includes/jobqueue/JobRunner.php
<?php
/**
* 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
*/
use Liuggio\StatsdClient\Factory\StatsdDataFactoryInterface;
use MediaWiki\Cache\LinkCache;
use MediaWiki\Config\ServiceOptions;
use MediaWiki\Deferred\DeferredUpdates;
use MediaWiki\Http\Telemetry;
use MediaWiki\MainConfigNames;
use Psr\Log\LoggerInterface;
use Wikimedia\Rdbms\DBConnectionError;
use Wikimedia\Rdbms\DBReadOnlyError;
use Wikimedia\Rdbms\ILBFactory;
use Wikimedia\Rdbms\ReadOnlyMode;
/**
* Job queue runner utility methods.
*
* @since 1.24
* @ingroup JobQueue
*/
class JobRunner {
/**
* @internal For use by ServiceWiring
*/
public const CONSTRUCTOR_OPTIONS = [
MainConfigNames::JobBackoffThrottling,
MainConfigNames::JobClasses,
MainConfigNames::MaxJobDBWriteDuration,
MainConfigNames::TrxProfilerLimits,
];
/** @var ServiceOptions */
private $options;
/** @var ILBFactory */
private $lbFactory;
/** @var JobQueueGroup */
private $jobQueueGroup;
/** @var ReadOnlyMode */
private $readOnlyMode;
/** @var LinkCache */
private $linkCache;
/** @var StatsdDataFactoryInterface */
private $stats;
/** @var callable|null Debug output handler */
private $debug;
/** @var LoggerInterface */
private $logger;
/** @var int Abort if more than this much DB lag is present */
private const MAX_ALLOWED_LAG = 3;
/** @var int An appropriate timeout to balance lag avoidance and job progress */
private const SYNC_TIMEOUT = self::MAX_ALLOWED_LAG;
/** @var float Check replica DB lag this many seconds */
private const LAG_CHECK_PERIOD = 1.0;
/** @var int Seconds to back off a queue due to errors */
private const ERROR_BACKOFF_TTL = 1;
/** @var int Seconds to back off a queue due to read-only errors */
private const READONLY_BACKOFF_TTL = 30;
/**
* @param callable $debug Optional debug output handler
*/
public function setDebugHandler( $debug ) {
$this->debug = $debug;
}
/**
* @internal For use by ServiceWiring
* @param ServiceOptions $serviceOptions
* @param ILBFactory $lbFactory
* @param JobQueueGroup $jobQueueGroup The JobQueueGroup for this wiki
* @param ReadOnlyMode $readOnlyMode
* @param LinkCache $linkCache
* @param StatsdDataFactoryInterface $statsdDataFactory
* @param LoggerInterface $logger
*/
public function __construct(
ServiceOptions $serviceOptions,
ILBFactory $lbFactory,
JobQueueGroup $jobQueueGroup,
ReadOnlyMode $readOnlyMode,
LinkCache $linkCache,
StatsdDataFactoryInterface $statsdDataFactory,
LoggerInterface $logger
) {
$serviceOptions->assertRequiredOptions( self::CONSTRUCTOR_OPTIONS );
$this->options = $serviceOptions;
$this->lbFactory = $lbFactory;
$this->jobQueueGroup = $jobQueueGroup;
$this->readOnlyMode = $readOnlyMode;
$this->linkCache = $linkCache;
$this->stats = $statsdDataFactory;
$this->logger = $logger;
}
/**
* Run jobs of the specified number/type for the specified time
*
* The response map has a 'job' field that lists status of each job, including:
* - type : the job/queue type
* - status : ok/failed
* - error : any error message string
* - time : the job run time in ms
* The response map also has:
* - backoffs : the (job/queue type => seconds) map of backoff times
* - elapsed : the total time spent running tasks in ms
* - reached : the reason the script finished, one of (none-ready, job-limit, time-limit,
* memory-limit, exception)
*
* This method outputs status information only if a debug handler was set.
* Any exceptions are caught and logged, but are not reported as output.
