NN stopped and cannot recover with error "There appears to be a gap in the edit log"

[#1]

Hi there,

I deployed a single node for CDH and CM for testing, however once I added some services like Hub, the NN stopped and cannot start it with eror: There appears to be a gap in the edit log.

2013-11-14 15:00:01,431 INFO org.apache.hadoop.metrics2.impl.MetricsSystemImpl: NameNode metrics system shutdown complete.
2013-11-14 15:00:01,432 FATAL org.apache.hadoop.hdfs.server.namenode.NameNode: Exception in namenode join
java.io.IOException: There appears to be a gap in the edit log.  We expected txid 8364, but got txid 27381.
	at org.apache.hadoop.hdfs.server.namenode.MetaRecoveryContext.editLogLoaderPrompt(MetaRecoveryContext.java:94)
	at org.apache.hadoop.hdfs.server.namenode.FSEditLogLoader.loadEditRecords(FSEditLogLoader.java:158)
	at org.apache.hadoop.hdfs.server.namenode.FSEditLogLoader.loadFSEdits(FSEditLogLoader.java:92)
	at org.apache.hadoop.hdfs.server.namenode.FSImage.loadEdits(FSImage.java:744)
	at org.apache.hadoop.hdfs.server.namenode.FSImage.loadFSImage(FSImage.java:660)
	at org.apache.hadoop.hdfs.server.namenode.FSImage.doUpgrade(FSImage.java:349)
	at org.apache.hadoop.hdfs.server.namenode.FSImage.recoverTransitionRead(FSImage.java:261)
	at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.loadFSImage(FSNamesystem.java:639)
	at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.loadFromDisk(FSNamesystem.java:476)
	at org.apache.hadoop.hdfs.server.namenode.NameNode.loadNamesystem(NameNode.java:403)
	at org.apache.hadoop.hdfs.server.namenode.NameNode.initialize(NameNode.java:437)
	at org.apache.hadoop.hdfs.server.namenode.NameNode.(NameNode.java:613)
	at org.apache.hadoop.hdfs.server.namenode.NameNode.(NameNode.java:598)
	at org.apache.hadoop.hdfs.server.namenode.NameNode.createNameNode(NameNode.java:1169)
	at org.apache.hadoop.hdfs.server.namenode.NameNode.main(NameNode.java:1233)
2013-11-14 15:00:01,445 INFO org.apache.hadoop.util.ExitUtil: Exiting with status 1
2013-11-14 15:00:01,448 INFO org.apache.hadoop.hdfs.server.namenode.NameNode: SHUTDOWN_MSG: 
/************************************************************
SHUTDOWN_MSG: Shutting down NameNode at ubcdh/10.0.0.4
************************************************************/

I tied to run "./bin/hadoop namenode -recover" however it was returned another error:

13/11/14 14:52:17 INFO hdfs.StateChange: STATE* Safe mode is ON.
Use "hdfs dfsadmin -safemode leave" to turn safe mode off.

 However the command to leave safemode with error:

safemode: Call From ubcdh/10.0.0.4 to ubcdh:8020 failed on connection exception: java.net.ConnectException: Connection refused; For more details see: http://wiki.apache.org/hadoop/ConnectionRefused

All my services are running porperly and only one node configured, so I don't think the connection is in failure status.

How can I get this issue fixed?

[#2]

@JUNXIONG I have moved this post to the HDFS discussion board since this is an HDFS specific issue.  Hopefully someone in here can assist you.

Regards

[#3 · Accepted solution]

Your edit log transactions are missing in the namenode metadata directory....

"We expected txid 8364, but got txid 27381" ---this mean the edit logs/transactions from 8364 to 27381 are missing....If you don't want to loose the data restore the edit logs from back up metadata if you have or just point the namenode to txid 27381, you may loose data if you point namenode to txid 27381.

[#4]

Thank you Manikumar, I think I can understand what issue is now. So how that issue happen? What's the common causes of it?

[#5]

I think this happens when you try to format the namenode....

[#6]

Would someone be kind enough to describe the process of "just point the namenode to txid 27381"? I've been having this issue on a fresh HDFS cluster, and this sounds like an easy way to fix it.

[#7]

Hi Mythobeast, 

Do you have the procedure to resolve this issue?

[#8]

How to point namenode particular txid ? 

[#9]

Hi, I have the same error, " we expected   txid xxxx , but got yyyy"

How do I change the pointer of the namenode? 

Please advice. 

Thanks