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From "Han Xiao (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HDFS-3908) In HA mode, when there is a ledger in BK, which is generated after the last checkpoint, missing, NN can't recover it.
Date Mon, 10 Sep 2012 10:45:07 GMT
Han Xiao created HDFS-3908:
------------------------------

             Summary: In HA mode, when there is a ledger in BK, which is generated after the
last checkpoint, missing, NN can't recover it.
                 Key: HDFS-3908
                 URL: https://issues.apache.org/jira/browse/HDFS-3908
             Project: Hadoop HDFS
          Issue Type: Bug
          Components: name-node
    Affects Versions: 2.0.1-alpha
            Reporter: Han Xiao


If not HA, when the num of edits.dir is larger than 1. Missing of one editlog file in a dir
will not relust problem cause of the replica in the other dir. 
However, when in HA mode(using BK as ShareStorage), if an ledger missing, the missing ledger
will not restored at the phase of NN starting even if the related editlog file existing in
local dir.
The missing maintains when NN is still in standby state. However, when the NN enters active
state, it will read the editlog file(related to the missing ledger) in local. But, unfortunately,
the ledger after the missing one in BK can't be readed at such a phase(cause of gap).
Therefore in the following situation, editlogs will not be restored even there is an editlog
file either in BK or in local dir: 

In such a stituation, editlog can't be restored:
1、fsiamge file:fsimage_0000000000000005946.md5
2、legder in zk:
	[zk: localhost:2181(CONNECTED) 0] ls /hdfsEdit/ledgers/edits_00000000000000594
	edits_000000000000005941_000000000000005942
	edits_000000000000005943_000000000000005944
	edits_000000000000005945_000000000000005946
	edits_000000000000005949_000000000000005949   
	(missing edits_000000000000005947_000000000000005948)
3、editlog in local editlog dir:
	-rw-r--r-- 1 root root      30 Sep  8 03:24 edits_0000000000000005947-0000000000000005948
	-rw-r--r-- 1 root root 1048576 Sep  8 03:35 edits_0000000000000005950-0000000000000005950
	-rw-r--r-- 1 root root 1048576 Sep  8 04:42 edits_0000000000000005951-0000000000000005951
	(miss edits_0000000000000005949-0000000000000005919)
4、and the seen_txid
	vm2:/tmp/hadoop-root/dfs/name/current # cat seen_txid
	5949

Here, we want to restored editlog from txid 5946(image) to txid 5949(seen_txid). The 5947-5948
is missing in BK, 5949-5949 is missing in local dir.
When start the NN, the following exception is thrown:

2012-09-08 06:26:10,031 FATAL org.apache.hadoop.hdfs.server.namenode.NameNode: Error encountered
requiring NN shutdown. Shutting down immediately.
java.io.IOException: There appears to be a gap in the edit log.  We expected txid 5949, but
got txid 5950.
        at org.apache.hadoop.hdfs.server.namenode.MetaRecoveryContext.editLogLoaderPrompt(MetaRecoveryContext.java:94)
        at org.apache.hadoop.hdfs.server.namenode.FSEditLogLoader.loadEditRecords(FSEditLogLoader.java:163)
        at org.apache.hadoop.hdfs.server.namenode.FSEditLogLoader.loadFSEdits(FSEditLogLoader.java:93)
        at org.apache.hadoop.hdfs.server.namenode.FSImage.loadEdits(FSImage.java:692)
        at org.apache.hadoop.hdfs.server.namenode.ha.EditLogTailer.doTailEdits(EditLogTailer.java:223)
        at org.apache.hadoop.hdfs.server.namenode.ha.EditLogTailer.catchupDuringFailover(EditLogTailer.java:182)
        at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.startActiveServices(FSNamesystem.java:599)
        at org.apache.hadoop.hdfs.server.namenode.NameNode$NameNodeHAContext.startActiveServices(NameNode.java:1325)
        at org.apache.hadoop.hdfs.server.namenode.ha.ActiveState.enterState(ActiveState.java:61)
        at org.apache.hadoop.hdfs.server.namenode.ha.HAState.setStateInternal(HAState.java:63)
        at org.apache.hadoop.hdfs.server.namenode.ha.StandbyState.setState(StandbyState.java:49)
        at org.apache.hadoop.hdfs.server.namenode.NameNode.transitionToActive(NameNode.java:1233)
        at org.apache.hadoop.hdfs.server.namenode.NameNodeRpcServer.transitionToActive(NameNodeRpcServer.java:990)
        at org.apache.hadoop.ha.protocolPB.HAServiceProtocolServerSideTranslatorPB.transitionToActive(HAServiceProtocolServerSideTranslatorPB.java:107)
        at org.apache.hadoop.ha.proto.HAServiceProtocolProtos$HAServiceProtocolService$2.callBlockingMethod(HAServiceProtocolProtos.java:3633)
        at org.apache.hadoop.ipc.ProtobufRpcEngine$Server$ProtoBufRpcInvoker.call(ProtobufRpcEngine.java:427)
        at org.apache.hadoop.ipc.RPC$Server.call(RPC.java:924)
        at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:1692)
        at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:1688)
        at java.security.AccessController.doPrivileged(Native Method)
        at javax.security.auth.Subject.doAs(Subject.java:396)
        at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1232)
        at org.apache.hadoop.ipc.Server$Handler.run(Server.java:1686)
2012-09-08 06:26:10,036 INFO org.apache.hadoop.hdfs.server.namenode.NameNode: SHUTDOWN_MSG:
/************************************************************
SHUTDOWN_MSG: Shutting down NameNode at vm2/160.161.0.155
************************************************************/

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