/**
* Pop a job off of the queue.
* This requires $wgJobClasses to be set for the given job type.
* Outside callers should use JobQueueGroup::pop() instead of this function.
*
* @throws MWException
* @return Job|bool Returns false if there are no jobs
*/
public final function pop()
{
global $wgJobClasses;
$this->assertNotReadOnly();
if ($this->wiki !== wfWikiID()) {
throw new MWException("Cannot pop '{$this->type}' job off foreign wiki queue.");
} elseif (!isset($wgJobClasses[$this->type])) {
// Do not pop jobs if there is no class for the queue type
throw new MWException("Unrecognized job type '{$this->type}'.");
}
$job = $this->doPop();
if (!$job) {
$this->aggr->notifyQueueEmpty($this->wiki, $this->type);
}
// Flag this job as an old duplicate based on its "root" job...
try {
if ($job && $this->isRootJobOldDuplicate($job)) {
JobQueue::incrStats('dupe_pops', $this->type);
$job = DuplicateJob::newFromJob($job);
// convert to a no-op
}
} catch (Exception $e) {
// don't lose jobs over this
}
return $job;
}
/**
* Pop a job off of the queue.
* This requires $wgJobClasses to be set for the given job type.
* Outside callers should use JobQueueGroup::pop() instead of this function.
*
* @throws MWException
* @return Job|bool Returns false if there are no jobs
*/
public final function pop()
{
global $wgJobClasses;
if ($this->wiki !== wfWikiID()) {
throw new MWException("Cannot pop '{$this->type}' job off foreign wiki queue.");
} elseif (!isset($wgJobClasses[$this->type])) {
// Do not pop jobs if there is no class for the queue type
throw new MWException("Unrecognized job type '{$this->type}'.");
}
wfProfileIn(__METHOD__);
$job = $this->doPop();
wfProfileOut(__METHOD__);
// Flag this job as an old duplicate based on its "root" job...
try {
if ($job && $this->isRootJobOldDuplicate($job)) {
JobQueue::incrStats('job-pop-duplicate', $this->type, 1, $this->wiki);
$job = DuplicateJob::newFromJob($job);
// convert to a no-op
}
} catch (MWException $e) {
// don't lose jobs over this
}
return $job;
}
/**
* @see JobQueue::doPop()
* @return Job|bool
*/
protected function doPop()
{
global $wgMemc;
if ($wgMemc->get($this->getCacheKey('empty')) === 'true') {
return false;
// queue is empty
}
list($dbw, $scope) = $this->getMasterDB();
$dbw->commit(__METHOD__, 'flush');
// flush existing transaction
$autoTrx = $dbw->getFlag(DBO_TRX);
// get current setting
$dbw->clearFlag(DBO_TRX);
// make each query its own transaction
$scopedReset = new ScopedCallback(function () use($dbw, $autoTrx) {
$dbw->setFlag($autoTrx ? DBO_TRX : 0);
// restore old setting
});
$uuid = wfRandomString(32);
// pop attempt
$job = false;
// job popped off
do {
// retry when our row is invalid or deleted as a duplicate
// Try to reserve a row in the DB...
if (in_array($this->order, array('fifo', 'timestamp'))) {
$row = $this->claimOldest($uuid);
} else {
// random first
$rand = mt_rand(0, self::MAX_JOB_RANDOM);
// encourage concurrent UPDATEs
$gte = (bool) mt_rand(0, 1);
// find rows with rand before/after $rand
$row = $this->claimRandom($uuid, $rand, $gte);
}
// Check if we found a row to reserve...
if (!$row) {
$wgMemc->set($this->getCacheKey('empty'), 'true', self::CACHE_TTL_LONG);
break;
// nothing to do
}
wfIncrStats('job-pop');
// Get the job object from the row...
$title = Title::makeTitleSafe($row->job_namespace, $row->job_title);
if (!$title) {
$dbw->delete('job', array('job_id' => $row->job_id), __METHOD__);
wfDebugLog('JobQueueDB', "Row has invalid title '{$row->job_title}'.");
continue;
// try again
}
$job = Job::factory($row->job_cmd, $title, self::extractBlob($row->job_params), $row->job_id);
$job->id = $row->job_id;
// XXX: work around broken subclasses
// Flag this job as an old duplicate based on its "root" job...
if ($this->isRootJobOldDuplicate($job)) {
wfIncrStats('job-pop-duplicate');
$job = DuplicateJob::newFromJob($job);
// convert to a no-op
}
break;
// done
} while (true);
return $job;
}
