Current File : /www/varak.net/wiki.varak.net/includes/deferred/DeferredUpdates.php
<?php
/**
* Interface and manager for deferred updates.
*
* 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 Wikimedia\Rdbms\IDatabase;
use MediaWiki\MediaWikiServices;
use Wikimedia\Rdbms\LBFactory;
use Wikimedia\Rdbms\LoadBalancer;
/**
* Class for managing the deferred updates
*
* In web request mode, deferred updates can be run at the end of the request, either before or
* after the HTTP response has been sent. In either case, they run after the DB commit step. If
* an update runs after the response is sent, it will not block clients. If sent before, it will
* run synchronously. These two modes are defined via PRESEND and POSTSEND constants, the latter
* being the default for addUpdate() and addCallableUpdate().
*
* Updates that work through this system will be more likely to complete by the time the client
* makes their next request after this one than with the JobQueue system.
*
* In CLI mode, deferred updates will run:
* - a) During DeferredUpdates::addUpdate if no LBFactory DB handles have writes pending
* - b) On commit of an LBFactory DB handle if no other such handles have writes pending
* - c) During an LBFactory::waitForReplication call if no LBFactory DBs have writes pending
* - d) When the queue is large and an LBFactory DB handle commits (EnqueueableDataUpdate only)
* - e) At the completion of Maintenance::execute()
*
* @see Maintenance::setLBFactoryTriggers
*
* When updates are deferred, they go into one two FIFO "top-queues" (one for pre-send and one
* for post-send). Updates enqueued *during* doUpdate() of a "top" update go into the "sub-queue"
* for that update. After that method finishes, the sub-queue is run until drained. This continues
* for each top-queue job until the entire top queue is drained. This happens for the pre-send
* top-queue, and later on, the post-send top-queue, in execute().
*
* @since 1.19
*/
class DeferredUpdates {
/** @var DeferrableUpdate[] Updates to be deferred until before request end */
private static $preSendUpdates = [];
/** @var DeferrableUpdate[] Updates to be deferred until after request end */
private static $postSendUpdates = [];
const ALL = 0; // all updates; in web requests, use only after flushing the output buffer
const PRESEND = 1; // for updates that should run before flushing output buffer
const POSTSEND = 2; // for updates that should run after flushing output buffer
const BIG_QUEUE_SIZE = 100;
/** @var array|null Information about the current execute() call or null if not running */
private static $executeContext;
/**
* Add an update to the deferred list to be run later by execute()
*
* In CLI mode, callback magic will also be used to run updates when safe
*
* @param DeferrableUpdate $update Some object that implements doUpdate()
* @param int $stage DeferredUpdates constant (PRESEND or POSTSEND) (since 1.27)
*/
public static function addUpdate( DeferrableUpdate $update, $stage = self::POSTSEND ) {
global $wgCommandLineMode;
if (
self::$executeContext &&
self::$executeContext['stage'] >= $stage &&
!( $update instanceof MergeableUpdate )
) {
// This is a sub-DeferredUpdate; run it right after its parent update.
// Also, while post-send updates are running, push any "pre-send" jobs to the
// active post-send queue to make sure they get run this round (or at all).
self::$executeContext['subqueue'][] = $update;
return;
}
if ( $stage === self::PRESEND ) {
self::push( self::$preSendUpdates, $update );
} else {
self::push( self::$postSendUpdates, $update );
}
// Try to run the updates now if in CLI mode and no transaction is active.
// This covers scripts that don't/barely use the DB but make updates to other stores.
if ( $wgCommandLineMode ) {
self::tryOpportunisticExecute( 'run' );
}
}
/**
* Add a callable update. In a lot of cases, we just need a callback/closure,
* defining a new DeferrableUpdate object is not necessary
*
* @see MWCallableUpdate::__construct()
*
* @param callable $callable
* @param int $stage DeferredUpdates constant (PRESEND or POSTSEND) (since 1.27)
* @param IDatabase|IDatabase[]|null $dbw Abort if this DB is rolled back [optional] (since 1.28)
*/
public static function addCallableUpdate(
$callable, $stage = self::POSTSEND, $dbw = null
) {
self::addUpdate( new MWCallableUpdate( $callable, wfGetCaller(), $dbw ), $stage );
}
/**
* Do any deferred updates and clear the list
*
* @param string $mode Use "enqueue" to use the job queue when possible [Default: "run"]
* @param int $stage DeferredUpdates constant (PRESEND, POSTSEND, or ALL) (since 1.27)
*/
public static function doUpdates( $mode = 'run', $stage = self::ALL ) {
$stageEffective = ( $stage === self::ALL ) ? self::POSTSEND : $stage;
// For ALL mode, make sure that any PRESEND updates added along the way get run.
