I’m having a very frustrating issue debugging something, and I’m now resorting to the forum for help. I’m sure people will recognize this question as I’ve exhausted a lot of options trying to solve it. I have an API that currently gets ~100,000 incoming requests/minute (1,600 RPS). For each incomi…

Second follow up question. You said I would have to ‘trace a function’. What’s the best tool to actually do that? I see like 10 versions of different ‘prof’ like cprof, dprof, eprof, etc etc. I have no idea which one would be best for this use case (I would probably trace the very top of the executi…

Hackney exposes very detailed metrics GitHub - benoitc/hackney: simple HTTP client in Erlang · GitHub , Specially hackney.POOLNAME.queue_counter can be very useful in determining whether timeouts are due to pool size.

you can remove pool and see what you get. you will certainly be slower but at least you will be getting to the amount actual sockets possible. You will also figure out what goes first - CPU, network bandwidth. Pool usage in this case is probably a good thing for you as it provides for some pushback…

I tried without it and it was crazy low. are you saying thats the exact amount that its limited by an external resource?

Hi, Sorry a bit late here. I worked on the adserver at Yieldbot and it had no issues handling 10,000 QPS on 6 instances (or was it 9) using IIRC 8 cpus servers with each instance using about 1G of ram. This should be doable. The servers were CPU bound not ram or network bound. We were running our …

Wow this is super advice. A few questions… Were these outgoing requests (10K/S)? or incoming. what http library did you use? Did you have any wisdom for choosing the pool settings? My main confusion right now is how to calculate the max pool size per instance… like the CPU chart doesn’t cle…

You’re welcome. :slight_smile: Incoming requests. We did make a request to a server on the local network on each incoming request so both. (As well as cache requests to scylladb.) We used HTTPoison and Tesla. Both were configured to use hackney. (IIRC hackney handled https connections better, …

scylladb looks amazing. very interesting, thank you. So basically when you see MsgQ backup that means schedulers are the holdup and not the actual server CPU/resources? Very interesting… this is very helpful, in my project but also just general understanding

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Difficult debugging problem

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ashneyderman December 30, 2018, 6:30am 76

it could be, what is crazy low (i mean quantitatively)?