Redis 锁的使用

<?php

/**
 * Redis distributed locks in PHP
 * @author assasin <>
 */
class RedisLock {

    private $retryDelay;
    private $retryCount;
    private $clockDriftFactor = 0.01;
    private $quorum;
    private $servers = array();
    private $instances = array();

    /**
     * Redis default prefix
     * @var string
     */
    public $prefix = "";

    /**
     * The database to use, defaults to 1
     * @var integer
     */
    public $database = 1;

    public function __construct(array $servers = array(array('127.0.0.1', 6379, 0.01)), $retryDelay = 200, $retryCount = 3) {
        $this->servers = $servers;

        $this->retryDelay = $retryDelay;
        $this->retryCount = $retryCount;

        $this->quorum = min(count($servers), (count($servers) / 2 + 1));
    }

    public function lock($resource, $ttl) {
        $this->initInstances();

        $token = uniqid();
        $retry = $this->retryCount;

        do {
            $n = 0;

            $startTime = microtime(true) * 1000;

            foreach ($this->instances as $instance) {
                if ($this->lockInstance($instance, $resource, $token, $ttl)) {
                    $n++;
                }
            }

            # Add 2 milliseconds to the drift to account for Redis expires
            # precision, which is 1 millisecond, plus 1 millisecond min drift
            # for small TTLs.
            $drift = ($ttl * $this->clockDriftFactor) + 2;

            $validityTime = $ttl - (microtime(true) * 1000 - $startTime) - $drift;

            if ($n >= $this->quorum && $validityTime > 0) {
                return array(
                    'validity' => $validityTime,
                    'resource' => $resource,
                    'token' => $token,
                );
            } else {
                foreach ($this->instances as $instance) {
                    $this->unlockInstance($instance, $resource, $token);
                }
            }

            // Wait a random delay before to retry
            $delay = mt_rand(floor($this->retryDelay / 2), $this->retryDelay);
            usleep($delay * 1000);

            $retry--;
        } while ($retry > 0);

        return false;
    }

    public function unlock(array $lock) {
        $this->initInstances();
        $resource = $lock['resource'];
        $token = $lock['token'];

        foreach ($this->instances as $instance) {
            $this->unlockInstance($instance, $resource, $token);
        }
    }

    private function initInstances() {
        if (empty($this->instances)) {
            foreach ($this->servers as $server) {
                list($host, $port, $timeout) = $server;
                $redis = new \Redis();
                if ($redis->connect($host, $port, $timeout) === false) {
                    continue;
                }
                $redis->setOption(Redis::OPT_PREFIX, $this->prefix);
                $redis->select($this->database);

                $this->instances[] = $redis;
            }
        }
    }

    private function lockInstance($instance, $resource, $token, $ttl) {
        return $instance->set($resource, $token, array('NX', 'PX' => $ttl));
    }

    private function unlockInstance($instance, $resource, $token) {
        $script = '
            if redis.call("GET", KEYS[1]) == ARGV[1] then
                return redis.call("DEL", KEYS[1])
            else
                return 0
            end
        ';
        return $instance->eval（$script, array($resource, $token), 1);
    }

}