*
* @param array $options Map of parameters:
* - type : specified job/queue type (or false for the default types)
* - maxJobs : maximum number of jobs to run
* - maxTime : maximum time in seconds before stopping
* - throttle : whether to respect job backoff configuration
* @return array Summary response that can easily be JSON serialized
* @throws JobQueueError
*/
public function run( array $options ) {
$type = $options['type'] ?? false;
$maxJobs = $options['maxJobs'] ?? false;
$maxTime = $options['maxTime'] ?? false;
$throttle = $options['throttle'] ?? true;
$jobClasses = $this->options->get( MainConfigNames::JobClasses );
$profilerLimits = $this->options->get( MainConfigNames::TrxProfilerLimits );
$response = [ 'jobs' => [], 'reached' => 'none-ready' ];
if ( $type !== false && !isset( $jobClasses[$type] ) ) {
// Invalid job type specified
$response['reached'] = 'none-possible';
return $response;
}
if ( $this->readOnlyMode->isReadOnly() ) {
// Any jobs popped off the queue might fail to run and thus might end up lost
$response['reached'] = 'read-only';
return $response;
}
[ , $maxLag ] = $this->lbFactory->getMainLB()->getMaxLag();
if ( $maxLag >= self::MAX_ALLOWED_LAG ) {
// DB lag is already too high; caller can immediately try other wikis if applicable
$response['reached'] = 'replica-lag-limit';
return $response;
}
// Narrow DB query expectations for this HTTP request
$this->lbFactory->getTransactionProfiler()
->setExpectations( $profilerLimits['JobRunner'], __METHOD__ );
// Error out if an explicit DB transaction round is somehow active
if ( $this->lbFactory->hasTransactionRound() ) {
throw new LogicException( __METHOD__ . ' called with an active transaction round.' );
}
// Some jobs types should not run until a certain timestamp
$backoffs = []; // map of (type => UNIX expiry)
$backoffDeltas = []; // map of (type => seconds)
$wait = 'wait'; // block to read backoffs the first time
$loopStartTime = microtime( true );
$jobsPopped = 0;
$timeMsTotal = 0;
$lastSyncTime = 1; // initialize "last sync check timestamp" to "ages ago"
// Keep popping and running jobs until there are no more...
do {
// Sync the persistent backoffs with concurrent runners
$backoffs = $this->syncBackoffDeltas( $backoffs, $backoffDeltas, $wait );
$backoffKeys = $throttle ? array_keys( $backoffs ) : [];
$wait = 'nowait'; // less important now
if ( $type === false ) {
// Treat the default job type queues as a single queue and pop off a job
$job = $this->jobQueueGroup
->pop( JobQueueGroup::TYPE_DEFAULT, JobQueueGroup::USE_CACHE, $backoffKeys );
} else {
// Pop off a job from the specified job type queue unless the execution of
// that type of job is currently rate-limited by the back-off list
$job = in_array( $type, $backoffKeys ) ? false : $this->jobQueueGroup->pop( $type );
}
if ( $job ) {
++$jobsPopped;
$jType = $job->getType();
// Back off of certain jobs for a while (for throttling and for errors)
$ttw = $this->getBackoffTimeToWait( $job );
if ( $ttw > 0 ) {
// Always add the delta for other runners in case the time running the
// job negated the backoff for each individually but not collectively.
$backoffDeltas[$jType] = ( $backoffDeltas[$jType] ?? 0 ) + $ttw;
$backoffs = $this->syncBackoffDeltas( $backoffs, $backoffDeltas, $wait );
}
$info = $this->executeJob( $job );
// Mark completed or "one shot only" jobs as resolved
if ( $info['status'] !== false || !$job->allowRetries() ) {
$this->jobQueueGroup->ack( $job );
}
// Back off of certain jobs for a while (for throttling and for errors)
if ( $info['status'] === false && mt_rand( 0, 49 ) == 0 ) {
$ttw = max( $ttw, $this->getErrorBackoffTTL( $info['caught'] ) );
$backoffDeltas[$jType] = ( $backoffDeltas[$jType] ?? 0 ) + $ttw;
}
$response['jobs'][] = [
'type' => $jType,
'status' => ( $info['status'] === false ) ? 'failed' : 'ok',
'error' => $info['error'],
'time' => $info['timeMs']
];
$timeMsTotal += $info['timeMs'];
// Break out if we hit the job count or wall time limits
if ( $maxJobs && $jobsPopped >= $maxJobs ) {
$response['reached'] = 'job-limit';
break;
} elseif ( $maxTime && ( microtime( true ) - $loopStartTime ) > $maxTime ) {
$response['reached'] = 'time-limit';
break;
}
// Stop if we caught a DBConnectionError. In theory it would be
// possible to explicitly reconnect, but the present behaviour
// is to just throw more exceptions every time something database-
// related is attempted.
if ( in_array( DBConnectionError::class, $info['caught'], true ) ) {
$response['reached'] = 'exception';
break;
}
// Don't let any of the main DB replica DBs get backed up.
