ProcessManager.php

<?php

namespace Symbiote\QueuedJobs\Services;

use AsyncPHP\Doorman\Manager\ProcessManager as BaseProcessManager;
use SilverStripe\Core\Config\Configurable;

/**
 * Class ProcessManager
 *
 * customise shell command to allow child tasks to persist even after manager process is terminated
 * this lets the started jobs to finish properly in case the management process terminates
 * fore example there are no more jobs to start or queue is paused
 *
 * @package Symbiote\QueuedJobs\Services
 */
class ProcessManager extends BaseProcessManager
{
    use Configurable;

    /**
     * Enable / disable persistent child process
     * If this is enabled the child processes can outlive the parent (manager process)
     * This is what is needed for most cases as the manager process only starts new child processes
     * Child processes on the other hand, actually execute queued jobs so they may take longer to execute
     * Disabling this may cause the child processes to terminate prematurely which may result it multiple job
     * execution retries / resumes
     * Disable this option only if you are debugging a situation when a child process
     * keeps hanging around for way too long (hours)
     * Adding execution timeout to individual queued jobs is recommended to avoid such situation
     *
     * @config
     * @var bool
     */
    private static $persistent_child_process = true;

    /**
     * @param string $binary
     * @param string $worker
     * @param string $stdout
     * @param string $stderr
     * @return string
     */
    protected function getCommand($binary, $worker, $stdout, $stderr) // phpcs:ignore SlevomatCodingStandard.TypeHints
    {
        // Nohup is short for “No Hangups.” It’s not a command that you run by itself.
        // Nohup is a supplemental command that tells the Linux system not to stop another command once it has started.
        // That means it’ll keep running until it’s done, even if the user that started it logs out
        // Nohup is used here because the queue management process runs in a loop and it's starting new child processes
        // which are running jobs
        // It's possible to have the situation when queue management process terminates as it's no longer needed
        // to create any new child processes but we still want the existing child processes to continue their work
        // and finish the jbos which are already running
        return sprintf('nohup %s %s %%s %s %s & echo $!', $binary, $worker, $stdout, $stderr);
    }

    public function __destruct()
    {
        if ($this->config()->get('persistent_child_process')) {
            // Prevent background tasks from being killed when this script finishes
            // this is an override for the default behaviour of killing background tasks
            return;
        }

        parent::__destruct();
    }
}