Run as a worker process

[lokhman]

First of all, thank you for a fantastic library!

My question is related to running the cron scheduler as a so called "clock" process in Heroku. Heroku instances don't have crontab. In order to start cron:run every minute, you need to have a kind of worker "daemon" process which never dies. One possible example of such process is here: https://devcenter.heroku.com/articles/php-workers.

Is there any possible way of starting cron:run as a worker process? If there is none, will it be hard to add this functionality, as it will be very helpful in such services as Heroku.

Thanks!

[NoUseFreak]

Hi @lokhman! Thanks for using and trusing this project :-).
At the moment it's not possible to run this in daemon mode. I would love to add this as I like the feature! Maybe there are already other projects allowing you to get this behaviour but it feels like something this project can provide.

I would suggest implementing a -d flag on cron:run to make it start in daemon mode.
As my schedule is really packed at the moment, feel free to implement it.
Maybe https://reactphp.org/event-loop/ is a good starting point to get this working.

Feel free to ask any questions you want answered. I'll try to get back to you quicker than I did just now.

[lokhman]

Thank you, @NoUseFreak, for the reply!

As this feature was not available in the library and I needed a fast solution to embed one in the project, I wrote a very simple console script, which so far works very well:

#!/usr/bin/env php
<?php

use Symfony\Component\Process\Process;

umask(0000);
set_time_limit(0);

require __DIR__.'/../vendor/autoload.php';

$process = new Process(__DIR__.'/console cron:run');
$process->setTimeout(0);

while (true) {
    $now = microtime(true);
    usleep((60 - ($now % 60) + (int) $now - $now) * 1e6);

    if (!$process->isRunning()) {
        $process->start();
    }
}

This behaves like a synchronous crontab, which runs cron:run command exactly every minute (0 * * * *). Saying "synchronous" I mean that if a command gets executed for more than a minute, it will skip the next execution. In my project this will never happen, although making it asynchronous should not be a big problem.

I was also looking at event-loop library, but thought that probably for this kind of task utilising a full-featured event extension is a bit of an overkill, which will require an extra dependency. Component symfony/process has enough functionality to execute commands asynchronously, while making a simple queue should be a trivial task. What do you think? Is there anything I'm missing?