// This only waits for so long before exiting and letting
// other wikis in the farm (on different masters) get a chance.
$timePassed = microtime( true ) - $lastSyncTime;
if ( $timePassed >= self::LAG_CHECK_PERIOD || $timePassed < 0 ) {
$opts = [ 'ifWritesSince' => $lastSyncTime, 'timeout' => self::SYNC_TIMEOUT ];
if ( !$this->lbFactory->waitForReplication( $opts ) ) {
$response['reached'] = 'replica-lag-limit';
break;
}
$lastSyncTime = microtime( true );
}
// Abort if nearing OOM to avoid erroring out in the middle of a job
if ( !$this->checkMemoryOK() ) {
$response['reached'] = 'memory-limit';
break;
}
}
} while ( $job );
// Sync the persistent backoffs for the next runJobs.php pass
if ( $backoffDeltas ) {
$this->syncBackoffDeltas( $backoffs, $backoffDeltas, 'wait' );
}
$response['backoffs'] = $backoffs;
$response['elapsed'] = $timeMsTotal;
return $response;
}
/**
* Run a specific job in a manner appropriate for mass use by job dispatchers
*
* Wraps the job's run() and tearDown() methods into appropriate transaction rounds.
* During execution, SPI-based logging will use the ID of the HTTP request that spawned
* the job (instead of the current one). Large DB write transactions will be subject to
* $wgMaxJobDBWriteDuration.
*
* This should never be called if there are explicit transaction rounds or pending DB writes
*
* @param RunnableJob $job
* @return array Map of:
* - status: boolean; whether the job succeed
* - error: error string; empty if there was no error specified
* - caught: list of FQCNs corresponding to any exceptions caught
* - timeMs: float; job execution time in milliseconds
* @since 1.35
*/
public function executeJob( RunnableJob $job ) {
$telemetry = Telemetry::getInstance();
$oldRequestId = $telemetry->getRequestId();
if ( $job->getRequestId() !== null ) {
// Temporarily inherit the original ID of the web request that spawned this job
$telemetry->overrideRequestId( $job->getRequestId() );
} else {
// TODO: do we need to regenerate if job doesn't have the request id?
// If JobRunner was called with X-Request-ID header, regeneration will generate the
// same value
$telemetry->regenerateRequestId();
}
// Use an appropriate timeout to balance lag avoidance and job progress
$oldTimeout = $this->lbFactory->setDefaultReplicationWaitTimeout( self::SYNC_TIMEOUT );
try {
return $this->doExecuteJob( $job );
} finally {
$this->lbFactory->setDefaultReplicationWaitTimeout( $oldTimeout );
$telemetry->overrideRequestId( $oldRequestId );
}
}
/**
* @param RunnableJob $job
* @return array Map of:
* - status: boolean; whether the job succeed
* - error: error string; empty if there was no error specified
* - caught: list of FQCNs corresponding to any exceptions caught
* - timeMs: float; job execution time in milliseconds
*/
private function doExecuteJob( RunnableJob $job ) {
$jType = $job->getType();
$msg = $job->toString() . " STARTING";
$this->logger->debug( $msg, [ 'job_type' => $job->getType() ] );
$this->debugCallback( $msg );
// Clear out title cache data from prior snapshots
// (e.g. from before JobRunner was invoked in this process)
$this->linkCache->clear();
// Run the job...
