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/**
* Copyright (C) 2012 10gen 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::kReplication
#include "mongo/platform/basic.h"
#include "mongo/db/repl/bgsync.h"
#include "mongo/base/counter.h"
#include "mongo/db/auth/authorization_session.h"
#include "mongo/db/client.h"
#include "mongo/db/commands/fsync.h"
#include "mongo/db/commands/server_status_metric.h"
#include "mongo/db/dbhelpers.h"
#include "mongo/db/operation_context_impl.h"
#include "mongo/db/repl/oplog.h"
#include "mongo/db/repl/replication_coordinator_global.h"
#include "mongo/db/repl/replication_coordinator_impl.h"
#include "mongo/db/repl/rs_rollback.h"
#include "mongo/db/repl/rs_sync.h"
#include "mongo/db/stats/timer_stats.h"
#include "mongo/util/exit.h"
#include "mongo/util/fail_point_service.h"
#include "mongo/util/log.h"
namespace mongo {
namespace repl {
namespace {
const char hashFieldName[] = "h";
int SleepToAllowBatchingMillis = 2;
const int BatchIsSmallish = 40000; // bytes
} // namespace
MONGO_FP_DECLARE(rsBgSyncProduce);
BackgroundSync* BackgroundSync::s_instance = 0;
boost::mutex BackgroundSync::s_mutex;
//The number and time spent reading batches off the network
static TimerStats getmoreReplStats;
static ServerStatusMetricField<TimerStats> displayBatchesRecieved(
"repl.network.getmores",
&getmoreReplStats );
//The oplog entries read via the oplog reader
static Counter64 opsReadStats;
static ServerStatusMetricField<Counter64> displayOpsRead( "repl.network.ops",
&opsReadStats );
//The bytes read via the oplog reader
static Counter64 networkByteStats;
static ServerStatusMetricField<Counter64> displayBytesRead( "repl.network.bytes",
&networkByteStats );
//The count of items in the buffer
static Counter64 bufferCountGauge;
static ServerStatusMetricField<Counter64> displayBufferCount( "repl.buffer.count",
&bufferCountGauge );
//The size (bytes) of items in the buffer
static Counter64 bufferSizeGauge;
static ServerStatusMetricField<Counter64> displayBufferSize( "repl.buffer.sizeBytes",
&bufferSizeGauge );
//The max size (bytes) of the buffer
static int bufferMaxSizeGauge = 256*1024*1024;
static ServerStatusMetricField<int> displayBufferMaxSize( "repl.buffer.maxSizeBytes",
&bufferMaxSizeGauge );
BackgroundSyncInterface::~BackgroundSyncInterface() {}
size_t getSize(const BSONObj& o) {
// SERVER-9808 Avoid Fortify complaint about implicit signed->unsigned conversion
return static_cast<size_t>(o.objsize());
}
BackgroundSync::BackgroundSync() : _buffer(bufferMaxSizeGauge, &getSize),
_lastOpTimeFetched(std::numeric_limits<int>::max(),
0),
_lastAppliedHash(0),
_lastFetchedHash(0),
_pause(true),
_appliedBuffer(true),
_replCoord(getGlobalReplicationCoordinator()),
_initialSyncRequestedFlag(false),
_indexPrefetchConfig(PREFETCH_ALL) {
}
BackgroundSync* BackgroundSync::get() {
boost::unique_lock<boost::mutex> lock(s_mutex);
if (s_instance == NULL && !inShutdown()) {
s_instance = new BackgroundSync();
}
return s_instance;
}
void BackgroundSync::shutdown() {
boost::lock_guard<boost::mutex> lock(_mutex);
// Clear the buffer in case the producerThread is waiting in push() due to a full queue.
