOD();
auto& top(m_status.top());
if ( top.index not_eq top.count ) return m_cont.size();
if ( m_status.size() == 1 )
{
m_cont.push(std::move(top.node));
m_status.pop();
return m_cont.size();
}
Value tmp(top.node);
m_status.pop();
auto& top2(m_status.top());
top2.node[top2.index].assign(std::move(tmp));
++top2.index;
if ( top2.index == top2.count )
{
return _rollback();
}
return m_cont.size();
}
static bool _kvdb_upgrade(kvdb k)
{
/* Start transaction */
_begin(k);
int schema = _kvdb_get_schema(k);
if (schema < 0 || schema >= LATEST_SCHEMA)
{
KVDEBUG("schema out of range: %d/%d", schema, (int) LATEST_SCHEMA);
_rollback(k);
return false;
}
sqlite3_stmt *stmt;
const char *left = _schema_upgrades[schema];
while (left && strlen(left)>0)
{
KVDEBUG("preparing %s", left);
int rc =
sqlite3_prepare_v2(k->db,
left, -1,
&stmt, &left);
if (rc)
{
KVDEBUG("prepare failed");
_rollback(k);
return false;
}
/* Ok, we've got prepared stmt. Let her rip. */
if (!_kvdb_run_stmt(k, stmt))
{
_rollback(k);
return false;
}
}
KVDEBUG("upgrade succeeded");
stmt = _prep_stmt(k, "UPDATE db_state SET value=?1 WHERE key='version'");
schema++;
KVDEBUG("setting schema to %d", schema);
(void)sqlite3_bind_int(stmt, 1, schema);
bool rv = _kvdb_run_stmt(k, stmt);
if (rv)
_commit(k);
else
_rollback(k);
return rv;
}
ssize_t
Reader::_appendToTop ( Value && v )
{
//PWSHOWMETHOD();
if ( m_status.empty() )
{
m_cont.push(v);
return m_cont.size();
}
auto& top(m_status.top());
if ( not top.node.isArray() ) RETURN_READER_ERROR("last stack is not array");
top.node[top.index].assign(v);
++top.index;
if ( top.index == top.count ) return _rollback();
return m_cont.size();
}
void kvdb_destroy(kvdb k)
{
_rollback(k);
KVASSERT(k, "no object to kvdb_destroy");
if (k->oid_ih)
{
ihash_iterate(k->oid_ih, _ih_free_iterator, NULL);
ihash_destroy(k->oid_ih);
}
if (k->ss_app)
stringset_destroy(k->ss_app);
if (k->ss_class)
stringset_destroy(k->ss_class);
if (k->ss_key)
stringset_destroy(k->ss_key);
if (k->db)
sqlite3_close(k->db);
if (k->err)
free(k->err);
free(k);
}
void BackgroundSync::_produce(OperationContext* txn, executor::TaskExecutor* taskExecutor) {
// this oplog reader does not do a handshake because we don't want the server it's syncing
// from to track how far it has synced
{
stdx::unique_lock<stdx::mutex> lock(_mutex);
if (_lastOpTimeFetched.isNull()) {
// then we're initial syncing and we're still waiting for this to be set
lock.unlock();
sleepsecs(1);
// if there is no one to sync from
return;
}
if (_replCoord->isWaitingForApplierToDrain() || _replCoord->getMemberState().primary() ||
inShutdownStrict()) {
return;
}
}
while (MONGO_FAIL_POINT(rsBgSyncProduce)) {
sleepmillis(0);
}
// find a target to sync from the last optime fetched
OpTime lastOpTimeFetched;
{
stdx::unique_lock<stdx::mutex> lock(_mutex);
lastOpTimeFetched = _lastOpTimeFetched;
_syncSourceHost = HostAndPort();
}
OplogReader syncSourceReader;
syncSourceReader.connectToSyncSource(txn, lastOpTimeFetched, _replCoord);
// no server found
if (syncSourceReader.getHost().empty()) {
sleepsecs(1);
// if there is no one to sync from
return;
}
long long lastHashFetched;
{
stdx::lock_guard<stdx::mutex> lock(_mutex);
if (_pause) {
return;
}
lastOpTimeFetched = _lastOpTimeFetched;
lastHashFetched = _lastFetchedHash;
_syncSourceHost = syncSourceReader.getHost();
_replCoord->signalUpstreamUpdater();
}
const Milliseconds oplogSocketTimeout(OplogReader::kSocketTimeout);
// Prefer host in oplog reader to _syncSourceHost because _syncSourceHost may be cleared
// if sync source feedback fails.
const HostAndPort source = syncSourceReader.getHost();
syncSourceReader.resetConnection();
// no more references to oplog reader from here on.
