OutofMemoryErrors

[Tom N]

6 node MapR cluster with 4 nodes running OpenTSDB 2.3.0.

Grafana is the primary client pulling data and lately we've been getting a lot of out of memory errors but are having a hard time nailing down the root cause. 

Where can I look to get more information in order to troubleshoot more? This is about the only page I can find on this: http://opentsdb.net/docs/build/html/user_guide/troubleshooting.html

Exception: java.lang.OutOfMemoryError thrown from the UncaughtExceptionHandler in thread "pool-1-thread-64"

Exception in thread "pool-1-thread-1" Exception in thread "pool-1-thread-9" java.lang.OutOfMemoryError: Java heap space

java.lang.OutOfMemoryError: Java heap space

Thanks for any help you can provide.