X-Git-Url: http://git.heureux-cyclage.org/?a=blobdiff_plain;f=includes%2FPoolCounter.php;h=452dbc547f73a2e8a166ee6af1e424e0e4e3ffc6;hb=a5028bfe5f638e53ab002114435e8e480ef4bbc9;hp=c24993e8350aa776b3fc6b555bd9b7b0c25237b0;hpb=3342af373caa4545c237b3870ca383d2fdf0e0c9;p=lhc%2Fweb%2Fwiklou.git

diff --git a/includes/PoolCounter.php b/includes/PoolCounter.php
index c24993e835..452dbc547f 100644
--- a/includes/PoolCounter.php
+++ b/includes/PoolCounter.php
@@ -1,67 +1,98 @@
 <?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;
@@ -70,10 +101,10 @@ abstract class PoolCounter {
 		}
 		$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'];
@@ -83,18 +114,28 @@ abstract class PoolCounter {
 }
 
 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 */
 	}
@@ -105,7 +146,7 @@ class PoolCounter_Stub extends PoolCounter {
  */
 abstract class PoolCounterWork {
 	protected $cacheable = false; //Does this override getCachedWork() ?
-	
+
 	/**
 	 * Actually perform the work, caching it if needed.
 	 */
@@ -120,30 +161,35 @@ abstract class PoolCounterWork {
 	}
 
 	/**
-	 * 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 ) {
@@ -151,46 +197,49 @@ abstract class PoolCounterWork {
 		} else {
 			$status = $this->poolCounter->acquireForMe();
 		}
-		
-		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 );
 		}
-		$this->logError( $status );
-		return $this->error( $status );
 	}
-	
+
 	function __construct( $type, $key ) {
 		$this->poolCounter = PoolCounter::factory( $type, $key );
 	}