3 * Database-backed job queue code.
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License as published by
7 * the Free Software Foundation; either version 2 of the License, or
8 * (at your option) any later version.
10 * This program is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 * GNU General Public License for more details.
15 * You should have received a copy of the GNU General Public License along
16 * with this program; if not, write to the Free Software Foundation, Inc.,
17 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
18 * http://www.gnu.org/copyleft/gpl.html
21 * @author Aaron Schulz
25 * Class to handle job queues stored in the DB
30 class JobQueueDB
extends JobQueue
{
31 const ROOTJOB_TTL
= 1209600; // integer; seconds to remember root jobs (14 days)
32 const CACHE_TTL_SHORT
= 30; // integer; seconds to cache info without re-validating
33 const CACHE_TTL_LONG
= 300; // integer; seconds to cache info that is kept up to date
34 const MAX_AGE_PRUNE
= 604800; // integer; seconds a job can live once claimed
35 const MAX_JOB_RANDOM
= 2147483647; // integer; 2^31 - 1, used for job_random
36 const MAX_OFFSET
= 255; // integer; maximum number of rows to skip
41 protected $cluster = false; // string; name of an external DB cluster
44 * Additional parameters include:
45 * - cluster : The name of an external cluster registered via LBFactory.
46 * If not specified, the primary DB cluster for the wiki will be used.
47 * This can be overridden with a custom cluster so that DB handles will
48 * be retrieved via LBFactory::getExternalLB() and getConnection().
49 * @param $params array
51 protected function __construct( array $params ) {
52 parent
::__construct( $params );
53 $this->cluster
= isset( $params['cluster'] ) ?
$params['cluster'] : false;
54 $this->cache
= wfGetMainCache();
57 protected function supportedOrders() {
58 return array( 'random', 'timestamp', 'fifo' );
61 protected function optimalOrder() {
66 * @see JobQueue::doIsEmpty()
69 protected function doIsEmpty() {
70 $key = $this->getCacheKey( 'empty' );
72 $isEmpty = $this->cache
->get( $key );
73 if ( $isEmpty === 'true' ) {
75 } elseif ( $isEmpty === 'false' ) {
79 list( $dbr, $scope ) = $this->getSlaveDB();
80 $found = $dbr->selectField( // unclaimed job
81 'job', '1', array( 'job_cmd' => $this->type
, 'job_token' => '' ), __METHOD__
83 $this->cache
->add( $key, $found ?
'false' : 'true', self
::CACHE_TTL_LONG
);
89 * @see JobQueue::doGetSize()
92 protected function doGetSize() {
93 $key = $this->getCacheKey( 'size' );
95 $size = $this->cache
->get( $key );
96 if ( is_int( $size ) ) {
100 list( $dbr, $scope ) = $this->getSlaveDB();
101 $size = (int)$dbr->selectField( 'job', 'COUNT(*)',
102 array( 'job_cmd' => $this->type
, 'job_token' => '' ),
105 $this->cache
->set( $key, $size, self
::CACHE_TTL_SHORT
);
111 * @see JobQueue::doGetAcquiredCount()
114 protected function doGetAcquiredCount() {
115 if ( $this->claimTTL
<= 0 ) {
116 return 0; // no acknowledgements
119 $key = $this->getCacheKey( 'acquiredcount' );
121 $count = $this->cache
->get( $key );
122 if ( is_int( $count ) ) {
126 list( $dbr, $scope ) = $this->getSlaveDB();
127 $count = (int)$dbr->selectField( 'job', 'COUNT(*)',
128 array( 'job_cmd' => $this->type
, "job_token != {$dbr->addQuotes( '' )}" ),
131 $this->cache
->set( $key, $count, self
::CACHE_TTL_SHORT
);
137 * @see JobQueue::doBatchPush()
140 * @throws DBError|Exception
143 protected function doBatchPush( array $jobs, $flags ) {
144 if ( count( $jobs ) ) {
145 list( $dbw, $scope ) = $this->getMasterDB();
147 $rowSet = array(); // (sha1 => job) map for jobs that are de-duplicated
148 $rowList = array(); // list of jobs for jobs that are are not de-duplicated
150 foreach ( $jobs as $job ) {
151 $row = $this->insertFields( $job );
152 if ( $job->ignoreDuplicates() ) {
153 $rowSet[$row['job_sha1']] = $row;
159 $key = $this->getCacheKey( 'empty' );
160 $atomic = ( $flags & self
::QoS_Atomic
);
161 $cache = $this->cache
;
163 $dbw->onTransactionIdle(
164 function() use ( $dbw, $cache, $rowSet, $rowList, $atomic, $key, $scope
167 $dbw->begin( __METHOD__
); // wrap all the job additions in one transaction
170 // Strip out any duplicate jobs that are already in the queue...
