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
22 use Wikimedia\Rdbms\IDatabase
;
23 use Wikimedia\Rdbms\DBConnRef
;
24 use Wikimedia\Rdbms\DBConnectionError
;
25 use Wikimedia\Rdbms\DBError
;
26 use MediaWiki\MediaWikiServices
;
27 use Wikimedia\ScopedCallback
;
30 * Class to handle job queues stored in the DB
35 class JobQueueDB
extends JobQueue
{
36 const CACHE_TTL_SHORT
= 30; // integer; seconds to cache info without re-validating
37 const MAX_AGE_PRUNE
= 604800; // integer; seconds a job can live once claimed
38 const MAX_JOB_RANDOM
= 2147483647; // integer; 2^31 - 1, used for job_random
39 const MAX_OFFSET
= 255; // integer; maximum number of rows to skip
41 /** @var WANObjectCache */
44 /** @var bool|string Name of an external DB cluster. False if not set */
45 protected $cluster = false;
48 * Additional parameters include:
49 * - cluster : The name of an external cluster registered via LBFactory.
50 * If not specified, the primary DB cluster for the wiki will be used.
51 * This can be overridden with a custom cluster so that DB handles will
52 * be retrieved via LBFactory::getExternalLB() and getConnection().
53 * @param array $params
55 protected function __construct( array $params ) {
56 parent
::__construct( $params );
58 $this->cluster
= $params['cluster'] ??
false;
59 $this->cache
= ObjectCache
::getMainWANInstance();
62 protected function supportedOrders() {
63 return [ 'random', 'timestamp', 'fifo' ];
66 protected function optimalOrder() {
71 * @see JobQueue::doIsEmpty()
74 protected function doIsEmpty() {
75 $dbr = $this->getReplicaDB();
77 $found = $dbr->selectField( // unclaimed job
78 'job', '1', [ 'job_cmd' => $this->type
, 'job_token' => '' ], __METHOD__
80 } catch ( DBError
$e ) {
81 $this->throwDBException( $e );
88 * @see JobQueue::doGetSize()
91 protected function doGetSize() {
92 $key = $this->getCacheKey( 'size' );
94 $size = $this->cache
->get( $key );
95 if ( is_int( $size ) ) {
100 $dbr = $this->getReplicaDB();
101 $size = (int)$dbr->selectField( 'job', 'COUNT(*)',
102 [ 'job_cmd' => $this->type
, 'job_token' => '' ],
105 } catch ( DBError
$e ) {
106 $this->throwDBException( $e );
108 $this->cache
->set( $key, $size, self
::CACHE_TTL_SHORT
);
114 * @see JobQueue::doGetAcquiredCount()
117 protected function doGetAcquiredCount() {
118 if ( $this->claimTTL
<= 0 ) {
119 return 0; // no acknowledgements
122 $key = $this->getCacheKey( 'acquiredcount' );
124 $count = $this->cache
->get( $key );
125 if ( is_int( $count ) ) {
129 $dbr = $this->getReplicaDB();
131 $count = (int)$dbr->selectField( 'job', 'COUNT(*)',
132 [ 'job_cmd' => $this->type
, "job_token != {$dbr->addQuotes( '' )}" ],
135 } catch ( DBError
$e ) {
136 $this->throwDBException( $e );
138 $this->cache
->set( $key, $count, self
::CACHE_TTL_SHORT
);
144 * @see JobQueue::doGetAbandonedCount()
146 * @throws MWException
148 protected function doGetAbandonedCount() {
149 if ( $this->claimTTL
<= 0 ) {
150 return 0; // no acknowledgements
153 $key = $this->getCacheKey( 'abandonedcount' );
155 $count = $this->cache
->get( $key );
156 if ( is_int( $count ) ) {
160 $dbr = $this->getReplicaDB();
162 $count = (int)$dbr->selectField( 'job', 'COUNT(*)',
164 'job_cmd' => $this->type
,
165 "job_token != {$dbr->addQuotes( '' )}",
166 "job_attempts >= " . $dbr->addQuotes( $this->maxTries
)
170 } catch ( DBError
$e ) {
171 $this->throwDBException( $e );
174 $this->cache
->set( $key, $count, self
::CACHE_TTL_SHORT
);
180 * @see JobQueue::doBatchPush()
181 * @param IJobSpecification[] $jobs
183 * @throws DBError|Exception
186 protected function doBatchPush( array $jobs, $flags ) {
187 $dbw = $this->getMasterDB();
188 // In general, there will be two cases here:
189 // a) sqlite; DB connection is probably a regular round-aware handle.
