Hi! I have been checking heap dump for Druid Historical process that exited due to OutOfMemory error. It looks

org.apache.druid.client.cache.CaffeineCache

took 32476592624 (~32GB) bytes while my config is set to

druid.cache.sizeInBytes=25769803776

(~25GB). I am running Druid version 31.0.1. What could be the reason of Druid cache going beyond specified limit?

The

druid.cache.sizeInBytes

limits the aggregate size of all cached data, but it doesn't track the overheads of the Caffeine map data structures. It is possible those take up significant space when the cached data is 25 GB. I'd try setting

druid.cache.sizeInBytes

lower to account for this, and see if you still have problems

Thanks! That's what we did and it helped. Would be useful to have a rough guideline on the size of the overhead though.