318 lines
7.9 KiB
PHP
318 lines
7.9 KiB
PHP
<?php
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/**
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* @defgroup JobQueue JobQueue
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*/
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if ( !defined( 'MEDIAWIKI' ) ) {
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die( "This file is part of MediaWiki, it is not a valid entry point\n" );
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}
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/**
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* Class to both describe a background job and handle jobs.
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*
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* @ingroup JobQueue
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*/
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abstract class Job {
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var $command,
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$title,
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$params,
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$id,
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$removeDuplicates,
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$error;
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/*-------------------------------------------------------------------------
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* Abstract functions
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*------------------------------------------------------------------------*/
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/**
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* Run the job
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* @return boolean success
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*/
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abstract function run();
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/*-------------------------------------------------------------------------
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* Static functions
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*------------------------------------------------------------------------*/
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/**
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* @deprecated use LinksUpdate::queueRecursiveJobs()
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*/
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/**
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* static function queueLinksJobs( $titles ) {}
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*/
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/**
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* Pop a job of a certain type. This tries less hard than pop() to
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* actually find a job; it may be adversely affected by concurrent job
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* runners.
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*/
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static function pop_type( $type ) {
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wfProfilein( __METHOD__ );
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$dbw = wfGetDB( DB_MASTER );
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$row = $dbw->selectRow(
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'job',
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'*',
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array( 'job_cmd' => $type ),
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__METHOD__,
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array( 'LIMIT' => 1 )
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);
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if ( $row === false ) {
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wfProfileOut( __METHOD__ );
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return false;
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}
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/* Ensure we "own" this row */
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$dbw->delete( 'job', array( 'job_id' => $row->job_id ), __METHOD__ );
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$affected = $dbw->affectedRows();
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if ( $affected == 0 ) {
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wfProfileOut( __METHOD__ );
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return false;
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}
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$namespace = $row->job_namespace;
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$dbkey = $row->job_title;
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$title = Title::makeTitleSafe( $namespace, $dbkey );
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$job = Job::factory( $row->job_cmd, $title, Job::extractBlob( $row->job_params ), $row->job_id );
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$dbw->delete( 'job', $job->insertFields(), __METHOD__ );
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$dbw->commit();
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wfProfileOut( __METHOD__ );
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return $job;
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}
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/**
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* Pop a job off the front of the queue
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*
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* @param $offset Integer: Number of jobs to skip
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* @return Job or false if there's no jobs
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*/
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static function pop( $offset = 0 ) {
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wfProfileIn( __METHOD__ );
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$dbr = wfGetDB( DB_SLAVE );
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/* Get a job from the slave, start with an offset,
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scan full set afterwards, avoid hitting purged rows
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NB: If random fetch previously was used, offset
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will always be ahead of few entries
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*/
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$row = $dbr->selectRow( 'job', '*', "job_id >= ${offset}", __METHOD__,
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array( 'ORDER BY' => 'job_id', 'LIMIT' => 1 ) );
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// Refetching without offset is needed as some of job IDs could have had delayed commits
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// and have lower IDs than jobs already executed, blame concurrency :)
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//
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if ( $row === false ) {
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if ( $offset != 0 ) {
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$row = $dbr->selectRow( 'job', '*', '', __METHOD__,
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array( 'ORDER BY' => 'job_id', 'LIMIT' => 1 ) );
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}
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if ( $row === false ) {
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wfProfileOut( __METHOD__ );
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return false;
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}
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}
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$offset = $row->job_id;
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// Try to delete it from the master
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$dbw = wfGetDB( DB_MASTER );
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$dbw->delete( 'job', array( 'job_id' => $row->job_id ), __METHOD__ );
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$affected = $dbw->affectedRows();
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$dbw->commit();
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if ( !$affected ) {
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// Failed, someone else beat us to it
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// Try getting a random row
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$row = $dbw->selectRow( 'job', array( 'MIN(job_id) as minjob',
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'MAX(job_id) as maxjob' ), '1=1', __METHOD__ );
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if ( $row === false || is_null( $row->minjob ) || is_null( $row->maxjob ) ) {
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// No jobs to get
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wfProfileOut( __METHOD__ );
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return false;
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}
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// Get the random row
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$row = $dbw->selectRow( 'job', '*',
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'job_id >= ' . mt_rand( $row->minjob, $row->maxjob ), __METHOD__ );
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if ( $row === false ) {
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// Random job gone before we got the chance to select it
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// Give up
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wfProfileOut( __METHOD__ );
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return false;
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}
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// Delete the random row
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$dbw->delete( 'job', array( 'job_id' => $row->job_id ), __METHOD__ );
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$affected = $dbw->affectedRows();
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$dbw->commit();
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if ( !$affected ) {
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// Random job gone before we exclusively deleted it
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// Give up
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wfProfileOut( __METHOD__ );
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return false;
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}
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}
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// If execution got to here, there's a row in $row that has been deleted from the database
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// by this thread. Hence the concurrent pop was successful.
