Hello! I’ve been trying to create a simple Prometheus client for Julia. For this, I need to run a small web server inside my application, which does all sorts of computations. The problem is that the web server provided by HTTP.jl is concurrent, but not parallel, i.e., no web requests (Prometheus s…

A quick update on this. I had another go at my original probilem, and found a workaround. By explicitly allocating threads to the interactive as well as the default pool, and spawning the CPU consuming work on a default thread, I could get it to work as epxected: $ julia --threads=1,1 julia> using …

[image] tlienart: Note: hmm the info message by HTTP is that it’s listening on thread id: 1 which is odd given it was spawned on thread 2. Either I’m missing something or it’s a glitch from HTTP :thinking: It’s been a year or more since tasks could migrate to other threads. You shouldn’t rely…

[image] tlienart: Does this do what you want? I don’t see how your example demonstrates the server actually working on one thread while another thread is busy computing stuff. The HTTP server works fine from a second thread, except that it doesn’t respond while the main (interactive) thread i…

I probably misunderstood your question but with 3 threads and adding one task that does busy work you get similar stuff: if that’s not your point, I guess I’ll let someone else answer

After running some experiments and also going over the HTTP.jl documentation (especially related to how a non-blocking server is spawned), I concluded this is a Julia issue, not related at all to HTTP.jl package. Consider the following experiment: using Base.Threads using Dates interactive_channe…

I created a related topic here - as this doesn’t seem related to HTTP.jl package: [image] Bug in sleep() function - main thread work affecting sleep duration on running tasks General Usage What triggered the present experiment was my failure to find a reasonable solution …

[image] algunion: Conclusions: Spinning the main thread seems to block/delay communication between the other threads (that are doing naive/low computation). You can test this by running the calling longrunning() on the main thread (see comments in the code snippet). All works well if the longr…

[image] dlakelan: What happens if you call yield() in the main thread immediately after @spawn and then continue doing busy work in the main thread? I guess you’d get a different result? I already checked that - in different ways. For example - I can put the main to sleep for a few seconds un…

I also tried initiating the channel on a different thread (not the main one). The same result: the communication with the channel of tasks running on different threads than the main seems dependent on the free main thread. Please tell me that I made a mistake somewhere. This is crazy.

What happens if you make the channel have an explicit size, say 3? I wonder if Channel(Inf) is forcing it to do an allocation when you put! and the allocation is blocking until the main thread is pausable?

[image] dlakelan: EDIT: another issue might be contention over output resources. If the thing you’re trying to spawn is supposed to spew some stuff to stdout it might just block waiting to get a lock on the output or something similar. I hoped that is the culprit - this is why I designed my e…

How to run a HTTP.jl server in parallel, while doing computations in the foreground?

General Usage

dlakelan July 21, 2023, 10:37pm 17

for anyone else finding this for posterity, and to be super clear, the other thread is: Communication between tasks dependent on “free” main thread

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How to run a HTTP.jl server in parallel, while doing computations in the foreground?

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