1 files changed, 160 insertions, 0 deletions
diff --git a/www/wiki/includes/poolcounter/PoolCounterWork.php b/www/wiki/includes/poolcounter/PoolCounterWork.php
new file mode 100644
index 00000000..a570d78c
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+++ b/www/wiki/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 class of actions to limit concurrency for (task type)
+	 * @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 = [
+					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 );
+		}
+	}
+}