* Cache: Add maxEntrySize config.
The idea is this makes it more feasible to cache query types that
can potentially generate large result sets, like groupBy and select,
without fear of writing too much to the cache per query.
Includes a refactor of cache population code in CachingQueryRunner and
CachingClusteredClient, such that they now use the same CachePopulator
interface with two implementations: one for foreground and one for
background.
The main reason for splitting the foreground / background impls is
that the foreground impl can have a more effective implementation of
maxEntrySize. It can stop retaining subvalues for the cache early.
* Add CachePopulatorStats.
* Fix whitespace.
* Fix docs.
* Fix various tests.
* Add tests.
* Fix tests.
* Better tests
* Remove conflict markers.
* Fix licenses.
* remove ServerConfig from DruidNode as all information needs to be present in DruidNode serialized form
* sanitize output of /druid/coordinator/v1/cluster endpoint
This patch introduces a GroupByStrategy concept and two strategies: "v1"
is the current groupBy strategy and "v2" is a new one. It also introduces
a merge buffers concept in DruidProcessingModule, to try to better
manage memory used for merging.
Both of these are described in more detail in #2987.
There are two goals of this patch:
1. Make it possible for historical/realtime nodes to return larger groupBy
result sets, faster, with better memory management.
2. Make it possible for brokers to merge streams when there are no order-by
columns, avoiding materialization.
This patch does not do anything to help with memory management on the broker
when there are order-by columns or when there are nested queries. That could
potentially be done in a future patch.
Gian Merlino
Himanshu
Parag Jain
Jonathan Wei
fjy
Xavier Léauté