190 // If the connection is busy with a transaction, then defer the job writes
191 // until right before the main round commit step. Any errors that bubble
192 // up will rollback the main commit round.
193 // b) mysql/postgres; DB connection is generally a separate CONN_TRX_AUTOCOMMIT handle.
194 // No transaction is active nor will be started by writes, so enqueue the jobs
195 // now so that any errors will show up immediately as the interface expects. Any
196 // errors that bubble up will rollback the main commit round.
198 $dbw->onTransactionPreCommitOrIdle(
199 function ( IDatabase
$dbw ) use ( $jobs, $flags, $fname ) {
200 $this->doBatchPushInternal( $dbw, $jobs, $flags, $fname );
207 * This function should *not* be called outside of JobQueueDB
209 * @param IDatabase $dbw
210 * @param IJobSpecification[] $jobs
212 * @param string $method
216 public function doBatchPushInternal( IDatabase
$dbw, array $jobs, $flags, $method ) {
217 if ( !count( $jobs ) ) {
221 $rowSet = []; // (sha1 => job) map for jobs that are de-duplicated
222 $rowList = []; // list of jobs for jobs that are not de-duplicated
223 foreach ( $jobs as $job ) {
224 $row = $this->insertFields( $job, $dbw );
225 if ( $job->ignoreDuplicates() ) {
226 $rowSet[$row['job_sha1']] = $row;
232 if ( $flags & self
::QOS_ATOMIC
) {
233 $dbw->startAtomic( $method ); // wrap all the job additions in one transaction
236 // Strip out any duplicate jobs that are already in the queue...
237 if ( count( $rowSet ) ) {
238 $res = $dbw->select( 'job', 'job_sha1',
240 // No job_type condition since it's part of the job_sha1 hash
241 'job_sha1' => array_keys( $rowSet ),
242 'job_token' => '' // unclaimed
246 foreach ( $res as $row ) {
247 wfDebug( "Job with hash '{$row->job_sha1}' is a duplicate.\n" );
248 unset( $rowSet[$row->job_sha1
] ); // already enqueued
251 // Build the full list of job rows to insert
252 $rows = array_merge( $rowList, array_values( $rowSet ) );
253 // Insert the job rows in chunks to avoid replica DB lag...
254 foreach ( array_chunk( $rows, 50 ) as $rowBatch ) {
255 $dbw->insert( 'job', $rowBatch, $method );
257 JobQueue
::incrStats( 'inserts', $this->type
, count( $rows ) );
258 JobQueue
::incrStats( 'dupe_inserts', $this->type
,
259 count( $rowSet ) +
count( $rowList ) - count( $rows )
261 } catch ( DBError
$e ) {
262 $this->throwDBException( $e );
264 if ( $flags & self
::QOS_ATOMIC
) {
265 $dbw->endAtomic( $method );
270 * @see JobQueue::doPop()
273 protected function doPop() {
274 $dbw = $this->getMasterDB();
276 $autoTrx = $dbw->getFlag( DBO_TRX
); // get current setting
277 $dbw->clearFlag( DBO_TRX
); // make each query its own transaction
278 $scopedReset = new ScopedCallback( function () use ( $dbw, $autoTrx ) {
279 $dbw->setFlag( $autoTrx ? DBO_TRX
: 0 ); // restore old setting
282 $uuid = wfRandomString( 32 ); // pop attempt
283 $job = false; // job popped off
284 do { // retry when our row is invalid or deleted as a duplicate
285 // Try to reserve a row in the DB...
286 if ( in_array( $this->order
, [ 'fifo', 'timestamp' ] ) ) {
287 $row = $this->claimOldest( $uuid );
288 } else { // random first
289 $rand = mt_rand( 0, self
::MAX_JOB_RANDOM
); // encourage concurrent UPDATEs
290 $gte = (bool)mt_rand( 0, 1 ); // find rows with rand before/after $rand
291 $row = $this->claimRandom( $uuid, $rand, $gte );
293 // Check if we found a row to reserve...
295 break; // nothing to do
297 JobQueue
::incrStats( 'pops', $this->type
);
298 // Get the job object from the row...
