Your IP : 108.162.216.193
<?php
/**
* Database-backed job queue code.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
* http://www.gnu.org/copyleft/gpl.html
*
* @file
* @author Aaron Schulz
*/
/**
* Class to handle job queues stored in the DB
*
* @ingroup JobQueue
* @since 1.21
*/
class JobQueueDB extends JobQueue {
const ROOTJOB_TTL = 1209600; // integer; seconds to remember root jobs (14 days)
const CACHE_TTL_SHORT = 30; // integer; seconds to cache info without re-validating
const CACHE_TTL_LONG = 300; // integer; seconds to cache info that is kept up to date
const MAX_AGE_PRUNE = 604800; // integer; seconds a job can live once claimed
const MAX_JOB_RANDOM = 2147483647; // integer; 2^31 - 1, used for job_random
const MAX_OFFSET = 255; // integer; maximum number of rows to skip
protected $cluster = false; // string; name of an external DB cluster
/**
* Additional parameters include:
* - cluster : The name of an external cluster registered via LBFactory.
* If not specified, the primary DB cluster for the wiki will be used.
* This can be overridden with a custom cluster so that DB handles will
* be retrieved via LBFactory::getExternalLB() and getConnection().
* @param $params array
*/
protected function __construct( array $params ) {
parent::__construct( $params );
$this->cluster = isset( $params['cluster'] ) ? $params['cluster'] : false;
}
protected function supportedOrders() {
return array( 'random', 'timestamp', 'fifo' );
}
protected function optimalOrder() {
return 'random';
}
/**
* @see JobQueue::doIsEmpty()
* @return bool
*/
protected function doIsEmpty() {
global $wgMemc;
$key = $this->getCacheKey( 'empty' );
$isEmpty = $wgMemc->get( $key );
if ( $isEmpty === 'true' ) {
return true;
} elseif ( $isEmpty === 'false' ) {
return false;
}
list( $dbr, $scope ) = $this->getSlaveDB();
$found = $dbr->selectField( // unclaimed job
'job', '1', array( 'job_cmd' => $this->type, 'job_token' => '' ), __METHOD__
);
$wgMemc->add( $key, $found ? 'false' : 'true', self::CACHE_TTL_LONG );
return !$found;
}
/**
* @see JobQueue::doGetSize()
* @return integer
*/
protected function doGetSize() {
global $wgMemc;
$key = $this->getCacheKey( 'size' );
$size = $wgMemc->get( $key );
if ( is_int( $size ) ) {
return $size;
}
list( $dbr, $scope ) = $this->getSlaveDB();
$size = (int)$dbr->selectField( 'job', 'COUNT(*)',
array( 'job_cmd' => $this->type, 'job_token' => '' ),
__METHOD__
);
$wgMemc->set( $key, $size, self::CACHE_TTL_SHORT );
return $size;
}
/**
* @see JobQueue::doGetAcquiredCount()
* @return integer
*/
protected function doGetAcquiredCount() {
global $wgMemc;
if ( $this->claimTTL <= 0 ) {
return 0; // no acknowledgements
}
$key = $this->getCacheKey( 'acquiredcount' );
$count = $wgMemc->get( $key );
if ( is_int( $count ) ) {
return $count;
}
list( $dbr, $scope ) = $this->getSlaveDB();
$count = (int)$dbr->selectField( 'job', 'COUNT(*)',
array( 'job_cmd' => $this->type, "job_token != {$dbr->addQuotes( '' )}" ),
__METHOD__
);
$wgMemc->set( $key, $count, self::CACHE_TTL_SHORT );
return $count;
}
/**
* @see JobQueue::doBatchPush()
* @param array $jobs
* @param $flags
* @throws DBError|Exception
* @return bool
*/
protected function doBatchPush( array $jobs, $flags ) {
if ( count( $jobs ) ) {
list( $dbw, $scope ) = $this->getMasterDB();
$rowSet = array(); // (sha1 => job) map for jobs that are de-duplicated
$rowList = array(); // list of jobs for jobs that are are not de-duplicated
foreach ( $jobs as $job ) {
$row = $this->insertFields( $job );
if ( $job->ignoreDuplicates() ) {
$rowSet[$row['job_sha1']] = $row;
} else {
$rowList[] = $row;
}
}
$key = $this->getCacheKey( 'empty' );
$atomic = ( $flags & self::QoS_Atomic );
$dbw->onTransactionIdle(
function() use ( $dbw, $rowSet, $rowList, $atomic, $key, $scope
) {
global $wgMemc;
if ( $atomic ) {
$dbw->begin( __METHOD__ ); // wrap all the job additions in one transaction
}
try {
// Strip out any duplicate jobs that are already in the queue...