171 if ( count( $rowSet ) ) {
172 $res = $dbw->select( 'job', 'job_sha1',
174 // No job_type condition since it's part of the job_sha1 hash
175 'job_sha1' => array_keys( $rowSet ),
176 'job_token' => '' // unclaimed
180 foreach ( $res as $row ) {
181 wfDebug( "Job with hash '{$row->job_sha1}' is a duplicate." );
182 unset( $rowSet[$row->job_sha1
] ); // already enqueued
185 // Build the full list of job rows to insert
186 $rows = array_merge( $rowList, array_values( $rowSet ) );
187 // Insert the job rows in chunks to avoid slave lag...
188 foreach ( array_chunk( $rows, 50 ) as $rowBatch ) {
189 $dbw->insert( 'job', $rowBatch, __METHOD__
);
191 wfIncrStats( 'job-insert', count( $rows ) );
192 wfIncrStats( 'job-insert-duplicate',
193 count( $rowSet ) +
count( $rowList ) - count( $rows ) );
194 } catch ( DBError
$e ) {
196 $dbw->rollback( __METHOD__
);
201 $dbw->commit( __METHOD__
);
204 $cache->set( $key, 'false', JobQueueDB
::CACHE_TTL_LONG
);
212 * @see JobQueue::doPop()
215 protected function doPop() {
216 if ( $this->cache
->get( $this->getCacheKey( 'empty' ) ) === 'true' ) {
217 return false; // queue is empty
220 list( $dbw, $scope ) = $this->getMasterDB();
221 $dbw->commit( __METHOD__
, 'flush' ); // flush existing transaction
223 $uuid = wfRandomString( 32 ); // pop attempt
224 $job = false; // job popped off
225 do { // retry when our row is invalid or deleted as a duplicate
226 // Try to reserve a row in the DB...
227 if ( in_array( $this->order
, array( 'fifo', 'timestamp' ) ) ) {
228 $row = $this->claimOldest( $uuid );
229 } else { // random first
230 $rand = mt_rand( 0, self
::MAX_JOB_RANDOM
); // encourage concurrent UPDATEs
231 $gte = (bool)mt_rand( 0, 1 ); // find rows with rand before/after $rand
232 $row = $this->claimRandom( $uuid, $rand, $gte );
234 // Check if we found a row to reserve...
236 $this->cache
->set( $this->getCacheKey( 'empty' ), 'true', self
::CACHE_TTL_LONG
);
237 break; // nothing to do
239 wfIncrStats( 'job-pop' );
240 // Get the job object from the row...
241 $title = Title
::makeTitleSafe( $row->job_namespace
, $row->job_title
);
243 $dbw->delete( 'job', array( 'job_id' => $row->job_id
), __METHOD__
);
244 wfDebugLog( 'JobQueueDB', "Row has invalid title '{$row->job_title}'." );
245 continue; // try again
247 $job = Job
::factory( $row->job_cmd
, $title,
248 self
::extractBlob( $row->job_params
), $row->job_id
);
249 $job->id
= $row->job_id
; // XXX: work around broken subclasses
250 // Flag this job as an old duplicate based on its "root" job...
251 if ( $this->isRootJobOldDuplicate( $job ) ) {
252 wfIncrStats( 'job-pop-duplicate' );
253 $job = DuplicateJob
::newFromJob( $job ); // convert to a no-op
262 * Reserve a row with a single UPDATE without holding row locks over RTTs...
264 * @param string $uuid 32 char hex string
265 * @param $rand integer Random unsigned integer (31 bits)
266 * @param bool $gte Search for job_random >= $random (otherwise job_random <= $random)
269 protected function claimRandom( $uuid, $rand, $gte ) {
270 list( $dbw, $scope ) = $this->getMasterDB();
271 // Check cache to see if the queue has <= OFFSET items
272 $tinyQueue = $this->cache
->get( $this->getCacheKey( 'small' ) );
274 $row = false; // the row acquired
275 $invertedDirection = false; // whether one job_random direction was already scanned
276 // This uses a replication safe method for acquiring jobs. One could use UPDATE+LIMIT
277 // instead, but that either uses ORDER BY (in which case it deadlocks in MySQL) or is
278 // not replication safe. Due to http://bugs.mysql.com/bug.php?id=6980, subqueries cannot
279 // be used here with MySQL.