299 $title = Title
::makeTitle( $row->job_namespace
, $row->job_title
);
300 $job = Job
::factory( $row->job_cmd
, $title,
301 self
::extractBlob( $row->job_params
), $row->job_id
);
302 $job->metadata
['id'] = $row->job_id
;
303 $job->metadata
['timestamp'] = $row->job_timestamp
;
307 if ( !$job ||
mt_rand( 0, 9 ) == 0 ) {
308 // Handled jobs that need to be recycled/deleted;
309 // any recycled jobs will be picked up next attempt
310 $this->recycleAndDeleteStaleJobs();
312 } catch ( DBError
$e ) {
313 $this->throwDBException( $e );
320 * Reserve a row with a single UPDATE without holding row locks over RTTs...
322 * @param string $uuid 32 char hex string
323 * @param int $rand Random unsigned integer (31 bits)
324 * @param bool $gte Search for job_random >= $random (otherwise job_random <= $random)
325 * @return stdClass|bool Row|false
327 protected function claimRandom( $uuid, $rand, $gte ) {
328 $dbw = $this->getMasterDB();
329 // Check cache to see if the queue has <= OFFSET items
330 $tinyQueue = $this->cache
->get( $this->getCacheKey( 'small' ) );
332 $row = false; // the row acquired
333 $invertedDirection = false; // whether one job_random direction was already scanned
334 // This uses a replication safe method for acquiring jobs. One could use UPDATE+LIMIT
335 // instead, but that either uses ORDER BY (in which case it deadlocks in MySQL) or is
336 // not replication safe. Due to https://bugs.mysql.com/bug.php?id=6980, subqueries cannot
337 // be used here with MySQL.
339 if ( $tinyQueue ) { // queue has <= MAX_OFFSET rows
340 // For small queues, using OFFSET will overshoot and return no rows more often.
341 // Instead, this uses job_random to pick a row (possibly checking both directions).
342 $ineq = $gte ?
'>=' : '<=';
343 $dir = $gte ?
'ASC' : 'DESC';
344 $row = $dbw->selectRow( 'job', self
::selectFields(), // find a random job
346 'job_cmd' => $this->type
,
347 'job_token' => '', // unclaimed
348 "job_random {$ineq} {$dbw->addQuotes( $rand )}" ],
350 [ 'ORDER BY' => "job_random {$dir}" ]
352 if ( !$row && !$invertedDirection ) {
354 $invertedDirection = true;
355 continue; // try the other direction
357 } else { // table *may* have >= MAX_OFFSET rows
358 // T44614: "ORDER BY job_random" with a job_random inequality causes high CPU
359 // in MySQL if there are many rows for some reason. This uses a small OFFSET
360 // instead of job_random for reducing excess claim retries.
361 $row = $dbw->selectRow( 'job', self
::selectFields(), // find a random job
363 'job_cmd' => $this->type
,
364 'job_token' => '', // unclaimed
367 [ 'OFFSET' => mt_rand( 0, self
::MAX_OFFSET
) ]
370 $tinyQueue = true; // we know the queue must have <= MAX_OFFSET rows
371 $this->cache
->set( $this->getCacheKey( 'small' ), 1, 30 );
372 continue; // use job_random
376 if ( $row ) { // claim the job
377 $dbw->update( 'job', // update by PK
379 'job_token' => $uuid,
380 'job_token_timestamp' => $dbw->timestamp(),
381 'job_attempts = job_attempts+1' ],
382 [ 'job_cmd' => $this->type
, 'job_id' => $row->job_id
, 'job_token' => '' ],
385 // This might get raced out by another runner when claiming the previously
386 // selected row. The use of job_random should minimize this problem, however.
387 if ( !$dbw->affectedRows() ) {
388 $row = false; // raced out
391 break; // nothing to do
399 * Reserve a row with a single UPDATE without holding row locks over RTTs...
401 * @param string $uuid 32 char hex string
402 * @return stdClass|bool Row|false
404 protected function claimOldest( $uuid ) {
405 $dbw = $this->getMasterDB();
407 $row = false; // the row acquired
409 if ( $dbw->getType() === 'mysql' ) {
410 // Per https://bugs.mysql.com/bug.php?id=6980, we can't use subqueries on the
411 // same table being changed in an UPDATE query in MySQL (gives Error: 1093).
412 // Oracle and Postgre have no such limitation. However, MySQL offers an
413 // alternative here by supporting ORDER BY + LIMIT for UPDATE queries.