if ( count( $rowSet ) ) {
$res = $dbw->select( 'job', 'job_sha1',
array(
// No job_type condition since it's part of the job_sha1 hash
'job_sha1' => array_keys( $rowSet ),
'job_token' => '' // unclaimed
),
__METHOD__
);
foreach ( $res as $row ) {
wfDebug( "Job with hash '{$row->job_sha1}' is a duplicate." );
unset( $rowSet[$row->job_sha1] ); // already enqueued
}
}
// Build the full list of job rows to insert
$rows = array_merge( $rowList, array_values( $rowSet ) );
// Insert the job rows in chunks to avoid slave lag...
foreach ( array_chunk( $rows, 50 ) as $rowBatch ) {
$dbw->insert( 'job', $rowBatch, __METHOD__ );
}
wfIncrStats( 'job-insert', count( $rows ) );
wfIncrStats( 'job-insert-duplicate',
count( $rowSet ) + count( $rowList ) - count( $rows ) );
} catch ( DBError $e ) {
if ( $atomic ) {
$dbw->rollback( __METHOD__ );
}
throw $e;
}
if ( $atomic ) {
$dbw->commit( __METHOD__ );
}
$wgMemc->set( $key, 'false', JobQueueDB::CACHE_TTL_LONG );
} );
}
return true;
}
/**
* @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;
}
/**
* Reserve a row with a single UPDATE without holding row locks over RTTs...
*
* @param string $uuid 32 char hex string
* @param $rand integer Random unsigned integer (31 bits)
* @param bool $gte Search for job_random >= $random (otherwise job_random <= $random)
* @return Row|false
*/
protected function claimRandom( $uuid, $rand, $gte ) {
global $wgMemc;
list( $dbw, $scope ) = $this->getMasterDB();
// Check cache to see if the queue has <= OFFSET items
$tinyQueue = $wgMemc->get( $this->getCacheKey( 'small' ) );
$row = false; // the row acquired
$invertedDirection = false; // whether one job_random direction was already scanned
// This uses a replication safe method for acquiring jobs. One could use UPDATE+LIMIT
// instead, but that either uses ORDER BY (in which case it deadlocks in MySQL) or is
// not replication safe. Due to http://bugs.mysql.com/bug.php?id=6980, subqueries cannot
// be used here with MySQL.
do {
if ( $tinyQueue ) { // queue has <= MAX_OFFSET rows
// For small queues, using OFFSET will overshoot and return no rows more often.
// Instead, this uses job_random to pick a row (possibly checking both directions).
$ineq = $gte ? '>=' : '<=';
$dir = $gte ? 'ASC' : 'DESC';
$row = $dbw->selectRow( 'job', '*', // find a random job
array(
'job_cmd' => $this->type,
'job_token' => '', // unclaimed
"job_random {$ineq} {$dbw->addQuotes( $rand )}" ),
__METHOD__,
array( 'ORDER BY' => "job_random {$dir}" )
);
if ( !$row && !$invertedDirection ) {
$gte = !$gte;
$invertedDirection = true;
continue; // try the other direction
}
} else { // table *may* have >= MAX_OFFSET rows
// Bug 42614: "ORDER BY job_random" with a job_random inequality causes high CPU
// in MySQL if there are many rows for some reason. This uses a small OFFSET
// instead of job_random for reducing excess claim retries.
