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Diffstat (limited to 'includes/job/JobQueueDB.php')
| -rw-r--r-- | includes/job/JobQueueDB.php | 716 |
1 files changed, 716 insertions, 0 deletions
diff --git a/includes/job/JobQueueDB.php b/includes/job/JobQueueDB.php new file mode 100644 index 00000000..ff7f7abc --- /dev/null +++ b/includes/job/JobQueueDB.php @@ -0,0 +1,716 @@ +<?php +/** + * Database-backed job queue code. + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * 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 General Public License for more details. + * + * You should have received a copy of the GNU General Public License along + * with this program; if not, write to the Free Software Foundation, Inc., + * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. + * http://www.gnu.org/copyleft/gpl.html + * + * @file + * @author Aaron Schulz + */ + +/** + * Class to handle job queues stored in the DB + * + * @ingroup JobQueue + * @since 1.21 + */ +class JobQueueDB extends JobQueue { + const ROOTJOB_TTL = 1209600; // integer; seconds to remember root jobs (14 days) + const CACHE_TTL_SHORT = 30; // integer; seconds to cache info without re-validating + const CACHE_TTL_LONG = 300; // integer; seconds to cache info that is kept up to date + const MAX_AGE_PRUNE = 604800; // integer; seconds a job can live once claimed + const MAX_JOB_RANDOM = 2147483647; // integer; 2^31 - 1, used for job_random + const MAX_OFFSET = 255; // integer; maximum number of rows to skip + + protected $cluster = false; // string; name of an external DB cluster + + /** + * Additional parameters include: + * - cluster : The name of an external cluster registered via LBFactory. + * If not specified, the primary DB cluster for the wiki will be used. + * This can be overridden with a custom cluster so that DB handles will + * be retrieved via LBFactory::getExternalLB() and getConnection(). + * @param $params array + */ + protected function __construct( array $params ) { + parent::__construct( $params ); + $this->cluster = isset( $params['cluster'] ) ? $params['cluster'] : false; + } + + protected function supportedOrders() { + return array( 'random', 'timestamp', 'fifo' ); + } + + protected function optimalOrder() { + return 'random'; + } + + /** + * @see JobQueue::doIsEmpty() + * @return bool + */ + protected function doIsEmpty() { + global $wgMemc; + + $key = $this->getCacheKey( 'empty' ); + + $isEmpty = $wgMemc->get( $key ); + if ( $isEmpty === 'true' ) { + return true; + } elseif ( $isEmpty === 'false' ) { + return false; + } + + list( $dbr, $scope ) = $this->getSlaveDB(); + $found = $dbr->selectField( // unclaimed job + 'job', '1', array( 'job_cmd' => $this->type, 'job_token' => '' ), __METHOD__ + ); + $wgMemc->add( $key, $found ? 'false' : 'true', self::CACHE_TTL_LONG ); + + return !$found; + } + + /** + * @see JobQueue::doGetSize() + * @return integer + */ + protected function doGetSize() { + global $wgMemc; + + $key = $this->getCacheKey( 'size' ); + + $size = $wgMemc->get( $key ); + if ( is_int( $size ) ) { + return $size; + } + + list( $dbr, $scope ) = $this->getSlaveDB(); + $size = (int)$dbr->selectField( 'job', 'COUNT(*)', + array( 'job_cmd' => $this->type, 'job_token' => '' ), + __METHOD__ + ); + $wgMemc->set( $key, $size, self::CACHE_TTL_SHORT ); + + return $size; + } + + /** + * @see JobQueue::doGetAcquiredCount() + * @return integer + */ + protected function doGetAcquiredCount() { + global $wgMemc; + + if ( $this->claimTTL <= 0 ) { + return 0; // no acknowledgements + } + + $key = $this->getCacheKey( 'acquiredcount' ); + + $count = $wgMemc->get( $key ); + if ( is_int( $count ) ) { + return $count; + } + + list( $dbr, $scope ) = $this->getSlaveDB(); + $count = (int)$dbr->selectField( 'job', 'COUNT(*)', + array( 'job_cmd' => $this->type, "job_token != {$dbr->addQuotes( '' )}" ), + __METHOD__ + ); + $wgMemc->set( $key, $count, self::CACHE_TTL_SHORT ); + + return $count; + } + + /** + * @see JobQueue::doBatchPush() + * @param array $jobs + * @param $flags + * @throws DBError|Exception + * @return bool + */ + protected function doBatchPush( array $jobs, $flags ) { + if ( count( $jobs ) ) { + list( $dbw, $scope ) = $this->getMasterDB(); + + $rowSet = array(); // (sha1 => job) map for jobs that are de-duplicated + $rowList = array(); // list of jobs for jobs that are are not de-duplicated + + foreach ( $jobs as $job ) { + $row = $this->insertFields( $job ); + if ( $job->ignoreDuplicates() ) { + $rowSet[$row['job_sha1']] = $row; + } else { + $rowList[] = $row; + } + } + + $key = $this->getCacheKey( 'empty' ); + $atomic = ( $flags & self::QoS_Atomic ); + + $dbw->onTransactionIdle( + function() use ( $dbw, $rowSet, $rowList, $atomic, $key, $scope + ) { + global $wgMemc; + + if ( $atomic ) { + $dbw->begin( __METHOD__ ); // wrap all the job additions in one transaction + } + try { + // Strip out any duplicate jobs that are already in the queue... + if ( count( $rowSet ) ) { + $res = $dbw->select( 'job', 'job_sha1', + array( + // No job_type condition since it's part of the job_sha1 hash + 'job_sha1' => array_keys( $rowSet ), + 'job_token' => '' // unclaimed + ), + __METHOD__ + ); + foreach ( $res as $row ) { + wfDebug( "Job with hash '{$row->job_sha1}' is a duplicate." ); + unset( $rowSet[$row->job_sha1] ); // already enqueued + } + } + // Build the full list of job rows to insert + $rows = array_merge( $rowList, array_values( $rowSet ) ); + // Insert the job rows in chunks to avoid slave lag... + foreach ( array_chunk( $rows, 50 ) as $rowBatch ) { + $dbw->insert( 'job', $rowBatch, __METHOD__ ); + } + wfIncrStats( 'job-insert', count( $rows ) ); + wfIncrStats( 'job-insert-duplicate', + count( $rowSet ) + count( $rowList ) - count( $rows ) ); + } catch ( DBError $e ) { + if ( $atomic ) { + $dbw->rollback( __METHOD__ ); + } + throw $e; + } + if ( $atomic ) { + $dbw->commit( __METHOD__ ); + } + + $wgMemc->set( $key, 'false', JobQueueDB::CACHE_TTL_LONG ); + } ); + } + + return true; + } + + /** + * @see JobQueue::doPop() + * @return Job|bool + */ + protected function doPop() { + global $wgMemc; + + if ( $wgMemc->get( $this->getCacheKey( 'empty' ) ) === 'true' ) { + return false; // queue is empty + } + + list( $dbw, $scope ) = $this->getMasterDB(); + $dbw->commit( __METHOD__, 'flush' ); // flush existing transaction + $autoTrx = $dbw->getFlag( DBO_TRX ); // get current setting + $dbw->clearFlag( DBO_TRX ); // make each query its own transaction + $scopedReset = new ScopedCallback( function() use ( $dbw, $autoTrx ) { + $dbw->setFlag( $autoTrx ? DBO_TRX : 0 ); // restore old setting + } ); + + $uuid = wfRandomString( 32 ); // pop attempt + $job = false; // job popped off + do { // retry when our row is invalid or deleted as a duplicate + // Try to reserve a row in the DB... + if ( in_array( $this->order, array( 'fifo', 'timestamp' ) ) ) { + $row = $this->claimOldest( $uuid ); + } else { // random first + $rand = mt_rand( 0, self::MAX_JOB_RANDOM ); // encourage concurrent UPDATEs + $gte = (bool)mt_rand( 0, 1 ); // find rows with rand before/after $rand + $row = $this->claimRandom( $uuid, $rand, $gte ); + } + // Check if we found a row to reserve... + if ( !$row ) { + $wgMemc->set( $this->getCacheKey( 'empty' ), 'true', self::CACHE_TTL_LONG ); + break; // nothing to do + } + wfIncrStats( 'job-pop' ); + // Get the job object from the row... + $title = Title::makeTitleSafe( $row->job_namespace, $row->job_title ); + if ( !