gianm commented on a change in pull request #8116: remove unnecessary lock in ForegroundCachePopulator leading to a lot of contention URL: https://github.com/apache/incubator-druid/pull/8116#discussion_r305607537
########## File path: docs/content/configuration/index.md ########## @@ -1319,6 +1321,8 @@ You can optionally only configure caching to be enabled on the Historical by set |`druid.historical.cache.useCache`|true, false|Enable the cache on the Historical.|false| |`druid.historical.cache.populateCache`|true, false|Populate the cache on the Historical.|false| |`druid.historical.cache.unCacheable`|All druid query types|All query types to not cache.|["groupBy", "select"]| +|`druid.historical.cache.numBackgroundThreads`|If greater than 0, cache will be populated in the background thread pool of the configured size|0| Review comment: I thought there was some reason that background cache population wasn't documented. IIRC it was broken somehow (something about generating corrupt / incorrect cached data). But unfortunately I can't remember what was wrong or if it has been fixed yet. If it turns out that the feature _does_ work now, I believe it still does have one serious flaw — no load shedding means it can lead to your JVM running OOM. IMO, if we think the feature is still broken (in the sense that it corrupts caches), let's _not_ document it. If we think the feature works but has this potential OOM issue, then I think it's OK to document it, but the docs should call out the potential for OOMs due to lack of load shedding. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: us...@infra.apache.org With regards, Apache Git Services --------------------------------------------------------------------- To unsubscribe, e-mail: commits-unsubscr...@druid.apache.org For additional commands, e-mail: commits-h...@druid.apache.org