$row = $dbw->selectRow( 'job', '*', // find a random job
array(
'job_cmd' => $this->type,
'job_token' => '', // unclaimed
),
__METHOD__,
array( 'OFFSET' => mt_rand( 0, self::MAX_OFFSET ) )
);
if ( !$row ) {
$tinyQueue = true; // we know the queue must have <= MAX_OFFSET rows
$wgMemc->set( $this->getCacheKey( 'small' ), 1, 30 );
continue; // use job_random
}
}
if ( $row ) { // claim the job
$dbw->update( 'job', // update by PK
array(
'job_token' => $uuid,
'job_token_timestamp' => $dbw->timestamp(),
'job_attempts = job_attempts+1' ),
array( 'job_cmd' => $this->type, 'job_id' => $row->job_id, 'job_token' => '' ),
__METHOD__
);
// This might get raced out by another runner when claiming the previously
// selected row. The use of job_random should minimize this problem, however.
if ( !$dbw->affectedRows() ) {
$row = false; // raced out
}
} else {
break; // nothing to do
}
} while ( !$row );
return $row;
}
/**
* Reserve a row with a single UPDATE without holding row locks over RTTs...
*
* @param string $uuid 32 char hex string
* @return Row|false
*/
protected function claimOldest( $uuid ) {
list( $dbw, $scope ) = $this->getMasterDB();
$row = false; // the row acquired
do {
if ( $dbw->getType() === 'mysql' ) {
// Per http://bugs.mysql.com/bug.php?id=6980, we can't use subqueries on the
// same table being changed in an UPDATE query in MySQL (gives Error: 1093).
// Oracle and Postgre have no such limitation. However, MySQL offers an
// alternative here by supporting ORDER BY + LIMIT for UPDATE queries.
$dbw->query( "UPDATE {$dbw->tableName( 'job' )} " .
"SET " .
"job_token = {$dbw->addQuotes( $uuid ) }, " .
"job_token_timestamp = {$dbw->addQuotes( $dbw->timestamp() )}, " .
"job_attempts = job_attempts+1 " .
"WHERE ( " .
"job_cmd = {$dbw->addQuotes( $this->type )} " .
"AND job_token = {$dbw->addQuotes( '' )} " .
") ORDER BY job_id ASC LIMIT 1",
__METHOD__
);
} else {
// Use a subquery to find the job, within an UPDATE to claim it.
// This uses as much of the DB wrapper functions as possible.
$dbw->update( 'job',
array(
'job_token' => $uuid,
'job_token_timestamp' => $dbw->timestamp(),
'job_attempts = job_attempts+1' ),
array( 'job_id = (' .
$dbw->selectSQLText( 'job', 'job_id',
array( 'job_cmd' => $this->type, 'job_token' => '' ),
__METHOD__,
array( 'ORDER BY' => 'job_id ASC', 'LIMIT' => 1 ) ) .
')'
),
__METHOD__
);
}
// Fetch any row that we just reserved...
if ( $dbw->affectedRows() ) {
$row = $dbw->selectRow( 'job', '*',
array( 'job_cmd' => $this->type, 'job_token' => $uuid ), __METHOD__
);
if ( !$row ) { // raced out by duplicate job removal
wfDebugLog( 'JobQueueDB', "Row deleted as duplicate by another process." );
}
} else {
break; // nothing to do
}
} while ( !$row );
return $row;
}
/**
* Recycle or destroy any jobs that have been claimed for too long
*
* @return integer Number of jobs recycled/deleted
*/
public function recycleAndDeleteStaleJobs() {
global $wgMemc;
$now = time();
list( $dbw, $scope ) = $this->getMasterDB();
$count = 0; // affected rows
if ( !$dbw->lock( "jobqueue-recycle-{$this->type}", __METHOD__, 1 ) ) {
return $count; // already in progress
}
// Remove claims on jobs acquired for too long if enabled...
if ( $this->claimTTL > 0 ) {
$claimCutoff = $dbw->timestamp( $now - $this->claimTTL );
// Get the IDs of jobs that have be claimed but not finished after too long.
// These jobs can be recycled into the queue by expiring the claim. Selecting
// the IDs first means that the UPDATE can be done by primary key (less deadlocks).
$res = $dbw->select( 'job', 'job_id',
array(
'job_cmd' => $this->type,
"job_token != {$dbw->addQuotes( '' )}", // was acquired
"job_token_timestamp < {$dbw->addQuotes( $claimCutoff )}", // stale
"job_attempts < {$dbw->addQuotes( $this->maxTries )}" ), // retries left
__METHOD__
);
$ids = array_map( function( $o ) { return $o->job_id; }, iterator_to_array( $res ) );
if ( count( $ids ) ) {
// Reset job_token for these jobs so that other runners will pick them up.