$caught = [];
$rssStart = $this->getMaxRssKb();
$jobStartTime = microtime( true );
try {
$fnameTrxOwner = get_class( $job ) . '::run'; // give run() outer scope
// Flush any pending changes left over from an implicit transaction round
if ( $job->hasExecutionFlag( $job::JOB_NO_EXPLICIT_TRX_ROUND ) ) {
$this->lbFactory->commitPrimaryChanges( $fnameTrxOwner ); // new implicit round
} else {
$this->lbFactory->beginPrimaryChanges( $fnameTrxOwner ); // new explicit round
}
// Clear any stale REPEATABLE-READ snapshots from replica DB connections
$this->lbFactory->flushReplicaSnapshots( $fnameTrxOwner );
$status = $job->run();
$error = $job->getLastError();
// Commit all pending changes from this job
$this->lbFactory->commitPrimaryChanges(
$fnameTrxOwner,
// Abort if any transaction was too big
$this->options->get( MainConfigNames::MaxJobDBWriteDuration )
);
// Run any deferred update tasks; doUpdates() manages transactions itself
DeferredUpdates::doUpdates();
} catch ( Throwable $e ) {
MWExceptionHandler::rollbackPrimaryChangesAndLog( $e );
$status = false;
$error = get_class( $e ) . ': ' . $e->getMessage() . ' in '
. $e->getFile() . ' on line ' . $e->getLine();
$caught[] = get_class( $e );
}
// Always attempt to call teardown(), even if Job throws exception
try {
$job->tearDown( $status );
} catch ( Throwable $e ) {
MWExceptionHandler::logException( $e );
}
$timeMs = intval( ( microtime( true ) - $jobStartTime ) * 1000 );
$rssEnd = $this->getMaxRssKb();
// Record how long jobs wait before getting popped
$readyTs = $job->getReadyTimestamp();
if ( $readyTs ) {
$pickupDelay = max( 0, $jobStartTime - $readyTs );
$this->stats->timing( 'jobqueue.pickup_delay.all', 1000 * $pickupDelay );
$this->stats->timing( "jobqueue.pickup_delay.$jType", 1000 * $pickupDelay );
}
// Record root job age for jobs being run
$rootTimestamp = $job->getRootJobParams()['rootJobTimestamp'];
if ( $rootTimestamp ) {
$age = max( 0, $jobStartTime - (int)wfTimestamp( TS_UNIX, $rootTimestamp ) );
$this->stats->timing( "jobqueue.pickup_root_age.$jType", 1000 * $age );
}
// Track the execution time for jobs
$this->stats->timing( "jobqueue.run.$jType", $timeMs );
// Track RSS increases for jobs (in case of memory leaks)
if ( $rssStart && $rssEnd ) {
$this->stats->updateCount( "jobqueue.rss_delta.$jType", $rssEnd - $rssStart );
}
if ( $status === false ) {
$msg = $job->toString() . " t={job_duration} error={job_error}";
$this->logger->error( $msg, [
'job_type' => $job->getType(),
'job_duration' => $timeMs,
'job_error' => $error,
] );
$msg = $job->toString() . " t=$timeMs error={$error}";
$this->debugCallback( $msg );
} else {
$msg = $job->toString() . " t={job_duration} good";
$this->logger->info( $msg, [
'job_type' => $job->getType(),
'job_duration' => $timeMs,
] );
$msg = $job->toString() . " t=$timeMs good";
$this->debugCallback( $msg );
}
return [
'status' => $status,
'error' => $error,
'caught' => $caught,
'timeMs' => $timeMs
];
}
/**
* @param string[] $caught List of FQCNs corresponding to any exceptions caught
* @return int TTL in seconds
*/
private function getErrorBackoffTTL( array $caught ) {
return in_array( DBReadOnlyError::class, $caught )
? self::READONLY_BACKOFF_TTL
: self::ERROR_BACKOFF_TTL;
}
/**
* @return int|null Max memory RSS in kilobytes
*/
private function getMaxRssKb() {
$info = getrusage( 0 /* RUSAGE_SELF */ );
// see https://linux.die.net/man/2/getrusage
return isset( $info['ru_maxrss'] ) ? (int)$info['ru_maxrss'] : null;
}
/**
* @param RunnableJob $job
* @return int Seconds for this runner to avoid doing more jobs of this type
* @see $wgJobBackoffThrottling
*/
private function getBackoffTimeToWait( RunnableJob $job ) {
$throttling = $this->options->get( MainConfigNames::JobBackoffThrottling );
if ( !isset( $throttling[$job->getType()] ) || $job instanceof DuplicateJob ) {
return 0; // not throttled
}
$itemsPerSecond = $throttling[$job->getType()];
if ( $itemsPerSecond <= 0 ) {
return 0; // not throttled
}
$seconds = 0;
if ( $job->workItemCount() > 0 ) {
$exactSeconds = $job->workItemCount() / $itemsPerSecond;
// use randomized rounding
$seconds = floor( $exactSeconds );
$remainder = $exactSeconds - $seconds;
$seconds += ( mt_rand() / mt_getrandmax() < $remainder ) ? 1 : 0;
}
return (int)$seconds;
}
/**
* Get the previous backoff expiries from persistent storage
* On I/O or lock acquisition failure this returns the original $backoffs.
