<?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'.
- * The PoolCounter provides semaphore semantics for restricting the number
+ * 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 */
- /**
- * I want to do this task and I need to do it myself.
- *
- * @return Locked/Error
- */
- abstract function acquireForMe();
+ 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, 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();
+ /** @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;
/**
- * I have successfully finished my task.
- * 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 doing the task simultaneously.
- * $maxqueue: If this number of workers are already working/waiting,
- * fail instead of wait.
- * $timeout: Maximum time in seconds to wait for the lock.
+ * @param array $conf
+ * @param string $type
+ * @param string $key
*/
- protected $key, $workers, $maxqueue, $timeout;
-
+ 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;
}
$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'];
- $this->maxqueue = $conf['maxqueue'];
- $this->timeout = $conf['timeout'];
- }
+
+ /**
+ * 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 {
- function acquireForMe() {
- return PoolCounter::LOCKED;
+ public function __construct() {
+ /* No parameters needed */
}
- function acquireForAnyone() {
- return PoolCounter::LOCKED;
+ public function acquireForMe() {
+ return Status::newGood( PoolCounter::LOCKED );
}
- function release() {
- return PoolCounter::RELEASED;
+ public function acquireForAnyone() {
+ return Status::newGood( PoolCounter::LOCKED );
}
-
- public function __construct() {
- /* No parameters needed */
+
+ public function release() {
+ return Status::newGood( PoolCounter::RELEASED );
}
}
/**
- * Handy class for dealing with PoolCounters using class members instead of callbacks.
+ * Class for dealing with PoolCounters using class members
*/
abstract class PoolCounterWork {
protected $cacheable = false; //Does this override getCachedWork() ?
-
+
/**
- * Actually perform the work, caching it if needed.
+ * @param string $type The type of PoolCounter to use
+ * @param string $key Key that identifies the queue this work is placed on
*/
- abstract function doWork();
+ 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
*/
- function getCachedWork() {
+ public function getCachedWork() {
return false;
}
/**
- * 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() {
+ public 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
+ * @return void
+ */
+ 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 ) {
+ public function execute( $skipcache = false ) {
if ( $this->cacheable && !$skipcache ) {
$status = $this->poolCounter->acquireForAnyone();
} else {
$status = $this->poolCounter->acquireForMe();
}
-
- $result = false;
- switch ( is_int( $status ) ? $status : PoolCounter::ERROR ) {
+
+ if ( !$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 ) {
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 );
}
}
-
- function __construct( $type, $key ) {
- $this->poolCounter = PoolCounter::factory( $type, $key );
+}
+
+/**
+ * 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;
}
}
dépôts / lhc / web / wiklou.git / blobdiff