414 $dbw->query( "UPDATE {$dbw->tableName( 'job' )} " .
416 "job_token = {$dbw->addQuotes( $uuid ) }, " .
417 "job_token_timestamp = {$dbw->addQuotes( $dbw->timestamp() )}, " .
418 "job_attempts = job_attempts+1 " .
420 "job_cmd = {$dbw->addQuotes( $this->type )} " .
421 "AND job_token = {$dbw->addQuotes( '' )} " .
422 ") ORDER BY job_id ASC LIMIT 1",
426 // Use a subquery to find the job, within an UPDATE to claim it.
427 // This uses as much of the DB wrapper functions as possible.
430 'job_token' => $uuid,
431 'job_token_timestamp' => $dbw->timestamp(),
432 'job_attempts = job_attempts+1' ],
434 $dbw->selectSQLText( 'job', 'job_id',
435 [ 'job_cmd' => $this->type
, 'job_token' => '' ],
437 [ 'ORDER BY' => 'job_id ASC', 'LIMIT' => 1 ] ) .
443 // Fetch any row that we just reserved...
444 if ( $dbw->affectedRows() ) {
445 $row = $dbw->selectRow( 'job', self
::selectFields(),
446 [ 'job_cmd' => $this->type
, 'job_token' => $uuid ], __METHOD__
448 if ( !$row ) { // raced out by duplicate job removal
449 wfDebug( "Row deleted as duplicate by another process.\n" );
452 break; // nothing to do
460 * @see JobQueue::doAck()
462 * @throws MWException
464 protected function doAck( Job
$job ) {
465 if ( !isset( $job->metadata
['id'] ) ) {
466 throw new MWException( "Job of type '{$job->getType()}' has no ID." );
469 $dbw = $this->getMasterDB();
471 $autoTrx = $dbw->getFlag( DBO_TRX
); // get current setting
472 $dbw->clearFlag( DBO_TRX
); // make each query its own transaction
473 $scopedReset = new ScopedCallback( function () use ( $dbw, $autoTrx ) {
474 $dbw->setFlag( $autoTrx ? DBO_TRX
: 0 ); // restore old setting
477 // Delete a row with a single DELETE without holding row locks over RTTs...
479 [ 'job_cmd' => $this->type
, 'job_id' => $job->metadata
['id'] ], __METHOD__
);
481 JobQueue
::incrStats( 'acks', $this->type
);
482 } catch ( DBError
$e ) {
483 $this->throwDBException( $e );
488 * @see JobQueue::doDeduplicateRootJob()
489 * @param IJobSpecification $job
490 * @throws MWException
493 protected function doDeduplicateRootJob( IJobSpecification
$job ) {
494 $params = $job->getParams();
495 if ( !isset( $params['rootJobSignature'] ) ) {
496 throw new MWException( "Cannot register root job; missing 'rootJobSignature'." );
497 } elseif ( !isset( $params['rootJobTimestamp'] ) ) {
498 throw new MWException( "Cannot register root job; missing 'rootJobTimestamp'." );
500 $key = $this->getRootJobCacheKey( $params['rootJobSignature'] );
501 // Callers should call JobQueueGroup::push() before this method so that if the insert
502 // fails, the de-duplication registration will be aborted. Since the insert is
503 // deferred till "transaction idle", do the same here, so that the ordering is
504 // maintained. Having only the de-duplication registration succeed would cause
505 // jobs to become no-ops without any actual jobs that made them redundant.
506 $dbw = $this->getMasterDB();
507 $cache = $this->dupCache
;
508 $dbw->onTransactionCommitOrIdle(
509 function () use ( $cache, $params, $key ) {
510 $timestamp = $cache->get( $key ); // current last timestamp of this job
511 if ( $timestamp && $timestamp >= $params['rootJobTimestamp'] ) {
512 return true; // a newer version of this root job was enqueued
515 // Update the timestamp of the last root job started at the location...