_buffer.clear();
// Wake up producerThread so it notices that we're in shutdown
_condvar.notify_all();
}
void BackgroundSync::notify(OperationContext* txn) {
boost::lock_guard<boost::mutex> lock(_mutex);
// If all ops in the buffer have been applied, unblock waitForRepl (if it's waiting)
if (_buffer.empty()) {
_appliedBuffer = true;
_replCoord->signalDrainComplete(txn);
_condvar.notify_all();
}
}
void BackgroundSync::producerThread() {
Client::initThread("rsBackgroundSync");
cc().getAuthorizationSession()->grantInternalAuthorization();
while (!inShutdown()) {
try {
_producerThread();
}
catch (const DBException& e) {
std::string msg(str::stream() << "sync producer problem: " << e.toString());
error() << msg;
_replCoord->setMyHeartbeatMessage(msg);
}
catch (const std::exception& e2) {
severe() << "sync producer exception: " << e2.what();
fassertFailed(28546);
}
}
cc().shutdown();
}
void BackgroundSync::_producerThread() {
const MemberState state = _replCoord->getMemberState();
// we want to pause when the state changes to primary
if (_replCoord->isWaitingForApplierToDrain() || state.primary()) {
if (!_pause) {
stop();
}
sleepsecs(1);
return;
}
// TODO(spencer): Use a condition variable to await loading a config.
if (state.startup()) {
// Wait for a config to be loaded
sleepsecs(1);
return;
}
OperationContextImpl txn;
// We need to wait until initial sync has started.
if (_replCoord->getMyLastOptime().isNull()) {
sleepsecs(1);
return;
}
// we want to unpause when we're no longer primary
// start() also loads _lastOpTimeFetched, which we know is set from the "if"
else if (_pause) {
start(&txn);
}
produce(&txn);
}
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
{
boost::unique_lock<boost::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;
}
// Wait until we've applied the ops we have before we choose a sync target
while (!_appliedBuffer && !inShutdownStrict()) {
_condvar.wait(lock);
}
if (inShutdownStrict()) {
return;
}
}
while (MONGO_FAIL_POINT(rsBgSyncProduce)) {
sleepmillis(0);
}
// find a target to sync from the last optime fetched
OpTime lastOpTimeFetched;
{
boost::unique_lock<boost::mutex> lock(_mutex);
lastOpTimeFetched = _lastOpTimeFetched;
_syncSourceHost = HostAndPort();
}
_syncSourceReader.resetConnection();
_syncSourceReader.connectToSyncSource(txn, lastOpTimeFetched, _replCoord);
{
boost::unique_lock<boost::mutex> lock(_mutex);
// no server found
if (_syncSourceReader.getHost().empty()) {
lock.unlock();
sleepsecs(1);
// if there is no one to sync from
return;
}
lastOpTimeFetched = _lastOpTimeFetched;
_syncSourceHost = _syncSourceReader.getHost();
_replCoord->signalUpstreamUpdater();
}
_syncSourceReader.tailingQueryGTE(rsoplog, lastOpTimeFetched);
// if target cut connections between connecting and querying (for
// example, because it stepped down) we might not have a cursor
if (!_syncSourceReader.haveCursor()) {
return;
}
if (_rollbackIfNeeded(txn, _syncSourceReader)) {
stop();
return;
}
while (!inShutdown()) {
if (!_syncSourceReader.moreInCurrentBatch()) {
// Check some things periodically
// (whenever we run out of items in the
// current cursor batch)
int bs = _syncSourceReader.currentBatchMessageSize();
if( bs > 0 && bs < BatchIsSmallish ) {
// on a very low latency network, if we don't wait a little, we'll be
// getting ops to write almost one at a time. this will both be expensive
// for the upstream server as well as potentially defeating our parallel
// application of batches on the secondary.
//
// the inference here is basically if the batch is really small, we are
// "caught up".
