From 9db190c7e736ec8d063187d4241b59feaf7dc2d1 Mon Sep 17 00:00:00 2001 From: Pierre Schmitz Date: Wed, 22 Jun 2011 11:28:20 +0200 Subject: update to MediaWiki 1.17.0 --- includes/job/JobQueue.php | 344 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 344 insertions(+) create mode 100644 includes/job/JobQueue.php (limited to 'includes/job/JobQueue.php') diff --git a/includes/job/JobQueue.php b/includes/job/JobQueue.php new file mode 100644 index 00000000..8eec8215 --- /dev/null +++ b/includes/job/JobQueue.php @@ -0,0 +1,344 @@ +selectRow( + 'job', + '*', + array( 'job_cmd' => $type ), + __METHOD__, + array( 'LIMIT' => 1 ) + ); + + if ( $row === false ) { + wfProfileOut( __METHOD__ ); + return false; + } + + /* Ensure we "own" this row */ + $dbw->delete( 'job', array( 'job_id' => $row->job_id ), __METHOD__ ); + $affected = $dbw->affectedRows(); + + if ( $affected == 0 ) { + wfProfileOut( __METHOD__ ); + return false; + } + + $namespace = $row->job_namespace; + $dbkey = $row->job_title; + $title = Title::makeTitleSafe( $namespace, $dbkey ); + $job = Job::factory( $row->job_cmd, $title, Job::extractBlob( $row->job_params ), + $row->job_id ); + + $dbw->delete( 'job', $job->insertFields(), __METHOD__ ); + $dbw->commit(); + + wfProfileOut( __METHOD__ ); + return $job; + } + + /** + * Pop a job off the front of the queue + * + * @param $offset Integer: Number of jobs to skip + * @return Job or false if there's no jobs + */ + static function pop( $offset = 0 ) { + wfProfileIn( __METHOD__ ); + + $dbr = wfGetDB( DB_SLAVE ); + + /* Get a job from the slave, start with an offset, + scan full set afterwards, avoid hitting purged rows + + NB: If random fetch previously was used, offset + will always be ahead of few entries + */ + + $row = $dbr->selectRow( 'job', '*', "job_id >= ${offset}", __METHOD__, + array( 'ORDER BY' => 'job_id', 'LIMIT' => 1 ) ); + + // Refetching without offset is needed as some of job IDs could have had delayed commits + // and have lower IDs than jobs already executed, blame concurrency :) + // + if ( $row === false ) { + if ( $offset != 0 ) { + $row = $dbr->selectRow( 'job', '*', '', __METHOD__, + array( 'ORDER BY' => 'job_id', 'LIMIT' => 1 ) ); + } + + if ( $row === false ) { + wfProfileOut( __METHOD__ ); + return false; + } + } + + // Try to delete it from the master + $dbw = wfGetDB( DB_MASTER ); + $dbw->delete( 'job', array( 'job_id' => $row->job_id ), __METHOD__ ); + $affected = $dbw->affectedRows(); + $dbw->commit(); + + if ( !$affected ) { + // Failed, someone else beat us to it + // Try getting a random row + $row = $dbw->selectRow( 'job', array( 'MIN(job_id) as minjob', + 'MAX(job_id) as maxjob' ), '1=1', __METHOD__ ); + if ( $row === false || is_null( $row->minjob ) || is_null( $row->maxjob ) ) { + // No jobs to get + wfProfileOut( __METHOD__ ); + return false; + } + // Get the random row + $row = $dbw->selectRow( 'job', '*', + 'job_id >= ' . mt_rand( $row->minjob, $row->maxjob ), __METHOD__ ); + if ( $row === false ) { + // Random job gone before we got the chance to select it + // Give up + wfProfileOut( __METHOD__ ); + return false; + } + // Delete the random row + $dbw->delete( 'job', array( 'job_id' => $row->job_id ), __METHOD__ ); + $affected = $dbw->affectedRows(); + $dbw->commit(); + + if ( !$affected ) { + // Random job gone before we exclusively deleted it + // Give up + wfProfileOut( __METHOD__ ); + return false; + } + } + + // If execution got to here, there's a row in $row that has been deleted from the database + // by this thread. Hence the concurrent pop was successful. + $namespace = $row->job_namespace; + $dbkey = $row->job_title; + $title = Title::makeTitleSafe( $namespace, $dbkey ); + $job = Job::factory( $row->job_cmd, $title, Job::extractBlob( $row->job_params ), $row->job_id ); + + // Remove any duplicates it may have later in the queue + // Deadlock prone section + $dbw->begin(); + $dbw->delete( 'job', $job->insertFields(), __METHOD__ ); + $dbw->commit(); + + wfProfileOut( __METHOD__ ); + return $job; + } + + /** + * Create the appropriate object to handle a specific job + * + * @param $command String: Job command + * @param $title Title: Associated title + * @param $params Array: Job parameters + * @param $id Int: Job identifier + * @return Job + */ + static function factory( $command, $title, $params = false, $id = 0 ) { + global $wgJobClasses; + if( isset( $wgJobClasses[$command] ) ) { + $class = $wgJobClasses[$command]; + return new $class( $title, $params, $id ); + } + throw new MWException( "Invalid job command `{$command}`" ); + } + + static function makeBlob( $params ) { + if ( $params !