516 return $cache->set( $key, $params['rootJobTimestamp'], JobQueueDB
::ROOTJOB_TTL
);
525 * @see JobQueue::doDelete()
528 protected function doDelete() {
529 $dbw = $this->getMasterDB();
531 $dbw->delete( 'job', [ 'job_cmd' => $this->type
] );
532 } catch ( DBError
$e ) {
533 $this->throwDBException( $e );
540 * @see JobQueue::doWaitForBackups()
543 protected function doWaitForBackups() {
544 $lbFactory = MediaWikiServices
::getInstance()->getDBLoadBalancerFactory();
545 $lbFactory->waitForReplication(
546 [ 'domain' => $this->domain
, 'cluster' => $this->cluster
] );
552 protected function doFlushCaches() {
553 foreach ( [ 'size', 'acquiredcount' ] as $type ) {
554 $this->cache
->delete( $this->getCacheKey( $type ) );
559 * @see JobQueue::getAllQueuedJobs()
562 public function getAllQueuedJobs() {
563 return $this->getJobIterator( [ 'job_cmd' => $this->getType(), 'job_token' => '' ] );
567 * @see JobQueue::getAllAcquiredJobs()
570 public function getAllAcquiredJobs() {
571 return $this->getJobIterator( [ 'job_cmd' => $this->getType(), "job_token > ''" ] );
575 * @param array $conds Query conditions
578 protected function getJobIterator( array $conds ) {
579 $dbr = $this->getReplicaDB();
581 return new MappedIterator(
582 $dbr->select( 'job', self
::selectFields(), $conds ),
586 Title
::makeTitle( $row->job_namespace
, $row->job_title
),
587 strlen( $row->job_params
) ?
unserialize( $row->job_params
) : []
589 $job->metadata
['id'] = $row->job_id
;
590 $job->metadata
['timestamp'] = $row->job_timestamp
;
595 } catch ( DBError
$e ) {
596 $this->throwDBException( $e );
600 public function getCoalesceLocationInternal() {
601 return $this->cluster
602 ?
"DBCluster:{$this->cluster}:{$this->domain}"
603 : "LBFactory:{$this->domain}";
606 protected function doGetSiblingQueuesWithJobs( array $types ) {
607 $dbr = $this->getReplicaDB();
608 // @note: this does not check whether the jobs are claimed or not.
609 // This is useful so JobQueueGroup::pop() also sees queues that only
610 // have stale jobs. This lets recycleAndDeleteStaleJobs() re-enqueue
611 // failed jobs so that they can be popped again for that edge case.
612 $res = $dbr->select( 'job', 'DISTINCT job_cmd',
613 [ 'job_cmd' => $types ], __METHOD__
);
616 foreach ( $res as $row ) {
617 $types[] = $row->job_cmd
;
623 protected function doGetSiblingQueueSizes( array $types ) {
624 $dbr = $this->getReplicaDB();
625 $res = $dbr->select( 'job', [ 'job_cmd', 'COUNT(*) AS count' ],
626 [ 'job_cmd' => $types ], __METHOD__
, [ 'GROUP BY' => 'job_cmd' ] );
629 foreach ( $res as $row ) {
630 $sizes[$row->job_cmd
] = (int)$row->count
;
637 * Recycle or destroy any jobs that have been claimed for too long
639 * @return int Number of jobs recycled/deleted
641 public function recycleAndDeleteStaleJobs() {
643 $count = 0; // affected rows
644 $dbw = $this->getMasterDB();
647 if ( !$dbw->lock( "jobqueue-recycle-{$this->type}", __METHOD__
, 1 ) ) {
648 return $count; // already in progress
651 // Remove claims on jobs acquired for too long if enabled...
652 if ( $this->claimTTL
> 0 ) {
653 $claimCutoff = $dbw->timestamp( $now - $this->claimTTL
);
654 // Get the IDs of jobs that have be claimed but not finished after too long.
655 // These jobs can be recycled into the queue by expiring the claim. Selecting
656 // the IDs first means that the UPDATE can be done by primary key (less deadlocks).
657 $res = $dbw->select( 'job', 'job_id',
659 'job_cmd' => $this->type
,
660 "job_token != {$dbw->addQuotes( '' )}", // was acquired
661 "job_token_timestamp < {$dbw->addQuotes( $claimCutoff )}", // stale
662 "job_attempts < {$dbw->addQuotes( $this->maxTries )}" ], // retries left
668 }, iterator_to_array( $res )
670 if ( count( $ids ) ) {
671 // Reset job_token for these jobs so that other runners will pick them up.
672 // Set the timestamp to the current time, as it is useful to now that the job
673 // was already tried before (the timestamp becomes the "released" time).