// If this status is not OK after the fetcher returns from wait(),
// proceed to execute rollback
Status remoteOplogStartStatus = Status::OK();
auto fetcherCallback = stdx::bind(&BackgroundSync::_fetcherCallback,
this,
stdx::placeholders::_1,
stdx::placeholders::_3,
stdx::cref(source),
lastOpTimeFetched,
lastHashFetched,
&remoteOplogStartStatus);
auto cmdObj = BSON("find" << nsToCollectionSubstring(rsOplogName) << "filter"
<< BSON("ts" << BSON("$gte" << lastOpTimeFetched.getTimestamp()))
<< "tailable" << true << "oplogReplay" << true << "awaitData" << true
<< "maxTimeMS" << int(fetcherMaxTimeMS.count()));
Fetcher fetcher(taskExecutor,
source,
nsToDatabase(rsOplogName),
cmdObj,
fetcherCallback,
rpc::makeEmptyMetadata());
auto scheduleStatus = fetcher.schedule();
if (!scheduleStatus.isOK()) {
warning() << "unable to schedule fetcher to read remote oplog on " << source << ": "
<< scheduleStatus;
return;
}
fetcher.wait();
// If the background sync is paused after the fetcher is started, we need to
// re-evaluate our sync source and oplog common point.
if (isPaused()) {
return;
}
// Execute rollback if necessary.
// Rollback is a synchronous operation that uses the task executor and may not be
// executed inside the fetcher callback.
if (!remoteOplogStartStatus.isOK()) {
const int messagingPortTags = 0;
ConnectionPool connectionPool(messagingPortTags);
std::unique_ptr<ConnectionPool::ConnectionPtr> connection;
auto getConnection =
[&connection, &connectionPool, oplogSocketTimeout, source]() -> DBClientBase* {
if (!connection.get()) {
connection.reset(new ConnectionPool::ConnectionPtr(
&connectionPool, source, Date_t::now(), oplogSocketTimeout));
};
return connection->get();
};
log() << "starting rollback: " << remoteOplogStartStatus;
_rollback(txn, source, getConnection);
stop();
}
}
void BackgroundSync::_produce(OperationContext* txn) {
while (MONGO_FAIL_POINT(pauseRsBgSyncProducer)) {
sleepmillis(0);
}
// this oplog reader does not do a handshake because we don't want the server it's syncing
// from to track how far it has synced
{
stdx::unique_lock<stdx::mutex> lock(_mutex);
if (_lastOpTimeFetched.isNull()) {
// then we're initial syncing and we're still waiting for this to be set
lock.unlock();
sleepsecs(1);
// if there is no one to sync from
return;
}
if (!_replCoord->isCatchingUp() &&
(_replCoord->isWaitingForApplierToDrain() || _replCoord->getMemberState().primary())) {
return;
}
if (_inShutdown_inlock()) {
return;
}
}
// find a target to sync from the last optime fetched
OpTime lastOpTimeFetched;
HostAndPort source;
SyncSourceResolverResponse syncSourceResp;
SyncSourceResolver* syncSourceResolver;
OpTime minValid;
if (_replCoord->getMemberState().recovering()) {
auto minValidSaved = StorageInterface::get(txn)->getMinValid(txn);
if (minValidSaved > lastOpTimeFetched) {
minValid = minValidSaved;
}
}
{
stdx::unique_lock<stdx::mutex> lock(_mutex);
lastOpTimeFetched = _lastOpTimeFetched;
_syncSourceHost = HostAndPort();
_syncSourceResolver = stdx::make_unique<SyncSourceResolver>(
_replicationCoordinatorExternalState->getTaskExecutor(),
_replCoord,
lastOpTimeFetched,
minValid,
[&syncSourceResp](const SyncSourceResolverResponse& resp) { syncSourceResp = resp; });
syncSourceResolver = _syncSourceResolver.get();
}
// This may deadlock if called inside the mutex because SyncSourceResolver::startup() calls
// ReplicationCoordinator::chooseNewSyncSource(). ReplicationCoordinatorImpl's mutex has to
// acquired before BackgroundSync's.
