<?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
+ * 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,
+ *
+ * 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'.
+ * 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
+ * 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 LOCKED = 1; /* Lock acquired */
const RELEASED = 2; /* Lock released */
- const DONE = 3; /* Another one 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 */
+ 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 */
/**
* I want to do this task and I need to do it myself.
- *
+ *
* @return Locked/Error
*/
abstract function acquireForMe();
/**
- * I want to do this task, but if anyone else does it
+ * 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 Locked/Done/Error
*/
abstract function acquireForAnyone();
/**
* I have successfully finished my task.
- * Lets another one grab the lock, and returns the workers
+ * Lets another one grab the lock, and returns the workers
* waiting on acquireForAnyone()
- *
+ *
* @return Released/NotLocked/Error
*/
abstract function release();
-
+
/**
* $key: All workers with the same key share the lock.
- * $workers: It wouldn't be a good idea to have more than this number of
+ * $workers: It wouldn't be a good idea to have more than this number of
* workers doing the task simultaneously.
- * $maxqueue: If this number of workers are already working/waiting,
+ * $maxqueue: If this number of workers are already working/waiting,
* fail instead of wait.
* $timeout: Maximum time in seconds to wait for the lock.
*/
protected $key, $workers, $maxqueue, $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;
}
$conf = $wgPoolCounterConf[$type];
$class = $conf['class'];
-
+
return new $class( $conf, $type, $key );
}
-
+
protected function __construct( $conf, $type, $key ) {
$this->key = $key;
$this->workers = $conf['workers'];
}
class PoolCounter_Stub extends PoolCounter {
+
+ /**
+ * @return Status
+ */
function acquireForMe() {
return Status::newGood( PoolCounter::LOCKED );
}
+ /**
+ * @return Status
+ */
function acquireForAnyone() {
return Status::newGood( PoolCounter::LOCKED );
}
+ /**
+ * @return Status
+ */
function release() {
return Status::newGood( PoolCounter::RELEASED );
}
-
+
public function __construct() {
/* No parameters needed */
}
*/
abstract class PoolCounterWork {
protected $cacheable = false; //Does this override getCachedWork() ?
-
+
/**
* Actually perform the work, caching it if needed.
*/
}
/**
- * A work not so good (eg. expired one) but better than an error
+ * A work not so good (eg. expired one) but better than an error
* message.
* @return mixed work result or false
*/
function fallback() {
return false;
}
-
+
/**
* Do something with the error, like showing it to the user.
+ * @return bool
*/
- function error( $status ) {
+ function error( $status ) {
return false;
}
-
+
+ /**
+ * Log an error
+ *
+ * @param $status Status
+ */
+ function logError( $status ) {
+ wfDebugLog( 'poolcounter', $status->getWikiText() );
+ }
+
/**
* Get the result of the work (whatever it is), or false.
+ * @param $skipcache bool
+ * @return bool|mixed
*/
function execute( $skipcache = false ) {
if ( $this->cacheable && !$skipcache ) {
} else {
$status = $this->poolCounter->acquireForMe();
}
-
- $result = false;
-
- if ( $status->isOK() ) {
- 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 $this->execute( true );
- }
+
+ if ( !$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;
-
- 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' );
- /* continue to the error */
- }
+ }
+ /* 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 );
}
- return $this->error( $status );
}
-
+
function __construct( $type, $key ) {
$this->poolCounter = PoolCounter::factory( $type, $key );
}
dépôts / lhc / web / wiklou.git / blobdiff