[HBASE-20921] Possible NPE in ReopenTableRegionsProcedure

• Type: Sub-task
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 3.0.0-alpha-1, 2.1.0, 2.0.2
• Fix Version/s: 3.0.0-alpha-1, 2.2.0, 2.1.1, 2.0.2
• Component/s: amv2
• Assignee: Allan Yang
• Reporter: Allan Yang
• Created: 23/Jul/18 12:52
• Updated: 04/Mar/19 09:07
• Resolved: 27/Jul/18 01:40

Description

After HBASE-20752， we issue a ReopenTableRegionsProcedure in ModifyTableProcedure to ensure all regions are reopened.
But, ModifyTableProcedure and ReopenTableRegionsProcedure do not hold the lock (why?), so there is a chance that while ModifyTableProcedure executing, a merge/split procedure can be executed at the same time.
So, when ReopenTableRegionsProcedure reaches the state of "REOPEN_TABLE_REGIONS_CONFIRM_REOPENED", some of the persisted regions to check is actually not exists, thus a NPE will throw.

2018-07-18 01:38:57,528 INFO  [PEWorker-9] procedure2.ProcedureExecutor(1246): Finished pid=6110, state=SUCCESS; MergeTableRegionsProcedure table=IntegrationTestBigLinkedList, regions=[845d286231eb01b7
1aeaa17b0e30058d, 4a46ab0918c99cada72d5336ad83a828], forcibly=false in 10.8610sec
2018-07-18 01:38:57,530 ERROR [PEWorker-8] procedure2.ProcedureExecutor(1478): CODE-BUG: Uncaught runtime exception: pid=5974, ppid=5973, state=RUNNABLE:REOPEN_TABLE_REGIONS_CONFIRM_REOPENED; ReopenTab
leRegionsProcedure table=IntegrationTestBigLinkedList
java.lang.NullPointerException
        at org.apache.hadoop.hbase.master.assignment.RegionStates.checkReopened(RegionStates.java:651)
        at java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:193)
        at java.util.ArrayList$ArrayListSpliterator.forEachRemaining(ArrayList.java:1382)
        at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:481)
        at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:471)
        at java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:708)
        at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
        at java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:499)
        at org.apache.hadoop.hbase.master.procedure.ReopenTableRegionsProcedure.executeFromState(ReopenTableRegionsProcedure.java:102)
        at org.apache.hadoop.hbase.master.procedure.ReopenTableRegionsProcedure.executeFromState(ReopenTableRegionsProcedure.java:45)
        at org.apache.hadoop.hbase.procedure2.StateMachineProcedure.execute(StateMachineProcedure.java:184)
        at org.apache.hadoop.hbase.procedure2.Procedure.doExecute(Procedure.java:850)
        at org.apache.hadoop.hbase.procedure2.ProcedureExecutor.execProcedure(ProcedureExecutor.java:1453)
        at org.apache.hadoop.hbase.procedure2.ProcedureExecutor.executeProcedure(ProcedureExecutor.java:1221)
        at org.apache.hadoop.hbase.procedure2.ProcedureExecutor.access$800(ProcedureExecutor.java:75)
        at org.apache.hadoop.hbase.procedure2.ProcedureExecutor$WorkerThread.run(ProcedureExecutor.java:1741)

I think we need to renew the region list of the table at the "REOPEN_TABLE_REGIONS_CONFIRM_REOPENED" state. For the regions which are merged or split, we do not need to check it. Since we can be sure that they are opened after we made change to table descriptor.

Issue Links

• is related to: HBASE-21078 [amv2] CODE-BUG NPE in RTP doing Unassign