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.