In this recipe, we will describe how to troubleshoot the following ZooKeeper session expired error shown in the RegionServer logs:
2012-02-19 16:49:15,405 WARN org.apache.hadoop.hbase.regionserver.HRegionServer: Failed deleting my ephemeral node
org.apache.zookeeper.KeeperException$SessionExpiredException: KeeperErrorCode = Session expired for /hbase/rs/ip-10-168-37-91.us-west-1.compute.internal,60020,1329635463251 at org.apache.zookeeper.KeeperException.create(KeeperException.java:127) at org.apache.zookeeper.KeeperException.create(KeeperException.java:51) at org.apache.zookeeper.ZooKeeper.delete(ZooKeeper.java:868) at org.apache.hadoop.hbase.zookeeper.RecoverableZooKeeper.delete(RecoverableZooKeeper.java:107)
This issue is critical, because master or region servers will shut themselves down if they lose connection to the ZooKeeper quorum.