// It is safe to call startup() outside the mutex on this instance of SyncSourceResolver because
// we do not destroy this instance outside of this function.
auto status = _syncSourceResolver->startup();
if (ErrorCodes::CallbackCanceled == status || ErrorCodes::isShutdownError(status.code())) {
return;
}
fassertStatusOK(40349, status);
syncSourceResolver->join();
syncSourceResolver = nullptr;
{
stdx::unique_lock<stdx::mutex> lock(_mutex);
_syncSourceResolver.reset();
}
if (syncSourceResp.syncSourceStatus == ErrorCodes::OplogStartMissing) {
// All (accessible) sync sources were too stale.
if (_replCoord->isCatchingUp()) {
warning() << "Too stale to catch up.";
log() << "Our newest OpTime : " << lastOpTimeFetched;
log() << "Earliest OpTime available is " << syncSourceResp.earliestOpTimeSeen
<< " from " << syncSourceResp.getSyncSource();
sleepsecs(1);
return;
}
error() << "too stale to catch up -- entering maintenance mode";
log() << "Our newest OpTime : " << lastOpTimeFetched;
log() << "Earliest OpTime available is " << syncSourceResp.earliestOpTimeSeen;
log() << "See http://dochub.mongodb.org/core/resyncingaverystalereplicasetmember";
auto status = _replCoord->setMaintenanceMode(true);
if (!status.isOK()) {
warning() << "Failed to transition into maintenance mode: " << status;
}
bool worked = _replCoord->setFollowerMode(MemberState::RS_RECOVERING);
if (!worked) {
warning() << "Failed to transition into " << MemberState(MemberState::RS_RECOVERING)
<< ". Current state: " << _replCoord->getMemberState();
}
return;
} else if (syncSourceResp.isOK() && !syncSourceResp.getSyncSource().empty()) {
stdx::lock_guard<stdx::mutex> lock(_mutex);
_syncSourceHost = syncSourceResp.getSyncSource();
source = _syncSourceHost;
} else {
if (!syncSourceResp.isOK()) {
log() << "failed to find sync source, received error "
<< syncSourceResp.syncSourceStatus.getStatus();
}
// No sync source found.
sleepsecs(1);
return;
}
long long lastHashFetched;
{
stdx::lock_guard<stdx::mutex> lock(_mutex);
if (_stopped) {
return;
}
lastOpTimeFetched = _lastOpTimeFetched;
lastHashFetched = _lastFetchedHash;
if (!_replCoord->isCatchingUp()) {
_replCoord->signalUpstreamUpdater();
}
}
// Set the applied point if unset. This is most likely the first time we've established a sync
// source since stepping down or otherwise clearing the applied point. We need to set this here,
// before the OplogWriter gets a chance to append to the oplog.
if (StorageInterface::get(txn)->getAppliedThrough(txn).isNull()) {
StorageInterface::get(txn)->setAppliedThrough(txn, _replCoord->getMyLastAppliedOpTime());
}
// "lastFetched" not used. Already set in _enqueueDocuments.
Status fetcherReturnStatus = Status::OK();
DataReplicatorExternalStateBackgroundSync dataReplicatorExternalState(
_replCoord, _replicationCoordinatorExternalState, this);
OplogFetcher* oplogFetcher;
try {
auto executor = _replicationCoordinatorExternalState->getTaskExecutor();
auto config = _replCoord->getConfig();
auto onOplogFetcherShutdownCallbackFn =
[&fetcherReturnStatus](const Status& status, const OpTimeWithHash& lastFetched) {
fetcherReturnStatus = status;
};
stdx::lock_guard<stdx::mutex> lock(_mutex);
_oplogFetcher = stdx::make_unique<OplogFetcher>(
executor,
OpTimeWithHash(lastHashFetched, lastOpTimeFetched),
source,
NamespaceString(rsOplogName),
config,
_replicationCoordinatorExternalState->getOplogFetcherMaxFetcherRestarts(),
&dataReplicatorExternalState,
stdx::bind(&BackgroundSync::_enqueueDocuments,
this,
stdx::placeholders::_1,
stdx::placeholders::_2,
stdx::placeholders::_3),
onOplogFetcherShutdownCallbackFn);
oplogFetcher = _oplogFetcher.get();
} catch (const mongo::DBException& ex) {
fassertFailedWithStatus(34440, exceptionToStatus());
}
LOG(1) << "scheduling fetcher to read remote oplog on " << _syncSourceHost << " starting at "
<< oplogFetcher->getCommandObject_forTest()["filter"];
auto scheduleStatus = oplogFetcher->startup();
if (!scheduleStatus.isOK()) {
warning() << "unable to schedule fetcher to read remote oplog on " << source << ": "
<< scheduleStatus;
return;
}
oplogFetcher->join();
LOG(1) << "fetcher stopped reading remote oplog on " << source;
// If the background sync is stopped after the fetcher is started, we need to
// re-evaluate our sync source and oplog common point.
