Error extending GearmanClient class - php

Question

Im trying to create a class extending GearmanClient so i can centralize and use gearman across my app according to my own specifications. One of the reasons im doing my own class is to store easily failed tasks into a database so they can be later processed again.
Im getting a basic error
Warning: GearmanClient::runTasks():
_client_run_task(GEARMAN_NO_SERVERS) no servers added -> libgearman/run.cc:66 in /var/www/html/app/forecast/Forecast.php on
line 37
<?php
namespace app\service;
use helpers\Config_helper;
use \GearmanClient;
class Gearman_service extends GearmanClient
{
public $client;
private $servers = array();
private $tasks = array();
private $completedTasks = array();
private $failedTasks = array();
private $maxRetryAttempts;
public function __construct()
{
$this->client = new GearmanClient();
$this->servers = Config_helper::get_config_option('gearman_servers');
$this->maxRetryAttempts = Config_helper::get_config_option('gearman_retry_attempts');
$this->initialize();
}
protected function initialize()
{
foreach($this->servers as $key => $value):
$this->client->addServer($value[0],$value[1]);
endforeach;
}
}
I must assume something is wrong with this implementation but i would like to know why.
The Config_helper::get_config_option('gearman_servers'); is retrieving correctly my list of servers.
This is my Forecast class
<?php
namespace app\forecast;
use app\service\Gearman_service;
use helpers\Config_helper;
use helpers\Urlrequest_helper;
use app\warehouse\models\Client_time_forecast;
abstract class Forecast
{
public $coordinates = array(); # set of coordinates
public $servers = array();
public $variables = array();
public $url = array();
public $prevision;
public $client;
public $gearmanclient;
public function __construct()
{
$this->servers = Config_helper::get_config_option('forecast_servers');
$this->variables = Config_helper::get_config_option('surface_variables');
$this->prevision = Config_helper::get_config_option('forecast_prevision');
$this->gearmanclient = new Gearman_service();
}
public function storeResults()
{
$this->gearmanclient->setCompleteCallback(array($this, 'requestComplete'));
foreach($this->url as $key => $value):
$this->gearmanclient->addTask('request_forecast', serialize($value[0]));
endforeach;
$this->gearmanclient->runTasks(); // **line 37**
}
/**
* [requestComplete store request results in cassandra db]
* #param \GearmanTask $task [description]
* #return [boolean]
*/
public function requestComplete(\GearmanTask $task)
{
$persistent = new Client_time_forecast($this->client, unserialize($task->data()));
$persistent->storeData();
}
}
Anyone can share me a light on this?
Thank you!

Answer 1

As suspected the cause of the problem is that you are mixing inheritance and composition. You extended the GearmanClient class and at the same time you are creating a new instance of the GearmanClient class in the constructor and configuring this new instance in method initialize.
class Gearman_service extends GearmanClient
{
public $client;
// other properties
public function __construct()
{
$this->client = new GearmanClient();
// more code
$this->initialize();
}
You could change the line 37 and all other calls to GermanClient public methods to call the instance initiated in constructor and do not extend GearmanClient class.
$this->gearmanclient->client->runTasks();
However it would be better to change visibility of the property Gearman_service::client to private and implement GeamanClient class public interface.
class Gearman_service extends GearmanClient
{
private $client;
// constructor etc
public function addTask($name, $workload, $context = null, $unique = "")
{
return $this->client->addTask($name, $workload, $context, $unique);
}
If you do so the line 37 should stay as it is.
Alternatively you could opt for inheritance. In that case you would need to remove public property client, do not create a new instance of the GeamanClient class in the constructor and change initialize methods.
protected function initialize()
{
foreach($this->servers as $key => $value):
$this->addServer($value[0],$value[1]);
endforeach;
}
In this case as well you don't need to change the line 37 nor any other calls GeamanClient class public methods.