6 * @defgroup JobQueue JobQueue
9 if ( !defined( 'MEDIAWIKI' ) ) {
10 die( "This file is part of MediaWiki, it is not a valid entry point\n" );
14 * Class to both describe a background job and handle jobs.
31 /*-------------------------------------------------------------------------
33 *------------------------------------------------------------------------*/
37 * @return boolean success
39 abstract function run();
41 /*-------------------------------------------------------------------------
43 *------------------------------------------------------------------------*/
46 * Pop a job of a certain type. This tries less hard than pop() to
47 * actually find a job; it may be adversely affected by concurrent job
54 static function pop_type( $type ) {
55 wfProfilein( __METHOD__
);
57 $dbw = wfGetDB( DB_MASTER
);
61 $row = $dbw->selectRow(
64 array( 'job_cmd' => $type ),
66 array( 'LIMIT' => 1, 'FOR UPDATE' )
69 if ( $row === false ) {
71 wfProfileOut( __METHOD__
);
75 /* Ensure we "own" this row */
76 $dbw->delete( 'job', array( 'job_id' => $row->job_id
), __METHOD__
);
77 $affected = $dbw->affectedRows();
80 if ( $affected == 0 ) {
81 wfProfileOut( __METHOD__
);
85 wfIncrStats( 'job-pop' );
86 $namespace = $row->job_namespace
;
87 $dbkey = $row->job_title
;
88 $title = Title
::makeTitleSafe( $namespace, $dbkey );
89 $job = Job
::factory( $row->job_cmd
, $title, Job
::extractBlob( $row->job_params
),
92 $job->removeDuplicates();
94 wfProfileOut( __METHOD__
);
99 * Pop a job off the front of the queue
101 * @param $offset Integer: Number of jobs to skip
102 * @return Job or false if there's no jobs
104 static function pop( $offset = 0 ) {
105 global $wgJobTypesExcludedFromDefaultQueue;
106 wfProfileIn( __METHOD__
);
108 $dbr = wfGetDB( DB_SLAVE
);
110 /* Get a job from the slave, start with an offset,
111 scan full set afterwards, avoid hitting purged rows
113 NB: If random fetch previously was used, offset
114 will always be ahead of few entries
116 $conditions = array();
117 if ( count( $wgJobTypesExcludedFromDefaultQueue ) != 0 ) {
118 foreach ( $wgJobTypesExcludedFromDefaultQueue as $cmdType ) {
119 $conditions[] = "job_cmd != " . $dbr->addQuotes( $cmdType );
122 $offset = intval( $offset );
123 $options = array( 'ORDER BY' => 'job_id', 'USE INDEX' => 'PRIMARY' );
125 $row = $dbr->selectRow( 'job', '*',
126 array_merge( $conditions, array( "job_id >= $offset" ) ),
131 // Refetching without offset is needed as some of job IDs could have had delayed commits
132 // and have lower IDs than jobs already executed, blame concurrency :)
134 if ( $row === false ) {
135 if ( $offset != 0 ) {
136 $row = $dbr->selectRow( 'job', '*', $conditions, __METHOD__
, $options );
139 if ( $row === false ) {
140 wfProfileOut( __METHOD__
);
145 // Try to delete it from the master
146 $dbw = wfGetDB( DB_MASTER
);
147 $dbw->delete( 'job', array( 'job_id' => $row->job_id
), __METHOD__
);
148 $affected = $dbw->affectedRows();
152 // Failed, someone else beat us to it
153 // Try getting a random row
154 $row = $dbw->selectRow( 'job', array( 'MIN(job_id) as minjob',
155 'MAX(job_id) as maxjob' ), '1=1', __METHOD__
);
156 if ( $row === false ||
is_null( $row->minjob
) ||
is_null( $row->maxjob
) ) {
158 wfProfileOut( __METHOD__
);
161 // Get the random row
162 $row = $dbw->selectRow( 'job', '*',
163 'job_id >= ' . mt_rand( $row->minjob
, $row->maxjob
), __METHOD__
);
164 if ( $row === false ) {
165 // Random job gone before we got the chance to select it
167 wfProfileOut( __METHOD__
);
170 // Delete the random row
171 $dbw->delete( 'job', array( 'job_id' => $row->job_id
), __METHOD__
);
172 $affected = $dbw->affectedRows();
176 // Random job gone before we exclusively deleted it
178 wfProfileOut( __METHOD__
);
183 // If execution got to here, there's a row in $row that has been deleted from the database
184 // by this thread. Hence the concurrent pop was successful.