//
sleepmillis(SleepToAllowBatchingMillis);
}
// If we are transitioning to primary state, we need to leave
// this loop in order to go into bgsync-pause mode.
if (_replCoord->isWaitingForApplierToDrain() ||
_replCoord->getMemberState().primary()) {
return;
}
// re-evaluate quality of sync target
if (shouldChangeSyncSource()) {
return;
}
{
//record time for each getmore
TimerHolder batchTimer(&getmoreReplStats);
// This calls receiveMore() on the oplogreader cursor.
// It can wait up to five seconds for more data.
_syncSourceReader.more();
}
networkByteStats.increment(_syncSourceReader.currentBatchMessageSize());
if (!_syncSourceReader.moreInCurrentBatch()) {
// If there is still no data from upstream, check a few more things
// and then loop back for another pass at getting more data
{
boost::unique_lock<boost::mutex> lock(_mutex);
if (_pause) {
return;
}
}
_syncSourceReader.tailCheck();
if( !_syncSourceReader.haveCursor() ) {
LOG(1) << "replSet end syncTail pass";
return;
}
continue;
}
}
// If we are transitioning to primary state, we need to leave
// this loop in order to go into bgsync-pause mode.
if (_replCoord->isWaitingForApplierToDrain() ||
_replCoord->getMemberState().primary()) {
LOG(1) << "waiting for draining or we are primary, not adding more ops to buffer";
return;
}
// At this point, we are guaranteed to have at least one thing to read out
// of the oplogreader cursor.
BSONObj o = _syncSourceReader.nextSafe().getOwned();
opsReadStats.increment();
{
boost::unique_lock<boost::mutex> lock(_mutex);
_appliedBuffer = false;
}
OCCASIONALLY {
LOG(2) << "bgsync buffer has " << _buffer.size() << " bytes";
}
bufferCountGauge.increment();
bufferSizeGauge.increment(getSize(o));
_buffer.push(o);
{
boost::unique_lock<boost::mutex> lock(_mutex);
_lastFetchedHash = o["h"].numberLong();
_lastOpTimeFetched = o["ts"]._opTime();
LOG(3) << "replSet lastOpTimeFetched: " << _lastOpTimeFetched.toStringPretty();
}
}
}
bool BackgroundSync::shouldChangeSyncSource() {
// is it even still around?
if (getSyncTarget().empty() || _syncSourceReader.getHost().empty()) {
return true;
}
// check other members: is any member's optime more than MaxSyncSourceLag seconds
// ahead of the current sync source?
return _replCoord->shouldChangeSyncSource(_syncSourceReader.getHost());
}
bool BackgroundSync::peek(BSONObj* op) {
return _buffer.peek(*op);
}
void BackgroundSync::waitForMore() {
BSONObj op;
// Block for one second before timing out.
// Ignore the value of the op we peeked at.
_buffer.blockingPeek(op, 1);
}
void BackgroundSync::consume() {
// this is just to get the op off the queue, it's been peeked at
// and queued for application already
BSONObj op = _buffer.blockingPop();
bufferCountGauge.decrement(1);
bufferSizeGauge.decrement(getSize(op));
}
bool BackgroundSync::_rollbackIfNeeded(OperationContext* txn, OplogReader& r) {
string hn = r.conn()->getServerAddress();
if (!r.more()) {
try {
BSONObj theirLastOp = r.getLastOp(rsoplog);
if (theirLastOp.isEmpty()) {
log() << "replSet error empty query result from " << hn << " oplog";
sleepsecs(2);
return true;
}
OpTime theirTS = theirLastOp["ts"]._opTime();
if (theirTS < _lastOpTimeFetched) {
log() << "replSet we are ahead of the sync source, will try to roll back";
syncRollback(txn, _replCoord->getMyLastOptime(), &r, _replCoord);
return true;
}
/* we're not ahead? maybe our new query got fresher data. best to come back and try again */