281 if ( $tinyQueue ) { // queue has <= MAX_OFFSET rows
282 // For small queues, using OFFSET will overshoot and return no rows more often.
283 // Instead, this uses job_random to pick a row (possibly checking both directions).
284 $ineq = $gte ?
'>=' : '<=';
285 $dir = $gte ?
'ASC' : 'DESC';
286 $row = $dbw->selectRow( 'job', '*', // find a random job
288 'job_cmd' => $this->type
,
289 'job_token' => '', // unclaimed
290 "job_random {$ineq} {$dbw->addQuotes( $rand )}" ),
292 array( 'ORDER BY' => "job_random {$dir}" )
294 if ( !$row && !$invertedDirection ) {
296 $invertedDirection = true;
297 continue; // try the other direction
299 } else { // table *may* have >= MAX_OFFSET rows
300 // Bug 42614: "ORDER BY job_random" with a job_random inequality causes high CPU
301 // in MySQL if there are many rows for some reason. This uses a small OFFSET
302 // instead of job_random for reducing excess claim retries.
303 $row = $dbw->selectRow( 'job', '*', // find a random job
305 'job_cmd' => $this->type
,
306 'job_token' => '', // unclaimed
309 array( 'OFFSET' => mt_rand( 0, self
::MAX_OFFSET
) )
312 $tinyQueue = true; // we know the queue must have <= MAX_OFFSET rows
313 $this->cache
->set( $this->getCacheKey( 'small' ), 1, 30 );
314 continue; // use job_random
317 if ( $row ) { // claim the job
318 $dbw->update( 'job', // update by PK
320 'job_token' => $uuid,
321 'job_token_timestamp' => $dbw->timestamp(),
322 'job_attempts = job_attempts+1' ),
323 array( 'job_cmd' => $this->type
, 'job_id' => $row->job_id
, 'job_token' => '' ),
326 // This might get raced out by another runner when claiming the previously
327 // selected row. The use of job_random should minimize this problem, however.
328 if ( !$dbw->affectedRows() ) {
329 $row = false; // raced out
332 break; // nothing to do
340 * Reserve a row with a single UPDATE without holding row locks over RTTs...
342 * @param string $uuid 32 char hex string
345 protected function claimOldest( $uuid ) {
346 list( $dbw, $scope ) = $this->getMasterDB();
348 $row = false; // the row acquired
350 if ( $dbw->getType() === 'mysql' ) {
351 // Per http://bugs.mysql.com/bug.php?id=6980, we can't use subqueries on the
352 // same table being changed in an UPDATE query in MySQL (gives Error: 1093).
353 // Oracle and Postgre have no such limitation. However, MySQL offers an
354 // alternative here by supporting ORDER BY + LIMIT for UPDATE queries.
355 $dbw->query( "UPDATE {$dbw->tableName( 'job' )} " .
357 "job_token = {$dbw->addQuotes( $uuid ) }, " .
358 "job_token_timestamp = {$dbw->addQuotes( $dbw->timestamp() )}, " .
359 "job_attempts = job_attempts+1 " .
361 "job_cmd = {$dbw->addQuotes( $this->type )} " .
362 "AND job_token = {$dbw->addQuotes( '' )} " .
363 ") ORDER BY job_id ASC LIMIT 1",
367 // Use a subquery to find the job, within an UPDATE to claim it.
368 // This uses as much of the DB wrapper functions as possible.
371 'job_token' => $uuid,
372 'job_token_timestamp' => $dbw->timestamp(),
373 'job_attempts = job_attempts+1' ),
374 array( 'job_id = (' .
375 $dbw->selectSQLText( 'job', 'job_id',
376 array( 'job_cmd' => $this->type
, 'job_token' => '' ),
378 array( 'ORDER BY' => 'job_id ASC', 'LIMIT' => 1 ) ) .
384 // Fetch any row that we just reserved...
385 if ( $dbw->affectedRows() ) {
386 $row = $dbw->selectRow( 'job', '*',
387 array( 'job_cmd' => $this->type
, 'job_token' => $uuid ), __METHOD__
389 if ( !$row ) { // raced out by duplicate job removal
390 wfDebugLog( 'JobQueueDB', "Row deleted as duplicate by another process." );
393 break; // nothing to do
401 * Recycle or destroy any jobs that have been claimed for too long
403 * @return integer Number of jobs recycled/deleted
405 public function recycleAndDeleteStaleJobs() {
407 list( $dbw, $scope ) = $this->getMasterDB();
408 $count = 0; // affected rows
410 if ( !$dbw->lock( "jobqueue-recycle-{$this->type}", __METHOD__
, 1 ) ) {
411 return $count; // already in progress
414 // Remove claims on jobs acquired for too long if enabled...
