Child processes

[simonhamp]

The Laravel side to the long-running process feature

Electron side: NativePHP/electron#115

Docs: NativePHP/nativephp.com#53

[XbNz]

Hey @simonhamp,

I was following this conversation and wasn't able to deduce whether you guys managed to come up with a proper inter-process communication mechanism.

My use case is that I'm listening to the native: channel in a Livewire component:

#[On('native:'.SomeCustomEvent::class)]

final class SomeCustomEvent implements ShouldBroadcastNow
{
    use Dispatchable;
    use InteractsWithSockets;

    public function broadcastOn(): array
    {
        return [
            new Channel('nativephp'),
        ];
    }
}

This works great when the event is dispatched from a queue worker (::dispatchSync() and ::dispatch(). However, when the event is fired from within a child process, it does not seem to hit my Livewire method. The only alternative to this would be polling with something like wire:poll, which isn't ideal.

I do see that you've had to implement some custom JavaScript to fire the (4?) pre-defined events dedicated to child processes:

    proc.stdout.on('data', (data) => {
        notifyLaravel('events', {
            event: 'Native\\Laravel\\Events\\ChildProcess\\MessageReceived',
            payload: {
                alias,
                data: data.toString(),
            }
        });
    });
    proc.stderr.on('data', (data) => {
        console.error('Error received from process [' + alias + ']:', data.toString());
        notifyLaravel('events', {
            event: 'Native\\Laravel\\Events\\ChildProcess\\ErrorReceived',
            payload: {
                alias,
                data: data.toString(),
            }
        });
    });
    proc.on('spawn', () => {
        console.log('Process [' + alias + '] spawned!');
        state.processes[alias] = {
            pid: proc.pid,
            proc,
            settings
        };
        notifyLaravel('events', {
            event: 'Native\\Laravel\\Events\\ChildProcess\\ProcessSpawned',
            payload: [alias, proc.pid]
        });
    });
    proc.on('exit', (code) => {
        console.log(`Process [${alias}] exited with code [${code}].`);
        notifyLaravel('events', {
            event: 'Native\\Laravel\\Events\\ChildProcess\\ProcessExited',
            payload: {
                alias,
                code,
            }
        });
        const settings = Object.assign({}, getSettings(alias));
        delete state.processes[alias];
        if (settings.persistent) {
            console.log('Process [' + alias + '] wathchdog restarting...');
            startProcess(settings);
        }
    });

So clearly, there is a manual process involved in making the parent PHP process aware of the child events. Btw, these work with Livewire! Is there a way you can accomodate for firing custom events on the nativephp channel from the child to the parent?

[SRWieZ]

Hey @XbNz!

You're correct, the only two ways to have inter-process communication are:

• Outputting text from the child process and receiving it by Native\Laravel\Events\ChildProcess\MessageReceived
• Using the Laravel event system. That will be fixed by Fix / Forward native ENV variables to child process electron#129

@gwleuverink just finished the fix, so it should be merged soon enough 😉

[XbNz]

• Outputting text from the child process and receiving it by Native\Laravel\Events\ChildProcess\MessageReceived

I completely neglected that as a possible solution. It's even described in the docs lol.

In that case, it'll be possible to create a long-running worker using something like ReactPHP's WritableStreamInterface to implement a loop that handles a JSON-encoded workload and sends the response to STDOUT. This might be overkill though, since custom event support is coming.

Thanks for the quick help.