[dev] Database access in process fork (Jan Schneider)

[Ian Roth]

> Zitat von Ian Roth <iron_hat at hotmail.com>:
>
>> I have a cron script that takes requests from a queue and makes
>> calls to cloud service based on those queued requests. These API
>> calls can take a long time to receive a response, and under heavy
>> load it would be nice to be able to use one process per request. The
>> trouble I am having is that using pcntl_fork() causes child
>> processes to use the same Horde_Db instance as the parent, and this
>> causes exceptions when multiple child processes attempt to write a
>> response back to the database. What is the best approach: creating a
>> new Horde_Db instance in each child process, or
>> using?semaphore?between child processes to avoid resource deadlock?
>> Here is the code I have so far, and it can be modified at this
>> url:?https://gist.github.com/3154317
>
> You could either use a separate Horde_Db instance for each process or
> use some locking mechanism to avoid concurrent access. The choice
> probably depends on whether you need to scale this application with
> time constraints or resource constraints.

I think I will treat this problem as time constrained. How do I force the driver factory to give a new instance each time it is requested? I based the code after the SQL driver code found in the skeleton application.

>
>> #!/usr/bin/env php
>> <?php
>>
>> $baseFile = __DIR__ . '/../lib/Application.php';
>> if (file_exists($baseFile)) {
>> ????require_once $baseFile;
>> }
>> Horde_Registry::appInit(<app>, array('authentication' => false,
>> 'cli' => true));
>>
>> $driver =
>> $GLOBALS['injector']->getInstance('<app>_Factory_Driver')->create();
>> $processes = $driver->getProcessestoStart();
>>
>> foreach($processes as $process) {
>> ????$pid = pcntl_fork();
>> ????if ($pid == -1) { // Error in forking
>> ????????throw new <app>_Exception('Unable to fork.');
>> ????} elseif ($pid) { // Parent process
>>
>> ????} else { // End process
>> ????????start_process($process);
>> ????????exit;
>> ????}
>> }
>>
>> function start_process($process) {
>> ????$driver =
>> $GLOBALS['injector']->getInstance('<app>_Factory_Driver')->create();
>>
>> ????require_once 'AWSSDKforPHP/sdk.class.php';
>> ????$ec2 = new AmazonEC2(array('key' =>
>> $GLOBALS['conf']['aws']['key'], 'secret' =>
>> $GLOBALS['conf']['aws']['secretkey']));
>>
>> ????$response = $ec2->create_key_pair($process['key_name']);
>> ????$driver->addClusterLog($process['cluster_id'], $response);
>>
>>
>> Regards,
>> Ian
>
>
> --
> Jan Schneider
> The Horde Project
> http://www.horde.org/