415 if ( $this->claimTTL
> 0 ) {
416 $claimCutoff = $dbw->timestamp( $now - $this->claimTTL
);
417 // Get the IDs of jobs that have be claimed but not finished after too long.
418 // These jobs can be recycled into the queue by expiring the claim. Selecting
419 // the IDs first means that the UPDATE can be done by primary key (less deadlocks).
420 $res = $dbw->select( 'job', 'job_id',
422 'job_cmd' => $this->type
,
423 "job_token != {$dbw->addQuotes( '' )}", // was acquired
424 "job_token_timestamp < {$dbw->addQuotes( $claimCutoff )}", // stale
425 "job_attempts < {$dbw->addQuotes( $this->maxTries )}" ), // retries left
428 $ids = array_map( function( $o ) { return $o->job_id
; }, iterator_to_array( $res ) );
429 if ( count( $ids ) ) {
430 // Reset job_token for these jobs so that other runners will pick them up.
431 // Set the timestamp to the current time, as it is useful to now that the job
432 // was already tried before (the timestamp becomes the "released" time).
436 'job_token_timestamp' => $dbw->timestamp( $now ) ), // time of release
441 $count +
= $dbw->affectedRows();
442 wfIncrStats( 'job-recycle', $dbw->affectedRows() );
443 $this->cache
->set( $this->getCacheKey( 'empty' ), 'false', self
::CACHE_TTL_LONG
);
447 // Just destroy any stale jobs...
448 $pruneCutoff = $dbw->timestamp( $now - self
::MAX_AGE_PRUNE
);
450 'job_cmd' => $this->type
,
451 "job_token != {$dbw->addQuotes( '' )}", // was acquired
452 "job_token_timestamp < {$dbw->addQuotes( $pruneCutoff )}" // stale
454 if ( $this->claimTTL
> 0 ) { // only prune jobs attempted too many times...
455 $conds[] = "job_attempts >= {$dbw->addQuotes( $this->maxTries )}";
457 // Get the IDs of jobs that are considered stale and should be removed. Selecting
458 // the IDs first means that the UPDATE can be done by primary key (less deadlocks).
459 $res = $dbw->select( 'job', 'job_id', $conds, __METHOD__
);
460 $ids = array_map( function( $o ) { return $o->job_id
; }, iterator_to_array( $res ) );
461 if ( count( $ids ) ) {
462 $dbw->delete( 'job', array( 'job_id' => $ids ), __METHOD__
);
463 $count +
= $dbw->affectedRows();
466 $dbw->unlock( "jobqueue-recycle-{$this->type}", __METHOD__
);
472 * @see JobQueue::doAck()
474 * @throws MWException
477 protected function doAck( Job
$job ) {
478 if ( !$job->getId() ) {
479 throw new MWException( "Job of type '{$job->getType()}' has no ID." );
482 list( $dbw, $scope ) = $this->getMasterDB();
483 $dbw->commit( __METHOD__
, 'flush' ); // flush existing transaction
485 // Delete a row with a single DELETE without holding row locks over RTTs...
487 array( 'job_cmd' => $this->type
, 'job_id' => $job->getId() ), __METHOD__
);
493 * @see JobQueue::doDeduplicateRootJob()
495 * @throws MWException
498 protected function doDeduplicateRootJob( Job
$job ) {
499 $params = $job->getParams();
500 if ( !isset( $params['rootJobSignature'] ) ) {
501 throw new MWException( "Cannot register root job; missing 'rootJobSignature'." );
502 } elseif ( !isset( $params['rootJobTimestamp'] ) ) {
503 throw new MWException( "Cannot register root job; missing 'rootJobTimestamp'." );
505 $key = $this->getRootJobCacheKey( $params['rootJobSignature'] );
506 // Callers should call batchInsert() and then this function so that if the insert
507 // fails, the de-duplication registration will be aborted. Since the insert is
508 // deferred till "transaction idle", do the same here, so that the ordering is
509 // maintained. Having only the de-duplication registration succeed would cause
510 // jobs to become no-ops without any actual jobs that made them redundant.
511 list( $dbw, $scope ) = $this->getMasterDB();
512 $cache = $this->cache
;
513 $dbw->onTransactionIdle( function() use ( $cache, $params, $key, $scope ) {
514 $timestamp = $cache->get( $key ); // current last timestamp of this job
515 if ( $timestamp && $timestamp >= $params['rootJobTimestamp'] ) {
516 return true; // a newer version of this root job was enqueued
519 // Update the timestamp of the last root job started at the location...
