hey I'm struggling to find documentation around setting java heap settings, specifically when running the questdb container, can anyone point me at an example/docs?

@Jaromir Hamala could you steer @Kurt to the right docs? thanks!

Sure thing! Hello Kurt, are you interested in a guide how to size your heap or how to actually set a Java heap inside a container to a specific value? I’m afraid we do not have a step-by-step guide to follow. QuestDB is designed to be extremely conservative with on-heap memory allocations and it usually does not require heap tuning. Most of our memory allocations are outside of the Java heap. I see we do not set heap size explicitly in our docker container hence it relies on JVM ergonomics. Are you having issues with Java heap?

potentially having issues with heap - wanted to tune as part of debugging. nevermind then

can you please be more specific? are you observing slowdowns? or OOM exceptions? or perhaps suspicious metrics?

OOMs

Could you share crash dump file or specific error message ?

also: if you want to experiment with explicit heap sizing then you can pass arguments to your container - our

docker-entrypoint-sh

will pass them to JVM. so you can try things like

docker run questdb/questdb -Xmx5g -m io.questdb/io.questdb.ServerMain -d /var/lib/questdb

You could add something like `

-XX:+HeapDumpOnOutOfMemoryError -XX:HeapDumpPath=/some/mount/dir/from/your/host"

to allow further investigation. You could also consider enabling the verbose GC log - to see what the heap usage pattern look like.

thanks - i can't get it right now but i may have another look tomorrow

I created https://github.com/questdb/questdb/issues/3401 to make heap (and other) changes simpler. so thank you for raising this!