$title ) { + $dbw->delete( 'job', array( 'job_id' => $row->job_id ), __METHOD__ ); + wfDebugLog( 'JobQueueDB', "Row has invalid title '{$row->job_title}'." ); + continue; // try again + } + $job = Job::factory( $row->job_cmd, $title, + self::extractBlob( $row->job_params ), $row->job_id ); + $job->id = $row->job_id; // XXX: work around broken subclasses + // Flag this job as an old duplicate based on its "root" job... + if ( $this->isRootJobOldDuplicate( $job ) ) { + wfIncrStats( 'job-pop-duplicate' ); + $job = DuplicateJob::newFromJob( $job ); // convert to a no-op + } + break; // done + } while( true ); + + return $job; + } + + /** + * Reserve a row with a single UPDATE without holding row locks over RTTs... + * + * @param string $uuid 32 char hex string + * @param $rand integer Random unsigned integer (31 bits) + * @param bool $gte Search for job_random >= $random (otherwise job_random <= $random) + * @return Row|false + */ + protected function claimRandom( $uuid, $rand, $gte ) { + global $wgMemc; + + list( $dbw, $scope ) = $this->getMasterDB(); + // Check cache to see if the queue has <= OFFSET items + $tinyQueue = $wgMemc->get( $this->getCacheKey( 'small' ) ); + + $row = false; // the row acquired + $invertedDirection = false; // whether one job_random direction was already scanned + // This uses a replication safe method for acquiring jobs. One could use UPDATE+LIMIT + // instead, but that either uses ORDER BY (in which case it deadlocks in MySQL) or is + // not replication safe. Due to http://bugs.mysql.com/bug.php?id=6980, subqueries cannot + // be used here with MySQL. + do { + if ( $tinyQueue ) { // queue has <= MAX_OFFSET rows + // For small queues, using OFFSET will overshoot and return no rows more often. + // Instead, this uses job_random to pick a row (possibly checking both directions). + $ineq = $gte ? '>=' : '<='; + $dir = $gte ? 'ASC' : 'DESC'; + $row = $dbw->selectRow( 'job', '*', // find a random job + array( + 'job_cmd' => $this->type, + 'job_token' => '', // unclaimed + "job_random {$ineq} {$dbw->addQuotes( $rand )}" ), + __METHOD__, + array( 'ORDER BY' => "job_random {$dir}" ) + ); + if ( !$row && !$invertedDirection ) { + $gte = !$gte; + $invertedDirection = true; + continue; // try the other direction + } + } else { // table *may* have >= MAX_OFFSET rows + // Bug 42614: "ORDER BY job_random" with a job_random inequality causes high CPU + // in MySQL if there are many rows for some reason. This uses a small OFFSET + // instead of job_random for reducing excess claim retries. + $row = $dbw->selectRow( 'job', '*', // find a random job + array( + 'job_cmd' => $this->type, + 'job_token' => '', // unclaimed + ), + __METHOD__, + array( 'OFFSET' => mt_rand( 0, self::MAX_OFFSET ) ) + ); + if ( !$row ) { + $tinyQueue = true; // we know the queue must have <= MAX_OFFSET rows + $wgMemc->set( $this->getCacheKey( 'small' ), 1, 30 ); + continue; // use job_random + } + } + if ( $row ) { // claim the job + $dbw->update( 'job', // update by PK + array( + 'job_token' => $uuid, + 'job_token_timestamp' => $dbw->timestamp(), + 'job_attempts = job_attempts+1' ), + array( 'job_cmd' => $this->type, 'job_id' => $row->job_id, 'job_token' => '' ), + __METHOD__ + ); + // This might get raced out by another runner when claiming the previously + // selected row. The use of job_random should minimize this problem, however. + if ( !$dbw->affectedRows() ) { + $row = false; // raced out + } + } else { + break; // nothing to do + } + } while ( !