How does FrankenPHP handle sleeping / thread autoscaling / workers?

[Vectorial1024]

I am trying to understand the performance profile of FrankenPHP, and came across a scenario which I am not sure about.

Imagine a FrankenPHP instance with 10 workers and no thread autoscaling. Suppose all 10 workers decide to call PHP sleep(10) at the same time. Then, because thread autoscaling is disabled, does this mean FrankenPHP during this time will queue incoming web requests until the sleep calls complete and some workers become available again?

Similarly, if thread autoscaling is enabled, when all workers are unavailable (e.g. by sleep), will FrankenPHP spawn more threads to serve incoming new requests? Or is request handling capped by the number of workers no matter what happens so spawning more threads does not help (because all workers are busy at sleep)?

[AlliBalliBaba]

Yes when there are 10 threads and no autoscaling, the maximum number of requests PHP can handle is 10. All other requests will be queued until a PHP thread becomes free. You can also configure max_wait_time to set how long these requests are allowed to wait for a thread before just being rejected with 503.

If you have max_threads (autoscaling) configured, new threads will be spawned up to that limit as long as requests are queued for long enough. So the maximum number of concurrent requests PHP can handle is max_threads.

If you have certain requests that are interacting with a very slow external API, you can also split the threadpool by path to limit concurrency to certain endpoints.

[Vectorial1024]

Thanks for the answer.

From the docs, being able to split the thread pool should greatly help with overall performance. Indeed some endpoints are "heavy" and expected to be slower than usual, so ideally they should be split to not block the other "lightweight" endpoints.

[dunglas]

It could be nice to add these details to the docs!

[Vectorial1024]

The idea of improving the docs is good, but I can't think of how the information in this question may be used to improve the docs.