[druid-user] Broker resultLevel cache - only cache misses

Apache Druid Q&A Google Groups
#1

Hi everybody,

I have the following config for the brokers:

druid.broker.cache.populateCache=false
druid.broker.cache.populateResultLevelCache=true
druid.broker.cache.useCache=false
druid.broker.cache.useResultLevelCache=true

And on the historicals:

druid.historical.cache.populateCache=true
druid.historical.cache.useCache=true

The per-segment cache works really nicely on historicals, but I only
see cache misses reported by the broker (where IIUC I am using only
the ResultLevel cache for whole queries), and the cache size doesn't
grow at all. I am wondering if I need to adjust any setting, I used
the config suggested in
https://druid.apache.org/docs/latest/querying/caching.html:

Brokers support both segment-level and whole-query result level caching. Segment-level caching is controlled by the parameters useCache and populateCache. Whole-query result level caching is controlled by the parameters useResultLevelCache and populateResultLevelCache and runtime properties druid.broker.cache.*.

Is there anything that I am missing or is it all related to my query patterns?

Thanks in advance!

Luca

#2

I found Group By V2 query should use the Query/result level cache, if enabled at Broker. · Issue #10344 · apache/druid · GitHub, and I am
wondering where to find documentation about what queries are cacheable
in whole-query/result-level Broker cache. Looking into the code is not
that easy :smiley:

Thanks in advance,

Luca

#3

After a lot of research, I think that the issue is probably
[DRAFT] 0.20.0 Release Notes · Issue #10462 · apache/druid · GitHub (I am
running 0.19).

Luca

#4

Thanks for updating this Q!

I would be interested to know what impact this gives you on query times when if / you have it working?