520 return $cache->set( $key, $params['rootJobTimestamp'], JobQueueDB
::ROOTJOB_TTL
);
527 * Check if the "root" job of a given job has been superseded by a newer one
532 protected function isRootJobOldDuplicate( Job
$job ) {
533 $params = $job->getParams();
534 if ( !isset( $params['rootJobSignature'] ) ) {
535 return false; // job has no de-deplication info
536 } elseif ( !isset( $params['rootJobTimestamp'] ) ) {
537 trigger_error( "Cannot check root job; missing 'rootJobTimestamp'." );
541 // Get the last time this root job was enqueued
542 $timestamp = $this->cache
->get( $this->getRootJobCacheKey( $params['rootJobSignature'] ) );
544 // Check if a new root job was started at the location after this one's...
545 return ( $timestamp && $timestamp > $params['rootJobTimestamp'] );
549 * @see JobQueue::doWaitForBackups()
552 protected function doWaitForBackups() {
559 protected function doGetPeriodicTasks() {
561 'recycleAndDeleteStaleJobs' => array(
562 'callback' => array( $this, 'recycleAndDeleteStaleJobs' ),
563 'period' => ceil( $this->claimTTL
/ 2 )
571 protected function doFlushCaches() {
572 foreach ( array( 'empty', 'size', 'acquiredcount' ) as $type ) {
573 $this->cache
->delete( $this->getCacheKey( $type ) );
578 * @see JobQueue::getAllQueuedJobs()
581 public function getAllQueuedJobs() {
582 list( $dbr, $scope ) = $this->getSlaveDB();
583 return new MappedIterator(
584 $dbr->select( 'job', '*', array( 'job_cmd' => $this->getType(), 'job_token' => '' ) ),
585 function( $row ) use ( $scope ) {
588 Title
::makeTitle( $row->job_namespace
, $row->job_title
),
589 strlen( $row->job_params
) ?
unserialize( $row->job_params
) : false,
592 $job->id
= $row->job_id
; // XXX: work around broken subclasses
599 * @return Array (DatabaseBase, ScopedCallback)
601 protected function getSlaveDB() {
602 return $this->getDB( DB_SLAVE
);
606 * @return Array (DatabaseBase, ScopedCallback)
608 protected function getMasterDB() {
609 return $this->getDB( DB_MASTER
);
613 * @param $index integer (DB_SLAVE/DB_MASTER)
614 * @return Array (DatabaseBase, ScopedCallback)
616 protected function getDB( $index ) {
617 $lb = ( $this->cluster
!== false )
618 ?
wfGetLBFactory()->getExternalLB( $this->cluster
, $this->wiki
)
619 : wfGetLB( $this->wiki
);
620 $conn = $lb->getConnection( $index, array(), $this->wiki
);
623 new ScopedCallback( function() use ( $lb, $conn ) {
624 $lb->reuseConnection( $conn );
633 protected function insertFields( Job
$job ) {
634 list( $dbw, $scope ) = $this->getMasterDB();
636 // Fields that describe the nature of the job
637 'job_cmd' => $job->getType(),
638 'job_namespace' => $job->getTitle()->getNamespace(),
639 'job_title' => $job->getTitle()->getDBkey(),
640 'job_params' => self
::makeBlob( $job->getParams() ),
641 // Additional job metadata
642 'job_id' => $dbw->nextSequenceValue( 'job_job_id_seq' ),
643 'job_timestamp' => $dbw->timestamp(),
644 'job_sha1' => wfBaseConvert(
645 sha1( serialize( $job->getDeduplicationInfo() ) ),
648 'job_random' => mt_rand( 0, self
::MAX_JOB_RANDOM
)
655 private function getCacheKey( $property ) {
656 list( $db, $prefix ) = wfSplitWikiID( $this->wiki
);
657 return wfForeignMemcKey( $db, $prefix, 'jobqueue', $this->type
, $property );
661 * @param string $signature Hash identifier of the root job
664 private function getRootJobCacheKey( $signature ) {
665 list( $db, $prefix ) = wfSplitWikiID( $this->wiki
);
666 return wfForeignMemcKey( $db, $prefix, 'jobqueue', $this->type
, 'rootjob', $signature );
673 protected static function makeBlob( $params ) {
674 if ( $params !== false ) {
675 return serialize( $params );
685 protected static function extractBlob( $blob ) {
686 if ( (string)$blob !== '' ) {
687 return unserialize( $blob );