$row ); + + return $row; + } + + /** + * Reserve a row with a single UPDATE without holding row locks over RTTs... + * + * @param string $uuid 32 char hex string + * @return Row|false + */ + protected function claimOldest( $uuid ) { + list( $dbw, $scope ) = $this->getMasterDB(); + + $row = false; // the row acquired + do { + if ( $dbw->getType() === 'mysql' ) { + // Per http://bugs.mysql.com/bug.php?id=6980, we can't use subqueries on the + // same table being changed in an UPDATE query in MySQL (gives Error: 1093). + // Oracle and Postgre have no such limitation. However, MySQL offers an + // alternative here by supporting ORDER BY + LIMIT for UPDATE queries. + $dbw->query( "UPDATE {$dbw->tableName( 'job' )} " . + "SET " . + "job_token = {$dbw->addQuotes( $uuid ) }, " . + "job_token_timestamp = {$dbw->addQuotes( $dbw->timestamp() )}, " . + "job_attempts = job_attempts+1 " . + "WHERE ( " . + "job_cmd = {$dbw->addQuotes( $this->type )} " . + "AND job_token = {$dbw->addQuotes( '' )} " . + ") ORDER BY job_id ASC LIMIT 1", + __METHOD__ + ); + } else { + // Use a subquery to find the job, within an UPDATE to claim it. + // This uses as much of the DB wrapper functions as possible. + $dbw->update( 'job', + array( + 'job_token' => $uuid, + 'job_token_timestamp' => $dbw->timestamp(), + 'job_attempts = job_attempts+1' ), + array( 'job_id = (' . + $dbw->selectSQLText( 'job', 'job_id', + array( 'job_cmd' => $this->type, 'job_token' => '' ), + __METHOD__, + array( 'ORDER BY' => 'job_id ASC', 'LIMIT' => 1 ) ) . + ')' + ), + __METHOD__ + ); + } + // Fetch any row that we just reserved... + if ( $dbw->affectedRows() ) { + $row = $dbw->selectRow( 'job', '*', + array( 'job_cmd' => $this->type, 'job_token' => $uuid ), __METHOD__ + ); + if ( !$row ) { // raced out by duplicate job removal + wfDebugLog( 'JobQueueDB', "Row deleted as duplicate by another process." ); + } + } else { + break; // nothing to do + } + } while ( !$row ); + + return $row; + } + + /** + * Recycle or destroy any jobs that have been claimed for too long + * + * @return integer Number of jobs recycled/deleted + */ + public function recycleAndDeleteStaleJobs() { + global $wgMemc; + + $now = time(); + list( $dbw, $scope ) = $this->getMasterDB(); + $count = 0; // affected rows + + if ( !$dbw->lock( "jobqueue-recycle-{$this->type}", __METHOD__, 1 ) ) { + return $count; // already in progress + } + + // Remove claims on jobs acquired for too long if enabled... + if ( $this->claimTTL > 0 ) { + $claimCutoff = $dbw->timestamp( $now - $this->claimTTL ); + // Get the IDs of jobs that have be claimed but not finished after too long. + // These jobs can be recycled into the queue by expiring the claim. Selecting + // the IDs first means that the UPDATE can be done by primary key (less deadlocks). + $res = $dbw->select( 'job', 'job_id', + array( + 'job_cmd' => $this->type, + "job_token != {$dbw->addQuotes( '' )}", // was acquired + "job_token_timestamp < {$dbw->addQuotes( $claimCutoff )}", // stale + "job_attempts < {$dbw->addQuotes( $this->maxTries )}" ), // retries left + __METHOD__ + ); + $ids = array_map( function( $o ) { return $o->job_id; }, iterator_to_array( $res ) ); + if ( count( $ids ) ) { + // Reset job_token for these jobs so that other runners will pick them up. + // Set the timestamp to the current time, as it is useful to now that the job + // was already tried before (the timestamp becomes the "released" time). + $dbw->update( 'job', + array( + 'job_token' => '', + 'job_token_timestamp' => $dbw->timestamp( $now ) ), // time of release + array( + 'job_id' => $ids ), + __METHOD__ + ); + $count += $dbw->affectedRows(); + wfIncrStats( 'job-recycle', $dbw->affectedRows() ); + $wgMemc->set( $this->getCacheKey( 'empty' ), 'false', self::CACHE_TTL_LONG ); + } + } + + // Just destroy any stale jobs... + $pruneCutoff = $dbw->timestamp( $now - self::MAX_AGE_PRUNE ); + $conds = array( + 'job_cmd' => $this->type, + "job_token != {$dbw->addQuotes( '' )}", // was acquired + "job_token_timestamp < {$dbw->addQuotes( $pruneCutoff )}" // stale + ); + if ( $this->claimTTL > 0 ) { // only prune jobs attempted too many times... + $conds[] = "job_attempts >= {$dbw->addQuotes( $this->maxTries )}"; + } + // Get the IDs of jobs that are considered stale and should be removed. Selecting + // the IDs first means that the UPDATE can be done by primary key (less deadlocks). + $res = $dbw->select( 'job', 'job_id', $conds, __METHOD__ ); + $ids = array_map( function( $o ) { return $o->job_id; }, iterator_to_array( $res ) ); + if ( count( $ids ) ) { + $dbw->delete( 'job', array( 'job_id' => $ids ), __METHOD__ ); + $count += $dbw->affectedRows(); + } + + $dbw->unlock( "jobqueue-recycle-{$this->type}", __METHOD__ ); + + return $count; + } + + /** + * @see JobQueue::doAck() + * @param Job $job + * @throws MWException + * @return Job|bool + */ + protected function doAck( Job $job ) { + if ( !$job->getId() ) { + throw new MWException( "Job of type '{$job->getType()}' has no ID." ); + } + + list( $dbw, $scope ) = $this->getMasterDB(); + $dbw->commit( __METHOD__, 'flush' ); // flush existing transaction + $autoTrx = $dbw->getFlag( DBO_TRX ); // get current setting + $dbw->clearFlag( DBO_TRX ); // make each query its own transaction + $scopedReset = new ScopedCallback( function() use ( $dbw, $autoTrx ) { + $dbw->setFlag( $autoTrx ? DBO_TRX : 0 ); // restore old setting + } ); + + // Delete a row with a single DELETE without holding row locks over RTTs... + $dbw->delete( 'job', + array( 'job_cmd' => $this->type, 'job_id' => $job->getId() ), __METHOD__ ); + + return true; + } + + /** + * @see JobQueue::doDeduplicateRootJob() + * @param Job $job + * @throws MWException + * @return bool + */ + protected function doDeduplicateRootJob( Job $job ) { + $params = $job->getParams(); + if ( !isset( $params['rootJobSignature'] ) ) { + throw new MWException( "Cannot register root job; missing 'rootJobSignature'." ); + } elseif ( !isset( $params['rootJobTimestamp'] ) ) { + throw new MWException( "Cannot register root job; missing 'rootJobTimestamp'." ); + } + $key = $this->getRootJobCacheKey( $params['rootJobSignature'] ); + // Callers should call batchInsert() and then this function so that if the insert + // fails, the de-duplication registration will be aborted. Since the insert is + // deferred till "transaction idle", do the same here, so that the ordering is + // maintained. Having only the de-duplication registration succeed would cause + // jobs to become no-ops without any actual jobs that made them redundant. + list( $dbw, $scope ) = $this->getMasterDB(); + $dbw->onTransactionIdle( function() use ( $params, $key, $scope ) { + global $wgMemc; + + $timestamp = $wgMemc->get( $key ); // current last timestamp of this job + if ( $timestamp && $timestamp >= $params['rootJobTimestamp'] ) { + return true; // a newer version of this root job was enqueued + } + + // Update the timestamp of the last root job started at the location... + return $wgMemc->set( $key, $params['rootJobTimestamp'], JobQueueDB::ROOTJOB_TTL ); + } ); + + return true; + } + + /** + * Check if the "root" job of a given job has been superseded by a newer one + * + * @param $job Job + * @return bool + */ + protected function isRootJobOldDuplicate( Job $job ) { + global $wgMemc; + + $params = $job->getParams(); + if ( !isset( $params['rootJobSignature'] ) ) { + return false; // job has no de-deplication info + } elseif ( !isset( $params['rootJobTimestamp'] ) ) { + trigger_error( "Cannot check root job; missing 'rootJobTimestamp'." ); + return false; + } + + // Get the last time this root job was enqueued + $timestamp = $wgMemc->get( $this->getRootJobCacheKey( $params['rootJobSignature'] ) ); + + // Check if a new root job was started at the location after this one's... + return ( $timestamp && $timestamp > $params['rootJobTimestamp'] ); + } + + /** + * @see JobQueue::doWaitForBackups() + * @return void + */ + protected function doWaitForBackups() { + wfWaitForSlaves(); + } + + /** + * @return Array + */ + protected function doGetPeriodicTasks() { + return array( + 'recycleAndDeleteStaleJobs' => array( + 'callback' => array( $this, 'recycleAndDeleteStaleJobs' ), + 'period' => ceil( $this->claimTTL / 2 ) + ) + ); + } + + /** + * @return void + */ + protected function doFlushCaches() { + global $wgMemc; + + foreach ( array( 'empty', 'size', 'acquiredcount' ) as $type ) { + $wgMemc->delete( $this->getCacheKey( $type ) ); + } + } + + /** + * @see JobQueue::getAllQueuedJobs() + * @return Iterator + */ + public function getAllQueuedJobs() { + list( $dbr, $scope ) = $this->getSlaveDB(); + return new MappedIterator( + $dbr->select( 'job', '*', array( 'job_cmd' => $this->getType(), 'job_token' => '' ) ), + function( $row ) use ( $scope ) { + $job = Job::factory( + $row->job_cmd, + Title::makeTitle( $row->job_namespace, $row->job_title ), + strlen( $row->job_params ) ? unserialize( $row->job_params ) : false, + $row->job_id + ); + $job->id = $row->job_id; // XXX: work around broken subclasses + return $job; + } + ); + } + + /** + * @return Array (DatabaseBase, ScopedCallback) + */ + protected function getSlaveDB() { + return $this->getDB( DB_SLAVE ); + } + + /** + * @return Array (DatabaseBase, ScopedCallback) + */ + protected function getMasterDB() { + return $this->getDB( DB_MASTER ); + } + + /** + * @param $index integer (DB_SLAVE/DB_MASTER) + * @return Array (DatabaseBase, ScopedCallback) + */ + protected function getDB( $index ) { + $lb = ( $this->cluster !== false ) + ? wfGetLBFactory()->getExternalLB( $this->cluster, $this->wiki ) + : wfGetLB( $this->wiki ); + $conn = $lb->getConnection( $index, array(), $this->wiki ); + return array( + $conn, + new ScopedCallback( function() use ( $lb, $conn ) { + $lb->reuseConnection( $conn ); + } ) + ); + } + + /** + * @param $job Job + * @return array + */ + protected function insertFields( Job $job ) { + list( $dbw, $scope ) = $this->getMasterDB(); + return array( + // Fields that describe the nature of the job + 'job_cmd' => $job->getType(), + 'job_namespace' => $job->getTitle()->getNamespace(), + 'job_title' => $job->getTitle()->getDBkey(), + 'job_params' => self::makeBlob( $job->getParams() ), + // Additional job metadata + 'job_id' => $dbw->nextSequenceValue( 'job_job_id_seq' ), + 'job_timestamp' => $dbw->timestamp(), + 'job_sha1' => wfBaseConvert( + sha1( serialize( $job->getDeduplicationInfo() ) ), + 16, 36, 31 + ), + 'job_random' => mt_rand( 0, self::MAX_JOB_RANDOM ) + ); + } + + /** + * @return string + */ + private function getCacheKey( $property ) { + list( $db, $prefix ) = wfSplitWikiID( $this->wiki ); + return wfForeignMemcKey( $db, $prefix, 'jobqueue', $this->type, $property ); + } + + /** + * @param string $signature Hash identifier of the root job + * @return string + */ + private function getRootJobCacheKey( $signature ) { + list( $db, $prefix ) = wfSplitWikiID( $this->wiki ); + return wfForeignMemcKey( $db, $prefix, 'jobqueue', $this->type, 'rootjob', $signature ); + } + + /** + * @param $params + * @return string + */ + protected static function makeBlob( $params ) { + if ( $params !== false ) { + return serialize( $params ); + } else { + return ''; + } + } + + /** + * @param $blob + * @return bool|mixed + */ + protected static function extractBlob( $blob ) { + if ( (string)$blob !== '' ) { + return unserialize( $blob ); + } else { + return false; + } + } +} |