Worker->fork() not working when pcntl isn't installed

[ruudk]

I just found out that my production server doesn't have PCNTL installed. Now every job is accepted but not executed:

// Resque/Worker.php

// On my server, this returns -1 because it isn't installed
$this->child = Resque::fork();

// So here, it isn't executed, because it isn't 0 nor false
if ($this->child === 0 || $this->child === false) {
    $status = 'Processing ' . $job->queue . ' since ' . strftime('%F %T');
    $this->updateProcLine($status);
    $this->log($status, self::LOG_VERBOSE);
    $this->perform($job);
    if ($this->child === 0) {
        exit(0);
    }
}

// This isn't executed either... because its below 0 
if($this->child > 0) {
    // Parent process, sit and wait
    $status = 'Forked ' . $this->child . ' at ' . strftime('%F %T');
    $this->updateProcLine($status);
    $this->log($status, self::LOG_VERBOSE);

    // Wait until the child process finishes before continuing
    pcntl_wait($status);
    $exitStatus = pcntl_wexitstatus($status);
    if($exitStatus !== 0) {
        $job->fail(new Resque_Job_DirtyExitException(
            'Job exited with exit code ' . $exitStatus
        ));
    }
}

$this->child = null;

// Wtf?? Didn't do anythin' ;)
$this->doneWorking();

So what would be the best way to fix this?

[rajibahmed]

Yes we have the same issue. It is related to #93
I think library can add required extension on composer file. Then everyone knows that you will need pcntl extension.

[richardkmiller]

I've fixed this in #94 by running the job in the parent if forking is not possible.

[richardkmiller]

OK, I like the approach in #93 better than my own, so I updated mine (#94) to match.

[rajibahmed]

But to me, if your system does not support forking via pcnlt. You will lose the benefit of using multiple workers at the same time. It is needed to spawn multiple workers.
We had the same issue recently using PCNLT on production. We did not install PCNLT on the application machine. We had separate VM with PCNTL installed and using created api to create jobs. I Know this may not relate to the problem.

My argument composer should force PCNLT extension check.

[ruudk]

Composer should indeed warn me about the dependency. I'll install PCNLT to get it working.

[danhunsaker]

So, could this issue be closed, then?

[richardkmiller]

FWIW, I agree with providing a warning in Composer since most people will run php-resque on *nix machines. However, I still like the patches in #93 or (my) #94 which allow php-resque to run even if it can't fork.

[danhunsaker]

I agree to a point - I'd prefer to have something similar to forking on non-forking systems that allows each job to be executed in an isolated space, where fatal errors won't bring the whole Resque engine down. There are a large number of other reasons to execute jobs in an isolated space, but most of them have to do with avoiding strange issues from pollution of the execution environment. If there was a way to process jobs in an isolated space that didn't rely on forking, but still provided the advantages we use forking for in the first place, I'd be all for it.

Until then, I'll just fall back on my standard (though somewhat rude) "Use a real OS". 😄

[richardkmiller]

Haha, can't disagree with that. :) (We also use php-resque on Ubuntu and it's great.)