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Diffstat (limited to 'includes/poolcounter/PoolCounterWork.php')
| -rw-r--r-- | includes/poolcounter/PoolCounterWork.php | 160 |
1 files changed, 160 insertions, 0 deletions
diff --git a/includes/poolcounter/PoolCounterWork.php b/includes/poolcounter/PoolCounterWork.php new file mode 100644 index 00000000..c0be7a1b --- /dev/null +++ b/includes/poolcounter/PoolCounterWork.php @@ -0,0 +1,160 @@ +<?php +/** + * Provides of semaphore semantics for restricting the number + * of workers that may be concurrently performing the same task. + * + * 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 + */ + +/** + * Class for dealing with PoolCounters using class members + */ +abstract class PoolCounterWork { + /** @var string */ + protected $type = 'generic'; + /** @var bool */ + protected $cacheable = false; // does this override getCachedWork() ? + + /** + * @param string $type The type of PoolCounter to use + * @param string $key Key that identifies the queue this work is placed on + */ + public function __construct( $type, $key ) { + $this->type = $type; + $this->poolCounter = PoolCounter::factory( $type, $key ); + } + + /** + * Actually perform the work, caching it if needed + * @return mixed Work result or false + */ + abstract public function doWork(); + + /** + * Retrieve the work from cache + * @return mixed Work result or false + */ + public function getCachedWork() { + return false; + } + + /** + * A work not so good (eg. expired one) but better than an error + * message. + * @return mixed Work result or false + */ + public function fallback() { + return false; + } + + /** + * Do something with the error, like showing it to the user. + * + * @param Status $status + * + * @return bool + */ + public function error( $status ) { + return false; + } + + /** + * Log an error + * + * @param Status $status + * @return void + */ + public function logError( $status ) { + $key = $this->poolCounter->getKey(); + + wfDebugLog( 'poolcounter', "Pool key '$key' ({$this->type}): " + . $status->getMessage()->inLanguage( 'en' )->useDatabase( false )->text() ); + } + + /** + * Get the result of the work (whatever it is), or the result of the error() function. + * This returns the result of the first applicable method that returns a non-false value, + * where the methods are checked in the following order: + * - a) doWork() : Applies if the work is exclusive or no another process + * is doing it, and on the condition that either this process + * successfully entered the pool or the pool counter is down. + * - b) doCachedWork() : Applies if the work is cacheable and this blocked on another + * process which finished the work. + * - c) fallback() : Applies for all remaining cases. + * If these all fall through (by returning false), then the result of error() is returned. + * + * @param bool $skipcache + * @return mixed + */ + public function execute( $skipcache = false ) { + if ( $this->cacheable && !$skipcache ) { + $status = $this->poolCounter->acquireForAnyone(); + } else { + $status = $this->poolCounter->acquireForMe(); + } + + if ( !$status->isOK() ) { + // Respond gracefully to complete server breakage: just log it and do the work + $this->logError( $status ); + return $this->doWork(); + } + + switch ( $status->value ) { + case PoolCounter::LOCK_HELD: + // Better to ignore nesting pool counter limits than to fail. + // Assume that the outer pool limiting is reasonable enough. + /* no break */ + case PoolCounter::LOCKED: + $result = $this->doWork(); + $this->poolCounter->release(); + return $result; + + case PoolCounter::DONE: + $result = $this->getCachedWork(); + if ( $result === false ) { + /* That someone else work didn't serve us. + * Acquire the lock for me + */ + return $this->execute( true ); + } + return $result; + + case PoolCounter::QUEUE_FULL: + case PoolCounter::TIMEOUT: + $result = $this->fallback(); + + if ( $result !== false ) { + return $result; + } + /* no break */ + + /* These two cases should never be hit... */ + case PoolCounter::ERROR: + default: + $errors = array( + PoolCounter::QUEUE_FULL => 'pool-queuefull', + PoolCounter::TIMEOUT => 'pool-timeout' ); + + $status = Status::newFatal( isset( $errors[$status->value] ) + ? $errors[$status->value] + : 'pool-errorunknown' ); + $this->logError( $status ); + return $this->error( $status ); + } + } +} |