log() << "replSet syncTail condition 1";
sleepsecs(1);
}
catch(DBException& e) {
log() << "replSet error querying " << hn << ' ' << e.toString();
sleepsecs(2);
}
return true;
}
BSONObj o = r.nextSafe();
OpTime ts = o["ts"]._opTime();
long long hash = o["h"].numberLong();
if( ts != _lastOpTimeFetched || hash != _lastFetchedHash ) {
log() << "replSet our last op time fetched: " << _lastOpTimeFetched.toStringPretty();
log() << "replset source's GTE: " << ts.toStringPretty();
syncRollback(txn, _replCoord->getMyLastOptime(), &r, _replCoord);
return true;
}
return false;
}
HostAndPort BackgroundSync::getSyncTarget() {
boost::unique_lock<boost::mutex> lock(_mutex);
return _syncSourceHost;
}
void BackgroundSync::clearSyncTarget() {
boost::unique_lock<boost::mutex> lock(_mutex);
_syncSourceHost = HostAndPort();
}
void BackgroundSync::stop() {
boost::unique_lock<boost::mutex> lock(_mutex);
_pause = true;
_syncSourceHost = HostAndPort();
_lastOpTimeFetched = OpTime(0,0);
_lastFetchedHash = 0;
_condvar.notify_all();
}
void BackgroundSync::start(OperationContext* txn) {
massert(16235, "going to start syncing, but buffer is not empty", _buffer.empty());
long long updatedLastAppliedHash = _readLastAppliedHash(txn);
boost::lock_guard<boost::mutex> lk(_mutex);
_pause = false;
// reset _last fields with current oplog data
_lastAppliedHash = updatedLastAppliedHash;
_lastOpTimeFetched = _replCoord->getMyLastOptime();
_lastFetchedHash = _lastAppliedHash;
LOG(1) << "replset bgsync fetch queue set to: " << _lastOpTimeFetched <<
" " << _lastFetchedHash;
}
long long BackgroundSync::getLastAppliedHash() const {
boost::lock_guard<boost::mutex> lck(_mutex);
return _lastAppliedHash;
}
void BackgroundSync::setLastAppliedHash(long long newHash) {
boost::lock_guard<boost::mutex> lck(_mutex);
_lastAppliedHash = newHash;
}
void BackgroundSync::loadLastAppliedHash(OperationContext* txn) {
long long result = _readLastAppliedHash(txn);
boost::lock_guard<boost::mutex> lk(_mutex);
_lastAppliedHash = result;
}
long long BackgroundSync::_readLastAppliedHash(OperationContext* txn) {
BSONObj oplogEntry;
try {
ScopedTransaction transaction(txn, MODE_IX);
Lock::DBLock lk(txn->lockState(), "local", MODE_X);
bool success = Helpers::getLast(txn, rsoplog, oplogEntry);
if (!success) {
// This can happen when we are to do an initial sync. lastHash will be set
// after the initial sync is complete.
return 0;
}
}
catch (const DBException& ex) {
severe() << "Problem reading " << rsoplog << ": " << ex.toStatus();
fassertFailed(18904);
}
BSONElement hashElement = oplogEntry[hashFieldName];
if (hashElement.eoo()) {
severe() << "Most recent entry in " << rsoplog << " missing \"" << hashFieldName <<
"\" field";
fassertFailed(18902);
}
if (hashElement.type() != NumberLong) {
severe() << "Expected type of \"" << hashFieldName << "\" in most recent " <<
rsoplog << " entry to have type NumberLong, but found " <<
typeName(hashElement.type());
fassertFailed(18903);
}
return hashElement.safeNumberLong();
}
bool BackgroundSync::getInitialSyncRequestedFlag() {
boost::lock_guard<boost::mutex> lock(_initialSyncMutex);
return _initialSyncRequestedFlag;
}
void BackgroundSync::setInitialSyncRequestedFlag(bool value) {
boost::lock_guard<boost::mutex> lock(_initialSyncMutex);
_initialSyncRequestedFlag = value;
}
} // namespace repl
} // namespace mongo
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