Solr for Audit setup doesn't use DocValues effectively

Ranger uses Ambari Infra Solr (or another Apache Solr install) for storing Ranger Audit events for displaying in Ranger Admin. In our case, we have noticed quite a few Ambari Infra Solr OOM due to Ranger. I've talked with a few other people who are having very similar problems with OOM errors.

I've typed up some details about how the way Ranger is using Solr requires a lot of heap. I've also outlined the fix for this which significantly reduced the amount of heap memory required. I'm an Apache Lucene/Solr committer so this optimization/usage might not be immediately obvious to those using Solr especially version 5.x.

https://risdenk.github.io/2017/12/18/ambari-infra-solr-ranger.html