== false ) { + return serialize( $params ); + } else { + return ''; + } + } + + static function extractBlob( $blob ) { + if ( (string)$blob !== '' ) { + return unserialize( $blob ); + } else { + return false; + } + } + + /** + * Batch-insert a group of jobs into the queue. + * This will be wrapped in a transaction with a forced commit. + * + * This may add duplicate at insert time, but they will be + * removed later on, when the first one is popped. + * + * @param $jobs array of Job objects + */ + static function batchInsert( $jobs ) { + if ( !count( $jobs ) ) { + return; + } + $dbw = wfGetDB( DB_MASTER ); + $rows = array(); + foreach ( $jobs as $job ) { + $rows[] = $job->insertFields(); + if ( count( $rows ) >= 50 ) { + # Do a small transaction to avoid slave lag + $dbw->begin(); + $dbw->insert( 'job', $rows, __METHOD__, 'IGNORE' ); + $dbw->commit(); + $rows = array(); + } + } + if ( $rows ) { // last chunk + $dbw->begin(); + $dbw->insert( 'job', $rows, __METHOD__, 'IGNORE' ); + $dbw->commit(); + } + wfIncrStats( 'job-insert', count( $jobs ) ); + } + + /** + * Insert a group of jobs into the queue. + * + * Same as batchInsert() but does not commit and can thus + * be rolled-back as part of a larger transaction. However, + * large batches of jobs can cause slave lag. + * + * @param $jobs array of Job objects + */ + static function safeBatchInsert( $jobs ) { + if ( !count( $jobs ) ) { + return; + } + $dbw = wfGetDB( DB_MASTER ); + $rows = array(); + foreach ( $jobs as $job ) { + $rows[] = $job->insertFields(); + if ( count( $rows ) >= 500 ) { + $dbw->insert( 'job', $rows, __METHOD__, 'IGNORE' ); + $rows = array(); + } + } + if ( $rows ) { // last chunk + $dbw->insert( 'job', $rows, __METHOD__, 'IGNORE' ); + } + wfIncrStats( 'job-insert', count( $jobs ) ); + } + + /*------------------------------------------------------------------------- + * Non-static functions + *------------------------------------------------------------------------*/ + + function __construct( $command, $title, $params = false, $id = 0 ) { + $this->command = $command; + $this->title = $title; + $this->params = $params; + $this->id = $id; + + // A bit of premature generalisation + // Oh well, the whole class is premature generalisation really + $this->removeDuplicates = true; + } + + /** + * Insert a single job into the queue. + * @return bool true on success + */ + function insert() { + $fields = $this->insertFields(); + + $dbw = wfGetDB( DB_MASTER ); + + if ( $this->removeDuplicates ) { + $res = $dbw->select( 'job', array( '1' ), $fields, __METHOD__ ); + if ( $dbw->numRows( $res ) ) { + return; + } + } + return $dbw->insert( 'job', $fields, __METHOD__ ); + } + + protected function insertFields() { + $dbw = wfGetDB( DB_MASTER ); + return array( + 'job_id' => $dbw->nextSequenceValue( 'job_job_id_seq' ), + 'job_cmd' => $this->command, + 'job_namespace' => $this->title->getNamespace(), + 'job_title' => $this->title->getDBkey(), + 'job_params' => Job::makeBlob( $this->params ) + ); + } + + function toString() { + $paramString = ''; + if ( $this->params ) { + foreach ( $this->params as $key => $value ) { + if ( $paramString != '' ) { + $paramString .= ' '; + } + $paramString .= "$key=$value"; + } + } + + if ( is_object( $this->title ) ) { + $s = "{$this->command} " . $this->title->getPrefixedDBkey(); + if ( $paramString !== '' ) { + $s .= ' ' . $paramString; + } + return $s; + } else { + return "{$this->command} $paramString"; + } + } + + protected function setLastError( $error ) { + $this->error = $error; + } + + function getLastError() { + return $this->error; + } +} -- cgit v1.2.3-54-g00ecf