PoolCounterWork.php

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<?php
abstract class PoolCounterWork {
    protected $type = 'generic';
    protected $cacheable = false; // does this override getCachedWork() ?
    private $poolCounter;

    public function __construct( $type, $key ) {
        $this->type = $type;
        $this->poolCounter = PoolCounter::factory( $type, $key );
    }

    abstract public function doWork();

    public function getCachedWork() {
        return false;
    }

    public function fallback() {
        return false;
    }

    public function error( $status ) {
        return false;
    }

    public function logError( $status ) {
        $key = $this->poolCounter->getKey();

        wfDebugLog( 'poolcounter', "Pool key '$key' ({$this->type}): "
            . $status->getMessage()->inLanguage( 'en' )->useDatabase( false )->text() );
    }

    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( $errors[$status->value] ?? 'pool-errorunknown' );
                $this->logError( $status );
                return $this->error( $status );
        }
    }
}