// Set the timestamp to the current time, as it is useful to now that the job
// was already tried before (the timestamp becomes the "released" time).
$dbw->update( 'job',
array(
'job_token' => '',
'job_token_timestamp' => $dbw->timestamp( $now ) ), // time of release
array(
'job_id' => $ids ),
__METHOD__
);
$count += $dbw->affectedRows();
wfIncrStats( 'job-recycle', $dbw->affectedRows() );
$wgMemc->set( $this->getCacheKey( 'empty' ), 'false', self::CACHE_TTL_LONG );
}
}
// Just destroy any stale jobs...
$pruneCutoff = $dbw->timestamp( $now - self::MAX_AGE_PRUNE );
$conds = array(
'job_cmd' => $this->type,
"job_token != {$dbw->addQuotes( '' )}", // was acquired
"job_token_timestamp < {$dbw->addQuotes( $pruneCutoff )}" // stale
);
if ( $this->claimTTL > 0 ) { // only prune jobs attempted too many times...
$conds[] = "job_attempts >= {$dbw->addQuotes( $this->maxTries )}";
}
// Get the IDs of jobs that are considered stale and should be removed. Selecting
// the IDs first means that the UPDATE can be done by primary key (less deadlocks).
$res = $dbw->select( 'job', 'job_id', $conds, __METHOD__ );
$ids = array_map( function( $o ) { return $o->job_id; }, iterator_to_array( $res ) );
if ( count( $ids ) ) {
$dbw->delete( 'job', array( 'job_id' => $ids ), __METHOD__ );
$count += $dbw->affectedRows();
}
$dbw->unlock( "jobqueue-recycle-{$this->type}", __METHOD__ );
return $count;
}
/**
* @see JobQueue::doAck()
* @param Job $job
* @throws MWException
* @return Job|bool
*/
protected function doAck( Job $job ) {
if ( !$job->getId() ) {
throw new MWException( "Job of type '{$job->getType()}' has no ID." );
}
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
} );
// Delete a row with a single DELETE without holding row locks over RTTs...
$dbw->delete( 'job',
array( 'job_cmd' => $this->type, 'job_id' => $job->getId() ), __METHOD__ );
return true;
}
/**
* @see JobQueue::doDeduplicateRootJob()
* @param Job $job
* @throws MWException
* @return bool
*/
protected function doDeduplicateRootJob( Job $job ) {
$params = $job->getParams();
if ( !isset( $params['rootJobSignature'] ) ) {
throw new MWException( "Cannot register root job; missing 'rootJobSignature'." );
} elseif ( !isset( $params['rootJobTimestamp'] ) ) {
throw new MWException( "Cannot register root job; missing 'rootJobTimestamp'." );
}
$key = $this->getRootJobCacheKey( $params['rootJobSignature'] );
// Callers should call batchInsert() and then this function so that if the insert
// fails, the de-duplication registration will be aborted. Since the insert is
// deferred till "transaction idle", do the same here, so that the ordering is
// maintained. Having only the de-duplication registration succeed would cause
// jobs to become no-ops without any actual jobs that made them redundant.
list( $dbw, $scope ) = $this->getMasterDB();
$dbw->onTransactionIdle( function() use ( $params, $key, $scope ) {
global $wgMemc;
$timestamp = $wgMemc->get( $key ); // current last timestamp of this job
if ( $timestamp && $timestamp >= $params['rootJobTimestamp'] ) {
return true; // a newer version of this root job was enqueued
}
// Update the timestamp of the last root job started at the location...
return $wgMemc->set( $key, $params['rootJobTimestamp'], JobQueueDB::ROOTJOB_TTL );
} );
return true;
}
/**
* Check if the "root" job of a given job has been superseded by a newer one
*
* @param $job Job
* @return bool
*/
protected function isRootJobOldDuplicate( Job $job ) {
global $wgMemc;
$params = $job->getParams();
if ( !isset( $params['rootJobSignature'] ) ) {
return false; // job has no de-deplication info
} elseif ( !isset( $params['rootJobTimestamp'] ) ) {
trigger_error( "Cannot check root job; missing 'rootJobTimestamp'." );
return false;
}
// Get the last time this root job was enqueued
$timestamp = $wgMemc->get( $this->getRootJobCacheKey( $params['rootJobSignature'] ) );
// Check if a new root job was started at the location after this one's...