185 wfIncrStats( 'job-pop' );
186 $namespace = $row->job_namespace
;
187 $dbkey = $row->job_title
;
188 $title = Title
::makeTitleSafe( $namespace, $dbkey );
189 $job = Job
::factory( $row->job_cmd
, $title, Job
::extractBlob( $row->job_params
), $row->job_id
);
191 // Remove any duplicates it may have later in the queue
192 $job->removeDuplicates();
194 wfProfileOut( __METHOD__
);
199 * Create the appropriate object to handle a specific job
201 * @param $command String: Job command
202 * @param $title Title: Associated title
203 * @param $params Array: Job parameters
204 * @param $id Int: Job identifier
207 static function factory( $command, $title, $params = false, $id = 0 ) {
208 global $wgJobClasses;
209 if( isset( $wgJobClasses[$command] ) ) {
210 $class = $wgJobClasses[$command];
211 return new $class( $title, $params, $id );
213 throw new MWException( "Invalid job command `{$command}`" );
216 static function makeBlob( $params ) {
217 if ( $params !== false ) {
218 return serialize( $params );
224 static function extractBlob( $blob ) {
225 if ( (string)$blob !== '' ) {
226 return unserialize( $blob );
233 * Batch-insert a group of jobs into the queue.
234 * This will be wrapped in a transaction with a forced commit.
236 * This may add duplicate at insert time, but they will be
237 * removed later on, when the first one is popped.
239 * @param $jobs array of Job objects
241 static function batchInsert( $jobs ) {
242 if ( !count( $jobs ) ) {
245 $dbw = wfGetDB( DB_MASTER
);
247 foreach ( $jobs as $job ) {
248 $rows[] = $job->insertFields();
249 if ( count( $rows ) >= 50 ) {
250 # Do a small transaction to avoid slave lag
252 $dbw->insert( 'job', $rows, __METHOD__
, 'IGNORE' );
257 if ( $rows ) { // last chunk
259 $dbw->insert( 'job', $rows, __METHOD__
, 'IGNORE' );
262 wfIncrStats( 'job-insert', count( $jobs ) );
266 * Insert a group of jobs into the queue.
268 * Same as batchInsert() but does not commit and can thus
269 * be rolled-back as part of a larger transaction. However,
270 * large batches of jobs can cause slave lag.
272 * @param $jobs array of Job objects
274 static function safeBatchInsert( $jobs ) {
275 if ( !count( $jobs ) ) {
278 $dbw = wfGetDB( DB_MASTER
);
280 foreach ( $jobs as $job ) {
281 $rows[] = $job->insertFields();
282 if ( count( $rows ) >= 500 ) {
283 $dbw->insert( 'job', $rows, __METHOD__
, 'IGNORE' );
287 if ( $rows ) { // last chunk
288 $dbw->insert( 'job', $rows, __METHOD__
, 'IGNORE' );
290 wfIncrStats( 'job-insert', count( $jobs ) );
293 /*-------------------------------------------------------------------------
294 * Non-static functions
295 *------------------------------------------------------------------------*/
300 * @param $params array
303 function __construct( $command, $title, $params = false, $id = 0 ) {
304 $this->command
= $command;
305 $this->title
= $title;
306 $this->params
= $params;
309 // A bit of premature generalisation
310 // Oh well, the whole class is premature generalisation really
311 $this->removeDuplicates
= true;
315 * Insert a single job into the queue.
316 * @return bool true on success
319 $fields = $this->insertFields();
321 $dbw = wfGetDB( DB_MASTER
);
323 if ( $this->removeDuplicates
) {
324 $res = $dbw->select( 'job', array( '1' ), $fields, __METHOD__
);
325 if ( $dbw->numRows( $res ) ) {
329 wfIncrStats( 'job-insert' );
330 return $dbw->insert( 'job', $fields, __METHOD__
);
333 protected function insertFields() {
334 $dbw = wfGetDB( DB_MASTER
);
336 'job_id' => $dbw->nextSequenceValue( 'job_job_id_seq' ),
337 'job_cmd' => $this->command
,
338 'job_namespace' => $this->title
->getNamespace(),
339 'job_title' => $this->title
->getDBkey(),
340 'job_params' => Job
::makeBlob( $this->params
)
345 * Remove jobs in the job queue which are duplicates of this job.
346 * This is deadlock-prone and so starts its own transaction.
348 function removeDuplicates() {
349 if ( !$this->removeDuplicates
) {
353 $fields = $this->insertFields();
354 unset( $fields['job_id'] );
355 $dbw = wfGetDB( DB_MASTER
);
357 $dbw->delete( 'job', $fields, __METHOD__
);
358 $affected = $dbw->affectedRows();
361 wfIncrStats( 'job-dup-delete', $affected );
365 function toString() {
367 if ( $this->params
) {
368 foreach ( $this->params
as $key => $value ) {
369 if ( $paramString != '' ) {
372 $paramString .= "$key=$value";
376 if ( is_object( $this->title
) ) {
377 $s = "{$this->command} " . $this->title
->getPrefixedDBkey();
378 if ( $paramString !== '' ) {
379 $s .= ' ' . $paramString;
383 return "{$this->command} $paramString";
387 protected function setLastError( $error ) {
388 $this->error
= $error;
391 function getLastError() {