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$namespace = $row->job_namespace;
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$dbkey = $row->job_title;
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$title = Title::makeTitleSafe( $namespace, $dbkey );
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$job = Job::factory( $row->job_cmd, $title, Job::extractBlob( $row->job_params ), $row->job_id );
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// Remove any duplicates it may have later in the queue
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// Deadlock prone section
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$dbw->begin();
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$dbw->delete( 'job', $job->insertFields(), __METHOD__ );
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$dbw->commit();
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wfProfileOut( __METHOD__ );
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return $job;
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}
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/**
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* Create the appropriate object to handle a specific job
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*
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* @param $command String: Job command
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* @param $title Title: Associated title
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* @param $params Array: Job parameters
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* @param $id Int: Job identifier
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* @return Job
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*/
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static function factory( $command, $title, $params = false, $id = 0 ) {
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global $wgJobClasses;
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if( isset( $wgJobClasses[$command] ) ) {
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$class = $wgJobClasses[$command];
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return new $class( $title, $params, $id );
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}
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throw new MWException( "Invalid job command `{$command}`" );
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}
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static function makeBlob( $params ) {
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if ( $params !== false ) {
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return serialize( $params );
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} else {
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return '';
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}
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}
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static function extractBlob( $blob ) {
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if ( (string)$blob !== '' ) {
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return unserialize( $blob );
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} else {
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return false;
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}
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}
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/**
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* Batch-insert a group of jobs into the queue.
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* This will be wrapped in a transaction with a forced commit.
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*
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* This may add duplicate at insert time, but they will be
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* removed later on, when the first one is popped.
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*
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* @param $jobs array of Job objects
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*/
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static function batchInsert( $jobs ) {
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if( !count( $jobs ) ) {
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return;
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}
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$dbw = wfGetDB( DB_MASTER );
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$rows = array();
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foreach( $jobs as $job ) {
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$rows[] = $job->insertFields();
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if ( count( $rows ) >= 50 ) {
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# Do a small transaction to avoid slave lag
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$dbw->begin();
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$dbw->insert( 'job', $rows, __METHOD__, 'IGNORE' );
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$dbw->commit();
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$rows = array();
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}
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}
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if ( $rows ) {
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$dbw->begin();
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$dbw->insert( 'job', $rows, __METHOD__, 'IGNORE' );
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$dbw->commit();
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}
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}
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/*-------------------------------------------------------------------------
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* Non-static functions
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*------------------------------------------------------------------------*/
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function __construct( $command, $title, $params = false, $id = 0 ) {
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$this->command = $command;
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$this->title = $title;
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$this->params = $params;
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$this->id = $id;
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// A bit of premature generalisation
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// Oh well, the whole class is premature generalisation really
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$this->removeDuplicates = true;
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}
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/**
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* Insert a single job into the queue.
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*/
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function insert() {
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$fields = $this->insertFields();
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$dbw = wfGetDB( DB_MASTER );
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if ( $this->removeDuplicates ) {
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$res = $dbw->select( 'job', array( '1' ), $fields, __METHOD__ );
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if ( $dbw->numRows( $res ) ) {
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return;
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}
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}
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$dbw->insert( 'job', $fields, __METHOD__ );
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}
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protected function insertFields() {
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$dbw = wfGetDB( DB_MASTER );
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return array(
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'job_id' => $dbw->nextSequenceValue( 'job_job_id_seq' ),
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'job_cmd' => $this->command,
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'job_namespace' => $this->title->getNamespace(),
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'job_title' => $this->title->getDBkey(),
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'job_params' => Job::makeBlob( $this->params )
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);
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}
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function toString() {
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$paramString = '';
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if ( $this->params ) {
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foreach ( $this->params as $key => $value ) {
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if ( $paramString != '' ) {
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$paramString .= ' ';
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}
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$paramString .= "$key=$value";
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}
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}
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if ( is_object( $this->title ) ) {
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$s = "{$this->command} " . $this->title->getPrefixedDBkey();
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if ( $paramString !== '' ) {
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$s .= ' ' . $paramString;
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}
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return $s;
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} else {
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return "{$this->command} $paramString";
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}
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}
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protected function setLastError( $error ) {
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$this->error = $error;
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}
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function getLastError() {
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return $this->error;
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}
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}
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