Tourstream\RedisLockStrategy\RedisLockStrategy

Complexity

Total Complexity

24

Size/Duplication

Total Lines	177
Duplicated Lines	0 %

Coupling/Cohesion

Components	1
Dependencies	3

Test Coverage

Coverage

75.44%

Importance

Changes	3
Bugs	1	Features	0

8 Methods

Rating	Name	Duplication	Size	Complexity
D	__construct()	0	43	9
A	getCapabilities()	0	4	1
A	getPriority()	0	4	1
A	isAcquired()	0	4	1
A	destroy()	0	4	1
A	release()	0	10	2
A	create()	0	12	3
B	acquire()	0	32	6

<?php

namespace Tourstream\RedisLockStrategy;

/***************************************************************
 *  Copyright notice
 *
 *  (c) 2017 Alexander Miehe (alexander.miehe@tourstream.eu)
 *  All rights reserved
 *
 *  You may not remove or change the name of the author above. See:
 *  http://www.gnu.org/licenses/gpl-faq.html#IWantCredit
 *
 *  This script is part of the Typo3 project. The Typo3 project 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 3 of the License, or
 *  (at your option) any later version.
 *
 *  The GNU General Public License can be found at
 *  http://www.gnu.org/copyleft/gpl.html.
 *  A copy is found in the LICENSE and distributed with these scripts.
 *
 *
 *  This script 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.
 *
 *  This copyright notice MUST APPEAR in all copies of the script!
 ***************************************************************/

use TYPO3\CMS\Core\Locking\Exception\LockAcquireException;
use TYPO3\CMS\Core\Locking\Exception\LockCreateException;
use TYPO3\CMS\Core\Locking\Exception\LockAcquireWouldBlockException;
use TYPO3\CMS\Core\Locking\LockingStrategyInterface;

/**
 * @author Alexander Miehe <alexander.miehe@tourstream.eu>
 */
class RedisLockStrategy implements LockingStrategyInterface
{
    /**
     * @var \Redis A key-value data store
     */
    private $redis;

    /**
     * @var string The locking subject, i.e. a string to discriminate the lock
     */
    private $subject;

    /**
     * @var boolean TRUE if lock is acquired
     */
    private $isAcquired = false;

    /**
     * @var int Seconds the lock remains persistent
     */
    private $ttl = 3600;

    /**
     * @var int Seconds to wait for a lock
     */
    private $blTo = 60;

    /**
     * @inheritdoc
     */
    public function __construct($subject)
    {
        $config = null;

        if (\array_key_exists('redis_lock', $GLOBALS['TYPO3_CONF_VARS']['SYS'])) {
            $config = $GLOBALS['TYPO3_CONF_VARS']['SYS']['redis_lock'];
        }

        if (!\is_array($config)) {
            throw new LockCreateException('no configuration for redis lock strategy found');
        }

        if (!\array_key_exists('host', $config)) {
            throw new LockCreateException('no host for redis lock strategy found');
        }
        $port = 6379;

        if (\array_key_exists('port', $config)) {
            $port = (int) $config['port'];
        }

        if (!\array_key_exists('database', $config)) {
            throw new LockCreateException('no database for redis lock strategy found');
        }

        if (\array_key_exists('ttl', $config)) {
            $this->ttl = (int) $config['ttl'];
        }

        $this->subject = $subject;
        $this->redis   = new \Redis();
        $this->redis->connect($config['host'], $port);

        if (\array_key_exists('auth', $config)) {
            $this->redis->auth($config['auth']);
        }

        $this->redis->select((int) $config['database']);

        if (!$this->redis->exists($this->subject)) {
            $this->create();
        }
    }

    /**
     * @inheritdoc
     */
    public static function getCapabilities()
    {
        return self::LOCK_CAPABILITY_EXCLUSIVE | self::LOCK_CAPABILITY_NOBLOCK;
    }

    /**
     * @inheritdoc
     */
    public static function getPriority()
    {
        return 100;
    }

    /**
     * @inheritdoc
     */
    public function acquire($mode = self::LOCK_CAPABILITY_EXCLUSIVE)
    {
        if ($this->isAcquired) {
            return true;
        }

        if ($mode & self::LOCK_CAPABILITY_EXCLUSIVE) {

            if ($mode & self::LOCK_CAPABILITY_NOBLOCK) {

                // this does not block
                $this->isAcquired = (bool) $this->redis->lPop($this->subject);

                if (!$this->isAcquired) {
                    throw new LockAcquireWouldBlockException('could not acquire lock');
                }
            } else {

                // this blocks iff the list is empty
                $this->isAcquired = (bool) $this->redis->blPop([$this->subject], $this->blTo);

                if (!$this->isAcquired) {
                    throw new LockAcquireException('could not acquire lock');
                }
            }

        } else {
            throw new LockAcquireException('insufficient capabilities');
        }

        return true;
    }

    /**
     * @inheritdoc
     */
    public function isAcquired()
    {
        return $this->isAcquired;
    }

    /**
     * @inheritdoc
     */
    public function destroy()
    {
        $this->redis->del($this->subject);
    }

    /**
     * @inheritdoc
     */
    public function release()
    {
        if (!$this->isAcquired) {
            return true;
        }

        $this->isAcquired = !$this->create();

        return !$this->isAcquired;
    }

    /**
     * create synchronization object, i.e.
     * a simple list with some single random value
     *
     * @return boolean TRUE on success
     * @throws LockCreateException
     */
    private function create()
    {
        if (!$this->redis->rPush($this->subject, uniqid())) {
            throw new LockCreateException('could not create lock entry');
        }

        if (!$this->redis->expire($this->subject, $this->ttl)) {
            throw new LockCreateException('could not set ttl to lock entry');
        }

        return true;
    }

}