*
* @param array $backoffs Map of (job type => UNIX timestamp)
* @param string $mode Lock wait mode - "wait" or "nowait"
* @return array Map of (job type => backoff expiry timestamp)
*/
private function loadBackoffs( array $backoffs, $mode = 'wait' ) {
$file = wfTempDir() . '/mw-runJobs-backoffs.json';
if ( is_file( $file ) ) {
$noblock = ( $mode === 'nowait' ) ? LOCK_NB : 0;
$handle = fopen( $file, 'rb' );
if ( !flock( $handle, LOCK_SH | $noblock ) ) {
fclose( $handle );
return $backoffs; // don't wait on lock
}
$content = stream_get_contents( $handle );
flock( $handle, LOCK_UN );
fclose( $handle );
$ctime = microtime( true );
$cBackoffs = json_decode( $content, true ) ?: [];
foreach ( $cBackoffs as $type => $timestamp ) {
if ( $timestamp < $ctime ) {
unset( $cBackoffs[$type] );
}
}
} else {
$cBackoffs = [];
}
return $cBackoffs;
}
/**
* Merge the current backoff expiries from persistent storage
*
* The $deltas map is set to an empty array on success.
* On I/O or lock acquisition failure this returns the original $backoffs.
*
* @param array $backoffs Map of (job type => UNIX timestamp)
* @param array &$deltas Map of (job type => seconds)
* @param string $mode Lock wait mode - "wait" or "nowait"
* @return array The new backoffs account for $backoffs and the latest file data
*/
private function syncBackoffDeltas( array $backoffs, array &$deltas, $mode = 'wait' ) {
if ( !$deltas ) {
return $this->loadBackoffs( $backoffs, $mode );
}
$noblock = ( $mode === 'nowait' ) ? LOCK_NB : 0;
$file = wfTempDir() . '/mw-runJobs-backoffs.json';
$handle = fopen( $file, 'wb+' );
if ( !flock( $handle, LOCK_EX | $noblock ) ) {
fclose( $handle );
return $backoffs; // don't wait on lock
}
$ctime = microtime( true );
$content = stream_get_contents( $handle );
$cBackoffs = json_decode( $content, true ) ?: [];
foreach ( $deltas as $type => $seconds ) {
$cBackoffs[$type] = isset( $cBackoffs[$type] ) && $cBackoffs[$type] >= $ctime
? $cBackoffs[$type] + $seconds
: $ctime + $seconds;
}
foreach ( $cBackoffs as $type => $timestamp ) {
if ( $timestamp < $ctime ) {
unset( $cBackoffs[$type] );
}
}
ftruncate( $handle, 0 );
fwrite( $handle, json_encode( $cBackoffs ) );
flock( $handle, LOCK_UN );
fclose( $handle );
$deltas = [];
return $cBackoffs;
}
/**
* Make sure that this script is not too close to the memory usage limit.
* It is better to die in between jobs than OOM right in the middle of one.
* @return bool
*/
private function checkMemoryOK() {
static $maxBytes = null;
if ( $maxBytes === null ) {
$m = [];
if ( preg_match( '!^(\d+)(k|m|g|)$!i', ini_get( 'memory_limit' ), $m ) ) {
[ , $num, $unit ] = $m;
$conv = [ 'g' => 1073741824, 'm' => 1048576, 'k' => 1024, '' => 1 ];
$maxBytes = (int)$num * $conv[strtolower( $unit )];
} else {
$maxBytes = 0;
}
}
$usedBytes = memory_get_usage();
if ( $maxBytes && $usedBytes >= 0.95 * $maxBytes ) {
$msg = "Detected excessive memory usage ({used_bytes}/{max_bytes}).";
$this->logger->error( $msg, [
'used_bytes' => $usedBytes,
'max_bytes' => $maxBytes,
] );
$msg = "Detected excessive memory usage ($usedBytes/$maxBytes).";
$this->debugCallback( $msg );
return false;
}
return true;
}
/**
* Log the job message
* @param string $msg The message to log
*/
private function debugCallback( $msg ) {
if ( $this->debug ) {
call_user_func_array( $this->debug, [ wfTimestamp( TS_DB ) . " $msg\n" ] );
}
}
}