Gearman with multiple servers and php workers

Question

I\'m having a problem with gearman workers running on multiple servers which i can\'t seem to solve.

The problem occurs when a worker server is taken offline, rather tha

Answer 1

since 'addServer' from gearman client is not working properly this code can choose a jobserver randomly and if fails try the next one, this way you can balance the load.

        // job servers
        $jobservers = array('192.168.1.1','192.168.1.2');
        // prepare gearman client
        $gmclient = new GearmanClient();
        // shuffle job servers (deliver jobs equally by server)
        shuffle($jobservers);
        // add job servers
        foreach($jobservers as $jobserver) {
            // add random jobserver
            $gmclient->addServer($jobserver);
            // check server state if ok end foreach
            if (@$gmclient->ping('ping')) break;
            // if connections fails reset client
            $gmclient = new GearmanClient();
        }

Answer 2

I use this class, which keep track of which jobs work on which servers. It hasn't been thoroughly tested, just wrote it now. I've pasted an edited version, so there might be a typo or somesuch, but otherwise appears to solve the issue.

<?
class MyGearmanClient {
        static $server = "server1,server2,server3";
        static $server_array = false;
        static $workingServers = false;
        static $gmclient = false;
        static $timeout = 5000;
        static $defaultTimeout = 5000;

        static function randomServer() {
                return self::$server_array[rand(0, count(self::$server_array) -1)];
        }

        static function getServer($job = false) {
                if (self::$server_array == false) {
                        self::$server_array = explode(",", self::$server);
                        self::$workingServers = array();
                }

                $serverList = array();
                if ($job) {
                        if (array_key_exists($job, self::$workingServers)) {
                                foreach (self::$server_array as $server) {
                                        if (array_key_exists($server, self::$workingServers[$job])) {
                                                if (self::$workingServers[$job][$server]) {
                                                        $serverList[] = $server;
                                                }
                                        } else {
                                                $serverList[] = $server;
                                        }
                                }
                                if (count($serverList) == 0) {
                                        # All servers have failed, need to insert all the servers again and retry.
                                        $serverList = self::$workingServers[$job] = self::$server_array;
                                }
                                return $serverList[rand(0, count($serverList) - 1)];
                        } else {
                                return self::randomServer();
                        }
                } else {
                        return self::randomServer();
                }
        }

        static function serverWorked($server, $job) {
                self::$workingServers[$job][$server] = $server;
        }

        static function serverFailed($server, $job) {
                self::$workingServers[$job][$server] = false;
        }

        static function Connect($server = false, $job = false) {
                if ($server) {
                        self::$server = self::getServer();
                }

                self::$gmclient= new GearmanClient();
                self::$gmclient->setTimeout(self::$timeout);

                # add the default job server
                self::$gmclient->addServer($server = self::getServer($job));

                return $server;
        }

        static function Destroy() {
                self::$gmclient = false;
        }

        static function Client($name, $vars, $timeout = false) {
                if (is_int($timeout)) {
                        self::$timeout = $timeout;
                } else {
                        self::$timeout = self::$defaultTimeout;
                }


                do {
                        $server = self::Connect(false, $name);
                        $value = self::$gmclient->do($name, $vars);
                        $return_code = self::$gmclient->returnCode();
                        if (!$value) {
                                $error_message = self::$gmclient->error();
                                if ($return_code == 47) {
                                        self::serverFailed($server, $name);
                                        if (count(self::$server_array) > 1) {
                                             // ADDED SINGLE SERVER LOOP AVOIDANCE // echo "Timeout on server $server, trying another server...\n";
                                             continue;
                                        } else {
                                             return false;
                                        }
                                }
                                echo "ERR: $error_message ($return_code)\n";
                        }
                        # printf("Worker has returned\n");
                        $short_value = substr($value, 0, 80);
                        switch ($return_code)
                        {
                        case GEARMAN_WORK_DATA:
                                echo "DATA: $short_value\n";
                                break;
                        case GEARMAN_SUCCESS:
                                self::serverWorked($server, $name);
                                break;
                        case GEARMAN_WORK_STATUS:
                                list($numerator, $denominator)= self::$gmclient->doStatus();
                                echo "Status: $numerator/$denominator\n";
                                break;
                        case GEARMAN_TIMEOUT:
                                // self::Connect();
                                // Fall through
                        default:
                                echo "ERR: $error_message " . self::$gmclient->error() . " ($return_code)\n";
                                break;
                        }
                }
                while($return_code != GEARMAN_SUCCESS);

                $rv = unserialize($value);
                return $rv["rv"];
        }
}

# Example usage:
#    $rv = MyGearmanClient::Client("Function", $args);

?>

Answer 3

Solution tested and working ok.

     $client = new GearmanClient();
     if(!$client->addServer("11.11.65.73",4730))
        $client->addServer("11.11.65.79",4730);

Answer 4

Our tests with multiple gearman servers shows that if the last server in the list (192.168.1.201 in your case) is taken down, the workers stop executing the way you are describing. (Also, the workers grab jobs from the last server. They process jobs on .200 only if on .201 there are no jobs).

It seems that this is a bug with the linked list in the gearman server, which is reported to be fixed multiple times, but with all available versions of gearman, the bug persist. Sorry, I know that's not a solution, but we had the same problem and didn't found a solution. (if someone can provide working solution for this problem, I agree to give large bounty)

Answer 5

Further to @Darhazer 's comment above. We found that as well and solved like thus :-

// Gearman workers show a strong preference for servers at the end of a list so randomize the order
$worker = new GearmanWorker();
$s2 = explode(",", Configure::read('workers.servers'));
shuffle($s2);
$servers = implode(",", $s2);
$worker->addServers($servers); 

We run 6 to 10 workers at any time, and expire them after they've completed x requests.