677 'job_token_timestamp' => $dbw->timestamp( $now ) ], // time of release
682 $affected = $dbw->affectedRows();
684 JobQueue
::incrStats( 'recycles', $this->type
, $affected );
685 $this->aggr
->notifyQueueNonEmpty( $this->domain
, $this->type
);
689 // Just destroy any stale jobs...
690 $pruneCutoff = $dbw->timestamp( $now - self
::MAX_AGE_PRUNE
);
692 'job_cmd' => $this->type
,
693 "job_token != {$dbw->addQuotes( '' )}", // was acquired
694 "job_token_timestamp < {$dbw->addQuotes( $pruneCutoff )}" // stale
696 if ( $this->claimTTL
> 0 ) { // only prune jobs attempted too many times...
697 $conds[] = "job_attempts >= {$dbw->addQuotes( $this->maxTries )}";
699 // Get the IDs of jobs that are considered stale and should be removed. Selecting
700 // the IDs first means that the UPDATE can be done by primary key (less deadlocks).
701 $res = $dbw->select( 'job', 'job_id', $conds, __METHOD__
);
705 }, iterator_to_array( $res )
707 if ( count( $ids ) ) {
708 $dbw->delete( 'job', [ 'job_id' => $ids ], __METHOD__
);
709 $affected = $dbw->affectedRows();
711 JobQueue
::incrStats( 'abandons', $this->type
, $affected );
714 $dbw->unlock( "jobqueue-recycle-{$this->type}", __METHOD__
);
715 } catch ( DBError
$e ) {
716 $this->throwDBException( $e );
723 * @param IJobSpecification $job
724 * @param IDatabase $db
727 protected function insertFields( IJobSpecification
$job, IDatabase
$db ) {
729 // Fields that describe the nature of the job
730 'job_cmd' => $job->getType(),
731 'job_namespace' => $job->getTitle()->getNamespace(),
732 'job_title' => $job->getTitle()->getDBkey(),
733 'job_params' => self
::makeBlob( $job->getParams() ),
734 // Additional job metadata
735 'job_timestamp' => $db->timestamp(),
736 'job_sha1' => Wikimedia\base_convert
(
737 sha1( serialize( $job->getDeduplicationInfo() ) ),
740 'job_random' => mt_rand( 0, self
::MAX_JOB_RANDOM
)
745 * @throws JobQueueConnectionError
748 protected function getReplicaDB() {
750 return $this->getDB( DB_REPLICA
);
751 } catch ( DBConnectionError
$e ) {
752 throw new JobQueueConnectionError( "DBConnectionError:" . $e->getMessage() );
757 * @throws JobQueueConnectionError
760 protected function getMasterDB() {
762 return $this->getDB( DB_MASTER
);
763 } catch ( DBConnectionError
$e ) {
764 throw new JobQueueConnectionError( "DBConnectionError:" . $e->getMessage() );
769 * @param int $index (DB_REPLICA/DB_MASTER)
772 protected function getDB( $index ) {
773 $lbFactory = MediaWikiServices
::getInstance()->getDBLoadBalancerFactory();
774 $lb = ( $this->cluster
!== false )
775 ?
$lbFactory->getExternalLB( $this->cluster
)
776 : $lbFactory->getMainLB( $this->domain
);
778 return ( $lb->getServerType( $lb->getWriterIndex() ) !== 'sqlite' )
779 // Keep a separate connection to avoid contention and deadlocks;
780 // However, SQLite has the opposite behavior due to DB-level locking.
781 ?
$lb->getConnectionRef( $index, [], $this->domain
, $lb::CONN_TRX_AUTOCOMMIT
)
782 // Jobs insertion will be defered until the PRESEND stage to reduce contention.
783 : $lb->getConnectionRef( $index, [], $this->domain
);
787 * @param string $property
790 private function getCacheKey( $property ) {
791 $cluster = is_string( $this->cluster
) ?
$this->cluster
: 'main';
793 return $this->cache
->makeGlobalKey(
803 * @param array|bool $params
806 protected static function makeBlob( $params ) {
807 if ( $params !== false ) {
808 return serialize( $params );
815 * @param string $blob
818 protected static function extractBlob( $blob ) {
819 if ( (string)$blob !== '' ) {
820 return unserialize( $blob );
828 * @throws JobQueueError
830 protected function throwDBException( DBError
$e ) {
831 throw new JobQueueError( get_class( $e ) . ": " . $e->getMessage() );
835 * Return the list of job fields that should be selected.
839 public static function selectFields() {
850 'job_token_timestamp',