Details
-
Bug
-
Status: Resolved
-
Critical
-
Resolution: Fixed
-
3.4.0
-
Reviewed
Description
Standby NameNode crashes when transitioning to Active with a in-progress tailer. And the error message like blew:
Caused by: java.lang.IllegalStateException: Cannot start writing at txid X when there is a stream available for read: ByteStringEditLog[X, Y], ByteStringEditLog[X, 0]
at org.apache.hadoop.hdfs.server.namenode.FSEditLog.openForWrite(FSEditLog.java:344)
at org.apache.hadoop.hdfs.server.namenode.FSEditLogAsync.openForWrite(FSEditLogAsync.java:113)
at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.startActiveServices(FSNamesystem.java:1423)
at org.apache.hadoop.hdfs.server.namenode.NameNode$NameNodeHAContext.startActiveServices(NameNode.java:2132)
... 36 more
After tracing and found there is a critical bug in EditlogTailer#catchupDuringFailover() when DFS_HA_TAILEDITS_INPROGRESS_KEY is true. Because catchupDuringFailover() try to replay all missed edits from JournalNodes with onlyDurableTxns=true. It may cannot replay any edits when they are some abnormal JournalNodes.
Reproduce method, suppose:
- There are 2 namenode, namely NN0 and NN1, and the status of echo namenode is Active, Standby respectively. And there are 3 JournalNodes, namely JN0, JN1 and JN2.
- NN0 try to sync 3 edits to JNs with started txid 3, but only successfully synced them to JN1 and JN2
JN3. And JN0 is abnormal, such as GC, bad network or restarted. - NN1's lastAppliedTxId is 2, and at the moment, we are trying failover active from NN0 to NN1.
- NN1 only got two responses from JN0 and JN1 when it try to selecting inputStreams with fromTxnId=3 and onlyDurableTxns=true, and the count txid of response is 0, 3 respectively. JN2 is abnormal, such as GC, bad network or restarted.
- NN1 will cannot replay any Edits with fromTxnId=3 from JournalNodes because the maxAllowedTxns is 0.
So I think Standby NameNode should catchupDuringFailover() with onlyDurableTxns=false , so that it can replay all missed edits from JournalNode.