return ( $timestamp && $timestamp > $params['rootJobTimestamp'] );
}
/**
* @see JobQueue::doWaitForBackups()
* @return void
*/
protected function doWaitForBackups() {
wfWaitForSlaves();
}
/**
* @return Array
*/
protected function doGetPeriodicTasks() {
return array(
'recycleAndDeleteStaleJobs' => array(
'callback' => array( $this, 'recycleAndDeleteStaleJobs' ),
'period' => ceil( $this->claimTTL / 2 )
)
);
}
/**
* @return void
*/
protected function doFlushCaches() {
global $wgMemc;
foreach ( array( 'empty', 'size', 'acquiredcount' ) as $type ) {
$wgMemc->delete( $this->getCacheKey( $type ) );
}
}
/**
* @see JobQueue::getAllQueuedJobs()
* @return Iterator
*/
public function getAllQueuedJobs() {
list( $dbr, $scope ) = $this->getSlaveDB();
return new MappedIterator(
$dbr->select( 'job', '*', array( 'job_cmd' => $this->getType(), 'job_token' => '' ) ),
function( $row ) use ( $scope ) {
$job = Job::factory(
$row->job_cmd,
Title::makeTitle( $row->job_namespace, $row->job_title ),
strlen( $row->job_params ) ? unserialize( $row->job_params ) : false,
$row->job_id
);
$job->id = $row->job_id; // XXX: work around broken subclasses
return $job;
}
);
}
/**
* @return Array (DatabaseBase, ScopedCallback)
*/
protected function getSlaveDB() {
return $this->getDB( DB_SLAVE );
}
/**
* @return Array (DatabaseBase, ScopedCallback)
*/
protected function getMasterDB() {
return $this->getDB( DB_MASTER );
}
/**
* @param $index integer (DB_SLAVE/DB_MASTER)
* @return Array (DatabaseBase, ScopedCallback)
*/
protected function getDB( $index ) {
$lb = ( $this->cluster !== false )
? wfGetLBFactory()->getExternalLB( $this->cluster, $this->wiki )
: wfGetLB( $this->wiki );
$conn = $lb->getConnection( $index, array(), $this->wiki );
return array(
$conn,
new ScopedCallback( function() use ( $lb, $conn ) {
$lb->reuseConnection( $conn );
} )
);
}
/**
* @param $job Job
* @return array
*/
protected function insertFields( Job $job ) {
list( $dbw, $scope ) = $this->getMasterDB();
return array(
// Fields that describe the nature of the job
'job_cmd' => $job->getType(),
'job_namespace' => $job->getTitle()->getNamespace(),
'job_title' => $job->getTitle()->getDBkey(),
'job_params' => self::makeBlob( $job->getParams() ),
// Additional job metadata
'job_id' => $dbw->nextSequenceValue( 'job_job_id_seq' ),
'job_timestamp' => $dbw->timestamp(),
'job_sha1' => wfBaseConvert(
sha1( serialize( $job->getDeduplicationInfo() ) ),
16, 36, 31
),
'job_random' => mt_rand( 0, self::MAX_JOB_RANDOM )
);
}
/**
* @return string
*/
private function getCacheKey( $property ) {
list( $db, $prefix ) = wfSplitWikiID( $this->wiki );
return wfForeignMemcKey( $db, $prefix, 'jobqueue', $this->type, $property );
}
/**
* @param string $signature Hash identifier of the root job
* @return string
*/
private function getRootJobCacheKey( $signature ) {
list( $db, $prefix ) = wfSplitWikiID( $this->wiki );
return wfForeignMemcKey( $db, $prefix, 'jobqueue', $this->type, 'rootjob', $signature );
}
/**
* @param $params
* @return string
*/
protected static function makeBlob( $params ) {
if ( $params !== false ) {
return serialize( $params );
} else {
return '';
}
}
/**
* @param $blob
* @return bool|mixed
*/
protected static function extractBlob( $blob ) {
if ( (string)$blob !== '' ) {
return unserialize( $blob );
} else {
return false;
}
}
}