PoolCounter.php

Go to the documentation of this file.

<?php
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 */

    protected $key;
    protected $workers;
    protected $slots = 0;
    protected $maxqueue;
    protected $timeout;

    private $isMightWaitKey;
    private static $acquiredMightWaitKey = 0;

    protected function __construct( $conf, $type, $key ) {
        $this->workers = $conf['workers'];
        $this->maxqueue = $conf['maxqueue'];
        $this->timeout = $conf['timeout'];
        if ( isset( $conf['slots'] ) ) {
            $this->slots = $conf['slots'];
        }

        if ( $this->slots ) {
            $key = $this->hashKeyIntoSlots( $key, $this->slots );
        }
        $this->key = $key;
        $this->isMightWaitKey = !preg_match( '/^nowait:/', $this->key );
    }

    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 );
    }

    public function getKey() {
        return $this->key;
    }

    abstract public function acquireForMe();

    abstract public function acquireForAnyone();

    abstract public function release();

    final protected function precheckAcquire() {
        if ( $this->isMightWaitKey ) {
            if ( self::$acquiredMightWaitKey ) {
                /*
                 * The poolcounter itself is quite happy to allow you to wait
                 * on another lock while you have a lock you waited on already
                 * but we think that it is unlikely to be a good idea.  So we
                 * made it an error.  If you are _really_ _really_ sure it is a
                 * good idea then feel free to implement an unsafe flag or
                 * something.
                 */
                return Status::newFatal( 'poolcounter-usage-error',
                    'You may only aquire a single non-nowait lock.' );
            }
        } elseif ( $this->timeout !== 0 ) {
            return Status::newFatal( 'poolcounter-usage-error',
                'Locks starting in nowait: must have 0 timeout.' );
        }
        return Status::newGood();
    }

    final protected function onAcquire() {
        self::$acquiredMightWaitKey |= $this->isMightWaitKey;
    }

    final protected function onRelease() {
        self::$acquiredMightWaitKey &= !$this->isMightWaitKey;
    }

    protected function hashKeyIntoSlots( $key, $slots ) {
        return hexdec( substr( sha1( $key ), 0, 4 ) ) % $slots;
    }
}

// @codingStandardsIgnoreStart Squiz.Classes.ValidClassName.NotCamelCaps
class PoolCounter_Stub extends PoolCounter {
    // @codingStandardsIgnoreEnd

    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 );
    }
}