if (isStopped()) {
return;
}
if (fetcherReturnStatus.code() == ErrorCodes::OplogOutOfOrder) {
// This is bad because it means that our source
// has not returned oplog entries in ascending ts order, and they need to be.
warning() << redact(fetcherReturnStatus);
// Do not blacklist the server here, it will be blacklisted when we try to reuse it,
// if it can't return a matching oplog start from the last fetch oplog ts field.
return;
} else if (fetcherReturnStatus.code() == ErrorCodes::OplogStartMissing ||
fetcherReturnStatus.code() == ErrorCodes::RemoteOplogStale) {
if (_replCoord->isCatchingUp()) {
warning() << "Rollback situation detected in catch-up mode; catch-up mode will end.";
sleepsecs(1);
return;
}
// Rollback is a synchronous operation that uses the task executor and may not be
// executed inside the fetcher callback.
const int messagingPortTags = 0;
ConnectionPool connectionPool(messagingPortTags);
std::unique_ptr<ConnectionPool::ConnectionPtr> connection;
auto getConnection = [&connection, &connectionPool, source]() -> DBClientBase* {
if (!connection.get()) {
connection.reset(new ConnectionPool::ConnectionPtr(
&connectionPool, source, Date_t::now(), kRollbackOplogSocketTimeout));
};
return connection->get();
};
{
stdx::lock_guard<stdx::mutex> lock(_mutex);
lastOpTimeFetched = _lastOpTimeFetched;
}
log() << "Starting rollback due to " << redact(fetcherReturnStatus);
// Wait till all buffered oplog entries have drained and been applied.
auto lastApplied = _replCoord->getMyLastAppliedOpTime();
if (lastApplied != lastOpTimeFetched) {
log() << "Waiting for all operations from " << lastApplied << " until "
<< lastOpTimeFetched << " to be applied before starting rollback.";
while (lastOpTimeFetched > (lastApplied = _replCoord->getMyLastAppliedOpTime())) {
sleepmillis(10);
if (isStopped() || inShutdown()) {
return;
}
}
}
// check that we are at minvalid, otherwise we cannot roll back as we may be in an
// inconsistent state
const auto minValid = StorageInterface::get(txn)->getMinValid(txn);
if (lastApplied < minValid) {
fassertNoTrace(18750,
Status(ErrorCodes::UnrecoverableRollbackError,
str::stream() << "need to rollback, but in inconsistent state. "
<< "minvalid: "
<< minValid.toString()
<< " > our last optime: "
<< lastApplied.toString()));
}
_rollback(txn, source, getConnection);
stop();
} else if (fetcherReturnStatus == ErrorCodes::InvalidBSON) {
Seconds blacklistDuration(60);
warning() << "Fetcher got invalid BSON while querying oplog. Blacklisting sync source "
<< source << " for " << blacklistDuration << ".";
_replCoord->blacklistSyncSource(source, Date_t::now() + blacklistDuration);
} else if (!fetcherReturnStatus.isOK()) {
warning() << "Fetcher stopped querying remote oplog with error: "
<< redact(fetcherReturnStatus);
}
}
void BackgroundSync::_produce(OperationContext* txn) {
// this oplog reader does not do a handshake because we don't want the server it's syncing
// from to track how far it has synced
{
stdx::unique_lock<stdx::mutex> lock(_mutex);
if (_lastOpTimeFetched.isNull()) {
// then we're initial syncing and we're still waiting for this to be set
lock.unlock();
sleepsecs(1);
// if there is no one to sync from
return;
}
if (_replCoord->isWaitingForApplierToDrain() || _replCoord->getMemberState().primary() ||
inShutdownStrict()) {
return;
}
}
while (MONGO_FAIL_POINT(rsBgSyncProduce)) {
sleepmillis(0);
}
// find a target to sync from the last optime fetched
OpTime lastOpTimeFetched;
HostAndPort source;
{
stdx::unique_lock<stdx::mutex> lock(_mutex);
lastOpTimeFetched = _lastOpTimeFetched;
_syncSourceHost = HostAndPort();
}
SyncSourceResolverResponse syncSourceResp =
_syncSourceResolver.findSyncSource(txn, lastOpTimeFetched);
if (syncSourceResp.syncSourceStatus == ErrorCodes::OplogStartMissing) {
// All (accessible) sync sources were too stale.
