Laravel Horizon is scaling the wrong way (auto + max-processes)

[michabbb]

hi all,

i am very surprised i am unable to find anything about that issue.
laravel horizon is scaling - at least for me - completely wrong.
that means every supervisor starts as many workers as "max-processes" from the horizon config.

as seen here:
https://github.com/laravel/horizon/blob/d4e24a9cfff8cacfa44c75ca0ac759984f152d1c/src/Console/SupervisorCommand.php#L97

but that makes no sense at all. let´s say I have 5 supervisors, each with max-processes of 50 and an empty queue.
so why should I start 250 workers to scale them immediately down to 5 (min-processes).

pardon, for me, a scaler should always start as low as possible and scale up ONLY if needed, not the other way around.

so the specific line of code I am referring to should be like this:

  $supervisor->scale(1);

with that, horizon only starts 1 worker for each supervisor and only scales up to "max-processes" if really needed.

you can argue: what´s the problem? you should never run more workers than your host is able to run. so in the worst case, you are running a few seconds on max load of your host before everything gets scaled down.

but for me, this is more a thing of "good principals", and don´t waste any resources if you don´t need to.
and some people may over-provision their queues. means: the host is on limit when running all queues on max,
but this usually never should happen. but with the current (auto) "scale" concept of horizon: when horizon starts,
the host is always on max load even when the queue is empty, and that makes no sense at all.

i would be happy if we could change that. but I have no idea where I have to address that issue.
i think another option in the horizon config like always_start_with_one => true could solve that issue easily.

what do you think ?

thanks,
micha

[henzeb]

I agree. Makes no sense.

[henzeb]

Not much going on here. Maybe @driesvints @nunomaduro or @taylorotwell can elaborate on this? is there a reason why we start horizon full throttled?

[michabbb]

looks like nobody is using horizon 🤷

[jrafael29]

i think, you can set autoScalingStrategy = size, on horizon config file, in supervisor's config

[michabbb]

as long this code exists:

https://github.com/laravel/horizon/blob/295b4bcb713a62eb86d83951e291f7481bc24a28/src/Console/SupervisorCommand.php#L96C32-L98

        $supervisor->scale(max(
            0, $this->option('max-processes') - $supervisor->totalSystemProcessCount()
        ));

nothing helps. because at the moment horizon is stating it scales to max and then scales down after, that´s the issue.
every 3 year old understands that this is nonsense - but mr lambo himself thinks it´s a great idea.... nothing more to say 🙄 🤷 😞

[fragkp]

Maybe create a PR instead of complaning like an idiot? nothing more to say

[michabbb]

@fragkp It is no shame to be illiterate, but to flaunt it like that is embarrassing.

[fragkp]

Your answer to me is the reason that your "PR" is not merged.

[michabbb]

@fragkp Thanks for confirming that you’re unable to read anything, but at least you enriched the world with your meaningful comments, congratulations. 👏

[bulletproof-coding]

@michabbb I saw your PR.

A reason might be that when you deploy in full load, you don't want a hiccup exactly after the deploy process.

Correct me if I am wrong, but that formula from there assures the already working processes are subtracted from the max amount and only the difference is started, resulting in total = max number (that is already auto for me).

There are 3 cases here.

Max 10
Already working 1 to 9
start 9 to 1 more

Max 10
Already working 0
start 10 more

Max 10
Already Working 10
Start 0 new.

Based on this if you are fully loaded at deploy, then 0 are started (I am not familiar with how the rest will be started after the old container shuts down). This might be considered more important than this other case:

You are with empty queue and you will start the difference until full, then scale down.

Now if the difference is closer to max => smaller load.
If the difference is farther away from max => bigger load.

[bulletproof-coding]

@michabbb #49633 (comment) FYI supervisord is not aware of signals. I found an alternative.