// Normally, these use the subqueue, but that isn't true for MergeableUpdate items.
do {
if ( $stage === self::ALL || $stage === self::PRESEND ) {
self::execute( self::$preSendUpdates, $mode, $stageEffective );
}
if ( $stage === self::ALL || $stage == self::POSTSEND ) {
self::execute( self::$postSendUpdates, $mode, $stageEffective );
}
} while ( $stage === self::ALL && self::$preSendUpdates );
}
/**
* @param DeferrableUpdate[] $queue
* @param DeferrableUpdate $update
*/
private static function push( array &$queue, DeferrableUpdate $update ) {
if ( $update instanceof MergeableUpdate ) {
$class = get_class( $update ); // fully-qualified class
if ( isset( $queue[$class] ) ) {
/** @var MergeableUpdate $existingUpdate */
$existingUpdate = $queue[$class];
$existingUpdate->merge( $update );
// Move the update to the end to handle things like mergeable purge
// updates that might depend on the prior updates in the queue running
unset( $queue[$class] );
$queue[$class] = $existingUpdate;
} else {
$queue[$class] = $update;
}
} else {
$queue[] = $update;
}
}
/**
* Immediately run/queue a list of updates
*
* @param DeferrableUpdate[] &$queue List of DeferrableUpdate objects
* @param string $mode Use "enqueue" to use the job queue when possible
* @param int $stage Class constant (PRESEND, POSTSEND) (since 1.28)
* @throws ErrorPageError Happens on top-level calls
* @throws Exception Happens on second-level calls
*/
protected static function execute( array &$queue, $mode, $stage ) {
$services = MediaWikiServices::getInstance();
$stats = $services->getStatsdDataFactory();
$lbFactory = $services->getDBLoadBalancerFactory();
$method = RequestContext::getMain()->getRequest()->getMethod();
$ticket = $lbFactory->getEmptyTransactionTicket( __METHOD__ );
/** @var ErrorPageError $reportableError */
$reportableError = null;
/** @var DeferrableUpdate[] $updates Snapshot of queue */
$updates = $queue;
// Keep doing rounds of updates until none get enqueued...
while ( $updates ) {
$queue = []; // clear the queue
// Order will be DataUpdate followed by generic DeferrableUpdate tasks
$updatesByType = [ 'data' => [], 'generic' => [] ];
foreach ( $updates as $du ) {
if ( $du instanceof DataUpdate ) {
$du->setTransactionTicket( $ticket );
$updatesByType['data'][] = $du;
} else {
$updatesByType['generic'][] = $du;
}
$name = ( $du instanceof DeferrableCallback )
? get_class( $du ) . '-' . $du->getOrigin()
: get_class( $du );
$stats->increment( 'deferred_updates.' . $method . '.' . $name );
}
// Execute all remaining tasks...
foreach ( $updatesByType as $updatesForType ) {
foreach ( $updatesForType as $update ) {
self::$executeContext = [ 'stage' => $stage, 'subqueue' => [] ];
try {
/** @var DeferrableUpdate $update */
$guiError = self::runUpdate( $update, $lbFactory, $mode, $stage );
$reportableError = $reportableError ?: $guiError;
// Do the subqueue updates for $update until there are none
while ( self::$executeContext['subqueue'] ) {
$subUpdate = reset( self::$executeContext['subqueue'] );
$firstKey = key( self::$executeContext['subqueue'] );
unset( self::$executeContext['subqueue'][$firstKey] );
if ( $subUpdate instanceof DataUpdate ) {
$subUpdate->setTransactionTicket( $ticket );
}
$guiError = self::runUpdate( $subUpdate, $lbFactory, $mode, $stage );
$reportableError = $reportableError ?: $guiError;
}
} finally {
// Make sure we always clean up the context.