error() << "too stale to catch up -- entering maintenance mode";
log() << "Our newest OpTime : " << lastOpTimeFetched;
log() << "Earliest OpTime available is " << syncSourceResp.earliestOpTimeSeen;
log() << "See http://dochub.mongodb.org/core/resyncingaverystalereplicasetmember";
setMinValid(txn, {lastOpTimeFetched, syncSourceResp.earliestOpTimeSeen});
auto status = _replCoord->setMaintenanceMode(true);
if (!status.isOK()) {
warning() << "Failed to transition into maintenance mode.";
}
bool worked = _replCoord->setFollowerMode(MemberState::RS_RECOVERING);
if (!worked) {
warning() << "Failed to transition into " << MemberState(MemberState::RS_RECOVERING)
<< ". Current state: " << _replCoord->getMemberState();
}
return;
} else if (syncSourceResp.isOK() && !syncSourceResp.getSyncSource().empty()) {
stdx::lock_guard<stdx::mutex> lock(_mutex);
_syncSourceHost = syncSourceResp.getSyncSource();
source = _syncSourceHost;
} else {
if (!syncSourceResp.isOK()) {
log() << "failed to find sync source, received error "
<< syncSourceResp.syncSourceStatus.getStatus();
}
// No sync source found.
sleepsecs(1);
return;
}
long long lastHashFetched;
{
stdx::lock_guard<stdx::mutex> lock(_mutex);
if (_stopped) {
return;
}
lastOpTimeFetched = _lastOpTimeFetched;
lastHashFetched = _lastFetchedHash;
_replCoord->signalUpstreamUpdater();
}
const auto isV1ElectionProtocol = _replCoord->isV1ElectionProtocol();
// Under protocol version 1, make the awaitData timeout (maxTimeMS) dependent on the election
// timeout. This enables the sync source to communicate liveness of the primary to secondaries.
// Under protocol version 0, use a default timeout of 2 seconds for awaitData.
const Milliseconds fetcherMaxTimeMS(
isV1ElectionProtocol ? _replCoord->getConfig().getElectionTimeoutPeriod() / 2 : Seconds(2));
Status fetcherReturnStatus = Status::OK();
auto fetcherCallback = stdx::bind(&BackgroundSync::_fetcherCallback,
this,
stdx::placeholders::_1,
stdx::placeholders::_3,
stdx::cref(source),
lastOpTimeFetched,
lastHashFetched,
fetcherMaxTimeMS,
&fetcherReturnStatus);
BSONObjBuilder cmdBob;
cmdBob.append("find", nsToCollectionSubstring(rsOplogName));
cmdBob.append("filter", BSON("ts" << BSON("$gte" << lastOpTimeFetched.getTimestamp())));
cmdBob.append("tailable", true);
cmdBob.append("oplogReplay", true);
cmdBob.append("awaitData", true);
cmdBob.append("maxTimeMS", durationCount<Milliseconds>(Minutes(1))); // 1 min initial find.
BSONObjBuilder metadataBob;
if (isV1ElectionProtocol) {
cmdBob.append("term", _replCoord->getTerm());
metadataBob.append(rpc::kReplSetMetadataFieldName, 1);
}
auto dbName = nsToDatabase(rsOplogName);
auto cmdObj = cmdBob.obj();
auto metadataObj = metadataBob.obj();
Fetcher fetcher(&_threadPoolTaskExecutor,
source,
dbName,
cmdObj,
fetcherCallback,
metadataObj,
_replCoord->getConfig().getElectionTimeoutPeriod());
LOG(1) << "scheduling fetcher to read remote oplog on " << source << " starting at "
<< cmdObj["filter"];
auto scheduleStatus = fetcher.schedule();
if (!scheduleStatus.isOK()) {
warning() << "unable to schedule fetcher to read remote oplog on " << source << ": "
<< scheduleStatus;
return;
}
fetcher.wait();
LOG(1) << "fetcher stopped reading remote oplog on " << source;
// If the background sync is stopped after the fetcher is started, we need to
// re-evaluate our sync source and oplog common point.
