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Diffstat (limited to 'includes/PoolCounter.php')
| -rw-r--r-- | includes/PoolCounter.php | 329 |
1 files changed, 0 insertions, 329 deletions
diff --git a/includes/PoolCounter.php b/includes/PoolCounter.php deleted file mode 100644 index 2dac9388..00000000 --- a/includes/PoolCounter.php +++ /dev/null @@ -1,329 +0,0 @@ -<?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 - */ - -/** - * When you have many workers (threads/servers) giving service, and a - * cached item expensive to produce expires, you may get several workers - * doing the job at the same time. - * - * Given enough requests and the item expiring fast (non-cacheable, - * lots of edits...) that single work can end up unfairly using most (all) - * of the cpu of the pool. This is also known as 'Michael Jackson effect' - * since this effect triggered on the english wikipedia on the day Michael - * Jackson died, the biographical article got hit with several edits per - * minutes and hundreds of read hits. - * - * The PoolCounter provides semaphore semantics for restricting the number - * of workers that may be concurrently performing such single task. - * - * By default PoolCounter_Stub is used, which provides no locking. You - * can get a useful one in the PoolCounter extension. - */ -abstract class PoolCounter { - /* Return codes */ - const LOCKED = 1; /* Lock acquired */ - const RELEASED = 2; /* Lock released */ - const DONE = 3; /* Another worker did the work for you */ - - const ERROR = -1; /* Indeterminate error */ - const NOT_LOCKED = -2; /* Called release() with no lock held */ - const QUEUE_FULL = -3; /* There are already maxqueue workers on this lock */ - const TIMEOUT = -4; /* Timeout exceeded */ - const LOCK_HELD = -5; /* Cannot acquire another lock while you have one lock held */ - - /** @var string All workers with the same key share the lock */ - protected $key; - /** @var integer Maximum number of workers doing the task simultaneously */ - protected $workers; - /** @var integer If this number of workers are already working/waiting, fail instead of wait */ - protected $maxqueue; - /** @var float Maximum time in seconds to wait for the lock */ - protected $timeout; - - /** - * @param array $conf - * @param string $type - * @param string $key - */ - protected function __construct( $conf, $type, $key ) { - $this->key = $key; - $this->workers = $conf['workers']; - $this->maxqueue = $conf['maxqueue']; - $this->timeout = $conf['timeout']; - } - - /** - * Create a Pool counter. This should only be called from the PoolWorks. - * - * @param $type - * @param $key - * - * @return PoolCounter - */ - public static function factory( $type, $key ) { - global $wgPoolCounterConf; - if ( !isset( $wgPoolCounterConf[$type] ) ) { - return new PoolCounter_Stub; - } - $conf = $wgPoolCounterConf[$type]; - $class = $conf['class']; - - return new $class( $conf, $type, $key ); - } - - /** - * I want to do this task and I need to do it myself. - * - * @return Status Value is one of Locked/Error - */ - abstract public function acquireForMe(); - - /** - * I want to do this task, but if anyone else does it - * instead, it's also fine for me. I will read its cached data. - * - * @return Status Value is one of Locked/Done/Error - */ - abstract public function acquireForAnyone(); - - /** - * I have successfully finished my task. - * Lets another one grab the lock, and returns the workers - * waiting on acquireForAnyone() - * - * @return Status value is one of Released/NotLocked/Error - */ - abstract public function release(); -} - -class PoolCounter_Stub extends PoolCounter { - public function __construct() { - /* No parameters needed */ - } - - public function acquireForMe() { - return Status::newGood( PoolCounter::LOCKED ); - } - - public function acquireForAnyone() { - return Status::newGood( PoolCounter::LOCKED ); - } - - public function release() { - return Status::newGood( PoolCounter::RELEASED ); - } -} - -/** - * Class for dealing with PoolCounters using class members - */ -abstract class PoolCounterWork { - 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->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. - * @return bool - */ - function error( $status ) { - return false; - } - - /** - * Log an error - * - * @param $status Status - * @return void - */ - function logError( $status ) { - wfDebugLog( 'poolcounter', $status->getWikiText() ); - } - - /** - * 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 $skipcache bool - * @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::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 ); - } - } -} - -/** - * Convenience class for dealing with PoolCounters using callbacks - * @since 1.22 - */ -class PoolCounterWorkViaCallback extends PoolCounterWork { - /** @var callable */ - protected $doWork; - /** @var callable|null */ - protected $doCachedWork; - /** @var callable|null */ - protected $fallback; - /** @var callable|null */ - protected $error; - - /** - * Build a PoolCounterWork class from a type, key, and callback map. - * - * The callback map must at least have a callback for the 'doWork' method. - * Additionally, callbacks can be provided for the 'doCachedWork', 'fallback', - * and 'error' methods. Methods without callbacks will be no-ops that return false. - * If a 'doCachedWork' callback is provided, then execute() may wait for any prior - * process in the pool to finish and reuse its cached result. - * - * @param string $type - * @param string $key - * @param array $callbacks Map of callbacks - * @throws MWException - */ - public function __construct( $type, $key, array $callbacks ) { - parent::__construct( $type, $key ); - foreach ( array( 'doWork', 'doCachedWork', 'fallback', 'error' ) as $name ) { - if ( isset( $callbacks[$name] ) ) { - if ( !is_callable( $callbacks[$name] ) ) { - throw new MWException( "Invalid callback provided for '$name' function." ); - } - $this->$name = $callbacks[$name]; - } - } - if ( !isset( $this->doWork ) ) { - throw new MWException( "No callback provided for 'doWork' function." ); - } - $this->cacheable = isset( $this->doCachedWork ); - } - - public function doWork() { - return call_user_func_array( $this->doWork, array() ); - } - - public function getCachedWork() { - if ( $this->doCachedWork ) { - return call_user_func_array( $this->doCachedWork, array() ); - } - return false; - } - - function fallback() { - if ( $this->fallback ) { - return call_user_func_array( $this->fallback, array() ); - } - return false; - } - - function error( $status ) { - if ( $this->error ) { - return call_user_func_array( $this->error, array( $status ) ); - } - return false; - } -} |