yfix/yf

<?php

/**
 * Relock algorithm http://antirez.com/news/77
 * Forked from https://github.com/ronnylt/redlock-php.
 */
class yf_wrapper_redlock
{
    private $retry_delay;
    private $retry_count;
    private $clock_drift_factor = 0.01;
    private $quorum;
    private $servers = [];
    private $instances = [];


    public function setup(array $params = [])
    {
        $this->servers = $params['servers'] ?: [[
            $this->_get_conf('REDIS_HOST', '127.0.0.1', $params),
            $this->_get_conf('REDIS_PORT', 6379, $params),
            $timeout = 0.01,
        ]];
        $this->quorum = min(count((array) $this->servers), (count((array) $this->servers) / 2 + 1));
        if ($params['instances']) {
            $this->instances = $params['instances'];
            $this->quorum = min(count((array) $this->instances), (count((array) $this->instances) / 2 + 1));
        }
        $this->retry_delay = $params['retry_delay'] ?: 200;
        $this->retry_count = $params['retry_count'] ?: 3;
    }


    public function _init()
    {
        $this->setup();
        if ( ! $this->instances) {
            $redis = redis();
            $redis->connect();
            $this->instances[] = $redis;
        }
    }

    /**
     * @param mixed $resource
     * @param mixed $ttl
     */
    public function lock($resource, $ttl)
    {
        $this->init_instances();

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

        do {
            $n = 0;

            $start_time = microtime(true) * 1000;

            foreach ((array) $this->instances as $instance) {
                if ($this->lock_instance($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->clock_drift_factor) + 2;

            $validity_time = $ttl - (microtime(true) * 1000 - $start_time) - $drift;

            if ($n >= $this->quorum && $validity_time > 0) {
                return [
                    'validity' => $validity_time,
                    'resource' => $resource,
                    'token' => $token,
                ];
            }
            foreach ((array) $this->instances as $instance) {
                $this->unlock_instance($instance, $resource, $token);
            }


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

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

        return false;
    }


    public function unlock(array $lock)
    {
        $this->init_instances();
        $resource = $lock['resource'];
        $token = $lock['token'];
        foreach ((array) $this->instances as $instance) {
            $this->unlock_instance($instance, $resource, $token);
        }
    }


    private function init_instances()
    {
        if (empty($this->instances)) {
            foreach ((array) $this->servers as $server) {
                list($host, $port, $timeout) = $server;
                $redis = redis()->factory(['host' => $host, 'port' => $port, 'timeout' => $timeout]);
                $this->instances[] = $redis;
            }
        }
    }

    /**
     * @param mixed $instance
     * @param mixed $resource
     * @param mixed $token
     * @param mixed $ttl
     */
    private function lock_instance($instance, $resource, $token, $ttl)
    {
        return $instance->set($resource, $token, ['NX', 'PX' => $ttl]);
    }

    /**
     * @param mixed $instance
     * @param mixed $resource
     * @param mixed $token
     */
    private function unlock_instance($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, [$resource, $token], 1);
    }

    /**
     * @param mixed $name
     * @param null|mixed $default
     */
    private function _get_conf($name, $default = null, array $params = [])
    {
        if (isset($params[$name])) {
            return $params[$name];
        }
        $from_env = getenv($name);
        if ($from_env !== false) {
            return $from_env;
        }
        global $CONF;
        if (isset($CONF[$name])) {
            $from_conf = $CONF[$name];
            return $from_conf;
        }
        if (defined($name) && ($val = constant($name)) != $name) {
            return $val;
        }
        return $default;
    }
}