if (isStopped()) {
return;
}
if (fetcherReturnStatus.code() == ErrorCodes::OplogOutOfOrder) {
// This is bad because it means that our source
// has not returned oplog entries in ascending ts order, and they need to be.
warning() << fetcherReturnStatus.toString();
// Do not blacklist the server here, it will be blacklisted when we try to reuse it,
// if it can't return a matching oplog start from the last fetch oplog ts field.
return;
} else if (fetcherReturnStatus.code() == ErrorCodes::OplogStartMissing ||
fetcherReturnStatus.code() == ErrorCodes::RemoteOplogStale) {
// Rollback is a synchronous operation that uses the task executor and may not be
// executed inside the fetcher callback.
const int messagingPortTags = 0;
ConnectionPool connectionPool(messagingPortTags);
std::unique_ptr<ConnectionPool::ConnectionPtr> connection;
auto getConnection = [&connection, &connectionPool, source]() -> DBClientBase* {
if (!connection.get()) {
connection.reset(new ConnectionPool::ConnectionPtr(
&connectionPool, source, Date_t::now(), oplogSocketTimeout));
};
return connection->get();
};
{
stdx::lock_guard<stdx::mutex> lock(_mutex);
lastOpTimeFetched = _lastOpTimeFetched;
}
log() << "Starting rollback due to " << fetcherReturnStatus;
// Wait till all buffered oplog entries have drained and been applied.
auto lastApplied = _replCoord->getMyLastAppliedOpTime();
if (lastApplied != lastOpTimeFetched) {
log() << "Waiting for all operations from " << lastApplied << " until "
<< lastOpTimeFetched << " to be applied before starting rollback.";
while (lastOpTimeFetched > (lastApplied = _replCoord->getMyLastAppliedOpTime())) {
sleepmillis(10);
if (isStopped() || inShutdown()) {
return;
}
}
}
// check that we are at minvalid, otherwise we cannot roll back as we may be in an
// inconsistent state
BatchBoundaries boundaries = getMinValid(txn);
if (!boundaries.start.isNull() || boundaries.end > lastApplied) {
fassertNoTrace(18750,
Status(ErrorCodes::UnrecoverableRollbackError,
str::stream()
<< "need to rollback, but in inconsistent state. "
<< "minvalid: " << boundaries.end.toString()
<< " > our last optime: " << lastApplied.toString()));
}
_rollback(txn, source, getConnection);
stop();
} else if (fetcherReturnStatus == ErrorCodes::InvalidBSON) {
Seconds blacklistDuration(60);
warning() << "Fetcher got invalid BSON while querying oplog. Blacklisting sync source "
<< source << " for " << blacklistDuration << ".";
_replCoord->blacklistSyncSource(source, Date_t::now() + blacklistDuration);
} else if (!fetcherReturnStatus.isOK()) {
warning() << "Fetcher error querying oplog: " << fetcherReturnStatus.toString();
}
}
void BackgroundSync::_produce(OperationContext* txn) {
// this oplog reader does not do a handshake because we don't want the server it's syncing
// from to track how far it has synced
{
stdx::unique_lock<stdx::mutex> lock(_mutex);
if (_lastOpTimeFetched.isNull()) {
// then we're initial syncing and we're still waiting for this to be set
lock.unlock();
sleepsecs(1);
// if there is no one to sync from
return;
}
if (_replCoord->isWaitingForApplierToDrain() || _replCoord->getMemberState().primary() ||
inShutdownStrict()) {
return;
}
}
while (MONGO_FAIL_POINT(rsBgSyncProduce)) {
sleepmillis(0);
}
// find a target to sync from the last optime fetched
OpTime lastOpTimeFetched;
{
stdx::unique_lock<stdx::mutex> lock(_mutex);
lastOpTimeFetched = _lastOpTimeFetched;
_syncSourceHost = HostAndPort();
}
OplogReader syncSourceReader;
syncSourceReader.connectToSyncSource(txn, lastOpTimeFetched, _replCoord);
// no server found
if (syncSourceReader.getHost().empty()) {
sleepsecs(1);
// if there is no one to sync from
return;
}
long long lastHashFetched;
{
stdx::lock_guard<stdx::mutex> lock(_mutex);
if (_pause) {
return;
}
lastOpTimeFetched = _lastOpTimeFetched;
lastHashFetched = _lastFetchedHash;
_syncSourceHost = syncSourceReader.getHost();
_replCoord->signalUpstreamUpdater();
}
const Milliseconds oplogSocketTimeout(OplogReader::kSocketTimeout);
const auto isV1ElectionProtocol = _replCoord->isV1ElectionProtocol();
// Under protocol version 1, make the awaitData timeout (maxTimeMS) dependent on the election
// timeout. This enables the sync source to communicate liveness of the primary to secondaries.
