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<?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
*/
/**
* Interface that deferrable updates should implement. Basically required so we
* can validate input on DeferredUpdates::addUpdate()
*
* @since 1.19
*/
interface DeferrableUpdate {
/**
* Perform the actual work
*/
function doUpdate();
}
/**
* Class for managing the deferred updates
*
* Deferred updates can be run at the end of the request,
* after the HTTP response has been sent. In CLI mode, updates
* are only deferred until there is no local master DB transaction.
* When updates are deferred, they go into a simple FIFO queue.
*
* @since 1.19
*/
class DeferredUpdates {
/**
* @var array Updates to be deferred until the end of the request.
*/
private static $updates = array();
/**
* Add an update to the deferred list
* @param DeferrableUpdate $update Some object that implements doUpdate()
*/
public static function addUpdate( DeferrableUpdate $update ) {
global $wgCommandLineMode;
array_push( self::$updates, $update );
// CLI scripts may forget to periodically flush these updates,
// so try to handle that rather than OOMing and losing them.
// Try to run the updates as soon as there is no local transaction.
static $waitingOnTrx = false; // de-duplicate callback
if ( $wgCommandLineMode && !$waitingOnTrx ) {
$lb = wfGetLB();
$dbw = $lb->getAnyOpenConnection( $lb->getWriterIndex() );
// Do the update as soon as there is no transaction
if ( $dbw && $dbw->trxLevel() ) {
$waitingOnTrx = true;
$dbw->onTransactionIdle( function() use ( &$waitingOnTrx ) {
DeferredUpdates::doUpdates();
$waitingOnTrx = false;
} );
} else {
self::doUpdates();
}
}
}
/**
* 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
*/
public static function addCallableUpdate( $callable ) {
self::addUpdate( new MWCallableUpdate( $callable ) );
}
/**
* Do any deferred updates and clear the list
*
* @param string $commit Set to 'commit' to commit after every update to
* prevent lock contention
*/
public static function doUpdates( $commit = '' ) {
$updates = self::$updates;
while ( count( $updates ) ) {
self::clearPendingUpdates();
/** @var DeferrableUpdate $update */
foreach ( $updates as $update ) {
try {
$update->doUpdate();
if ( $commit === 'commit' ) {
wfGetLBFactory()->commitMasterChanges();
}
} catch ( Exception $e ) {
// We don't want exceptions thrown during deferred updates to
// be reported to the user since the output is already sent.
// Instead we just log them.
if ( !$e instanceof ErrorPageError ) {
MWExceptionHandler::logException( $e );
}
}
}
$updates = self::$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::$updates = array();
}
}
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