// Losing updates while rewinding the stack is acceptable,
// losing updates that are added later is not.
self::$executeContext = null;
}
}
}
$updates = $queue; // new snapshot of queue (check for new entries)
}
if ( $reportableError ) {
throw $reportableError; // throw the first of any GUI errors
}
}
/**
* @param DeferrableUpdate $update
* @param LBFactory $lbFactory
* @param string $mode
* @param int $stage
* @return ErrorPageError|null
*/
private static function runUpdate(
DeferrableUpdate $update, LBFactory $lbFactory, $mode, $stage
) {
$guiError = null;
try {
if ( $mode === 'enqueue' && $update instanceof EnqueueableDataUpdate ) {
// Run only the job enqueue logic to complete the update later
$spec = $update->getAsJobSpecification();
JobQueueGroup::singleton( $spec['wiki'] )->push( $spec['job'] );
} elseif ( $update instanceof TransactionRoundDefiningUpdate ) {
$update->doUpdate();
} else {
// Run the bulk of the update now
$fnameTrxOwner = get_class( $update ) . '::doUpdate';
$lbFactory->beginMasterChanges( $fnameTrxOwner );
$update->doUpdate();
$lbFactory->commitMasterChanges( $fnameTrxOwner );
}
} catch ( Exception $e ) {
// Reporting GUI exceptions does not work post-send
if ( $e instanceof ErrorPageError && $stage === self::PRESEND ) {
$guiError = $e;
}
MWExceptionHandler::rollbackMasterChangesAndLog( $e );
// VW-style hack to work around T190178, so we can make sure
// PageMetaDataUpdater doesn't throw exceptions.
if ( defined( 'MW_PHPUNIT_TEST' ) ) {
throw $e;
}
}
return $guiError;
}
/**
* Run all deferred updates immediately if there are no DB writes active
*
* If there are many deferred updates pending, $mode is 'run', and there
* are still busy LBFactory database handles, then any EnqueueableDataUpdate
* tasks might be enqueued as jobs to be executed later.
*
* @param string $mode Use "enqueue" to use the job queue when possible
* @return bool Whether updates were allowed to run
* @since 1.28
*/
public static function tryOpportunisticExecute( $mode = 'run' ) {
// execute() loop is already running
if ( self::$executeContext ) {
return false;
}
// Avoiding running updates without them having outer scope
if ( !self::areDatabaseTransactionsActive() ) {
self::doUpdates( $mode );
return true;
}
if ( self::pendingUpdatesCount() >= self::BIG_QUEUE_SIZE ) {
// If we cannot run the updates with outer transaction context, try to
// at least enqueue all the updates that support queueing to job queue
self::$preSendUpdates = self::enqueueUpdates( self::$preSendUpdates );
self::$postSendUpdates = self::enqueueUpdates( self::$postSendUpdates );
}
return !self::pendingUpdatesCount();
}
/**
* Enqueue a job for each EnqueueableDataUpdate item and return the other items
*
* @param DeferrableUpdate[] $updates A list of deferred update instances
* @return DeferrableUpdate[] Remaining updates that do not support being queued
*/
private static function enqueueUpdates( array $updates ) {
$remaining = [];
foreach ( $updates as $update ) {
if ( $update instanceof EnqueueableDataUpdate ) {
$spec = $update->getAsJobSpecification();
JobQueueGroup::singleton( $spec['wiki'] )->push( $spec['job'] );
} else {
$remaining[] = $update;
}
}
return $remaining;
}
/**
* @return int Number of enqueued updates
* @since 1.28
*/
public static function pendingUpdatesCount() {
return count( self::$preSendUpdates ) + count( self::$postSendUpdates );
}
/**
* @param int $stage DeferredUpdates constant (PRESEND, POSTSEND, or ALL)
* @return DeferrableUpdate[]
* @since 1.29
*/
public static function getPendingUpdates( $stage = self::ALL ) {
$updates = [];
if ( $stage === self::ALL || $stage === self::PRESEND ) {
$updates = array_merge( $updates, self::$preSendUpdates );
}
if ( $stage === self::ALL || $stage === self::POSTSEND ) {
$updates = array_merge( $updates, self::$postSendUpdates );
}
return $updates;
}
/**
* Clear all pending updates without performing them. Generally, you don't
* want or need to call this. Unit tests need it though.
*/
public static function clearPendingUpdates() {
self::$preSendUpdates = [];
self::$postSendUpdates = [];
}
/**
* @return bool If a transaction round is active or connection is not ready for commit()
*/
private static function areDatabaseTransactionsActive() {
$lbFactory = MediaWikiServices::getInstance()->getDBLoadBalancerFactory();
if ( $lbFactory->hasTransactionRound() || !$lbFactory->isReadyForRoundOperations() ) {
return true;
}
$connsBusy = false;
$lbFactory->forEachLB( function ( LoadBalancer $lb ) use ( &$connsBusy ) {
$lb->forEachOpenMasterConnection( function ( IDatabase $conn ) use ( &$connsBusy ) {
if ( $conn->writesOrCallbacksPending() || $conn->explicitTrxActive() ) {
$connsBusy = true;
}
} );
} );
return $connsBusy;
}
}
Mini Shell