// Under protocol version 0, use a default timeout of 2 seconds for awaitData.
const Milliseconds fetcherMaxTimeMS(
isV1ElectionProtocol ? _replCoord->getConfig().getElectionTimeoutPeriod() / 2 : Seconds(2));
// Prefer host in oplog reader to _syncSourceHost because _syncSourceHost may be cleared
// if sync source feedback fails.
const HostAndPort source = syncSourceReader.getHost();
syncSourceReader.resetConnection();
// no more references to oplog reader from here on.
Status fetcherReturnStatus = Status::OK();
auto fetcherCallback = stdx::bind(&BackgroundSync::_fetcherCallback,
this,
stdx::placeholders::_1,
stdx::placeholders::_3,
stdx::cref(source),
lastOpTimeFetched,
lastHashFetched,
fetcherMaxTimeMS,
&fetcherReturnStatus);
BSONObjBuilder cmdBob;
cmdBob.append("find", nsToCollectionSubstring(rsOplogName));
cmdBob.append("filter", BSON("ts" << BSON("$gte" << lastOpTimeFetched.getTimestamp())));
cmdBob.append("tailable", true);
cmdBob.append("oplogReplay", true);
cmdBob.append("awaitData", true);
cmdBob.append("maxTimeMS", durationCount<Milliseconds>(fetcherMaxTimeMS));
BSONObjBuilder metadataBob;
if (isV1ElectionProtocol) {
cmdBob.append("term", _replCoord->getTerm());
metadataBob.append(rpc::kReplSetMetadataFieldName, 1);
}
auto dbName = nsToDatabase(rsOplogName);
auto cmdObj = cmdBob.obj();
auto metadataObj = metadataBob.obj();
Fetcher fetcher(&_threadPoolTaskExecutor,
source,
dbName,
cmdObj,
fetcherCallback,
metadataObj,
_replCoord->getConfig().getElectionTimeoutPeriod());
LOG(1) << "scheduling fetcher to read remote oplog on " << source << " starting at "
<< cmdObj["filter"];
auto scheduleStatus = fetcher.schedule();
if (!scheduleStatus.isOK()) {
warning() << "unable to schedule fetcher to read remote oplog on " << source << ": "
<< scheduleStatus;
return;
}
fetcher.wait();
LOG(1) << "fetcher stopped reading remote oplog on " << source;
// If the background sync is paused after the fetcher is started, we need to
// re-evaluate our sync source and oplog common point.
if (isPaused()) {
return;
}
if (fetcherReturnStatus.code() == ErrorCodes::OplogOutOfOrder) {
// This is bad because it means that our source
// has not returned oplog entries in ascending ts order, and they need to be.
warning() << fetcherReturnStatus.toString();
// Do not blacklist the server here, it will be blacklisted when we try to reuse it,
// if it can't return a matching oplog start from the last fetch oplog ts field.
return;
} else if (fetcherReturnStatus.code() == ErrorCodes::OplogStartMissing ||
fetcherReturnStatus.code() == ErrorCodes::RemoteOplogStale) {
// Rollback is a synchronous operation that uses the task executor and may not be
// executed inside the fetcher callback.
const int messagingPortTags = 0;
ConnectionPool connectionPool(messagingPortTags);
std::unique_ptr<ConnectionPool::ConnectionPtr> connection;
auto getConnection =
[&connection, &connectionPool, oplogSocketTimeout, source]() -> DBClientBase* {
if (!connection.get()) {
connection.reset(new ConnectionPool::ConnectionPtr(
&connectionPool, source, Date_t::now(), oplogSocketTimeout));
};
return connection->get();
};
log() << "starting rollback: " << fetcherReturnStatus;
_rollback(txn, source, getConnection);
stop();
} else if (!fetcherReturnStatus.isOK()) {
warning() << "Fetcher error querying oplog: " << fetcherReturnStatus.toString();
}
}
