Major Description
This happens if the RS is restarted before the zk node expires. The sequence is as follows:
1. RS1 dies - lets say its server string was HOST1:PORT1:TS1
2. In a few seconds RS1 is restarted, it comes up as HOST1:PORT1:TS2 (TS2 is more recent than TS1)
3. Master gets a start up message from RS1 with the server name as HOST1:PORT1:TS2
4. Master adds this as a new RS, tries to red
---- The master does not use the generation stamps to detect that RS1 has already restarted.
---- Also, if RS1 contained meta, master would try to go to HOST1:PORT1:TS1. It would end up talking to HOST1:PORT1:TS2, which spews a bunch of not serving region exceptions.
5. zk node expires for HOST1:PORT1:TS1
6. Master tries to process shutdown for HOST1:PORT1:TS1 - this probably interferes with HOST1:PORT1:TS2 and ends up somehow removing the reassign meta in the master's queue.
---- Meta never comes online and master continues logging the following exception indefinitely:
2010-04-06 11:02:23,988 DEBUG org.apache.hadoop.hbase.master.HMaster: Processing todo: ProcessRegionClose of test1,7094000000,1270220428234, false, reassign: true
2010-04-06 11:02:23,988 DEBUG org.apache.hadoop.hbase.master.ProcessRegionClose$1: Exception in RetryableMetaOperation:
java.lang.NullPointerException
at org.apache.hadoop.hbase.master.RetryableMetaOperation.doWithRetries(RetryableMetaOperation.java:64)
at org.apache.hadoop.hbase.master.ProcessRegionClose.process(ProcessRegionClose.java:63)
at org.apache.hadoop.hbase.master.HMaster.processToDoQueue(HMaster.java:494)
at org.apache.hadoop.hbase.master.HMaster.run(HMaster.java:429)