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From "Jing Zhao (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-10659) Namenode crashes after Journalnode re-installation in an HA cluster due to missing paxos directory
Date Thu, 21 Jul 2016 17:44:21 GMT

    [ https://issues.apache.org/jira/browse/HDFS-10659?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15388104#comment-15388104

Jing Zhao commented on HDFS-10659:

Yeah I checked the code again and I think you're right. The format step only happens in {{namenode
-initializeSharedEdits}} or {{namenode -format}}. We should let JN create directories if the
storage root directory is empty.

> Namenode crashes after Journalnode re-installation in an HA cluster due to missing paxos
> --------------------------------------------------------------------------------------------------
>                 Key: HDFS-10659
>                 URL: https://issues.apache.org/jira/browse/HDFS-10659
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: ha, journal-node
>    Affects Versions: 2.7.1
>            Reporter: Amit Anand
> In my environment I am seeing {{Namenodes}} crashing down after majority of {{Journalnodes}}
are re-installed. We manage multiple clusters and do rolling upgrades followed by rolling
re-install of each node including master(NN, JN, RM, ZK) nodes. When a journal node is re-installed
or moved to a new disk/host, instead of running {{"initializeSharedEdits"}} command, I copy
{{VERSION}} file from one of the other {{Journalnode}} and that allows my {{NN}} to start
writing data to the newly installed {{Journalnode}}.
> To acheive quorum for JN and recover unfinalized segments NN during starupt creates NNNN.tmp
files under {{"<disk>/jn/current/paxos"}} directory . In current implementation "paxos"
directry is only created during {{"initializeSharedEdits"}} command and if a JN is re-installed
the "paxos" directory is not created upon JN startup or by NN while writing NNNN.tmp files
which causes NN to crash with following error message:
> {code}
> /disk/1/dfs/jn/Test-Laptop/current/paxos/64044.tmp (No such file
or directory)
>         at java.io.FileOutputStream.open(Native Method)
>         at java.io.FileOutputStream.<init>(FileOutputStream.java:221)
>         at java.io.FileOutputStream.<init>(FileOutputStream.java:171)
>         at org.apache.hadoop.hdfs.util.AtomicFileOutputStream.<init>(AtomicFileOutputStream.java:58)
>         at org.apache.hadoop.hdfs.qjournal.server.Journal.persistPaxosData(Journal.java:971)
>         at org.apache.hadoop.hdfs.qjournal.server.Journal.acceptRecovery(Journal.java:846)
>         at org.apache.hadoop.hdfs.qjournal.server.JournalNodeRpcServer.acceptRecovery(JournalNodeRpcServer.java:205)
>         at org.apache.hadoop.hdfs.qjournal.protocolPB.QJournalProtocolServerSideTranslatorPB.acceptRecovery(QJournalProtocolServerSideTranslatorPB.java:249)
>         at org.apache.hadoop.hdfs.qjournal.protocol.QJournalProtocolProtos$QJournalProtocolService$2.callBlockingMethod(QJournalProtocolProtos.java:25435)
>         at org.apache.hadoop.ipc.ProtobufRpcEngine$Server$ProtoBufRpcInvoker.call(ProtobufRpcEngine.java:616)
>         at org.apache.hadoop.ipc.RPC$Server.call(RPC.java:969)
>         at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:2151)
>         at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:2147)
>         at java.security.AccessController.doPrivileged(Native Method)
>         at javax.security.auth.Subject.doAs(Subject.java:415)
>         at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1657)
>         at org.apache.hadoop.ipc.Server$Handler.run(Server.java:2145)
> {code}
> The current [getPaxosFile|https://github.com/apache/hadoop/blob/trunk/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/qjournal/server/JNStorage.java#L128-L130]
method simply returns a path to a file under "paxos" directory without verifiying its existence.
Since "paxos" directoy holds files that are required for NN recovery and acheiving JN quorum
my proposed solution is to add a check to "getPaxosFile" method and create the {{"paxos"}}
directory if it is missing.

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