https://builds.apache.org/job/Lucene-Solr-NightlyTests-6.x/126/
Looks like there are lots of lines like: [junit4] HEARTBEAT J0 PID(530@lucene1-us-west): 2016-07-26T02:10:40, stalled for 272592s at: HdfsCollectionsAPIDistributedZkTest.test Kevin Risden
