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https://issues.apache.org/jira/browse/HDFS-14806?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16966967#comment-16966967
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Erik Krogen commented on HDFS-14806:
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Hi [~vagarychen] I am +1 on this patch besides the javac and checkstyle
warnings reported in the Jenkins report. Can we make sure they are addressed?
> Bootstrap standby may fail if used in-progress tailing
> ------------------------------------------------------
>
> Key: HDFS-14806
> URL: https://issues.apache.org/jira/browse/HDFS-14806
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: namenode
> Affects Versions: 3.3.0
> Reporter: Chen Liang
> Assignee: Chen Liang
> Priority: Major
> Attachments: HDFS-14806.001.patch, HDFS-14806.002.patch,
> HDFS-14806.003.patch
>
>
> One issue we went across was that if in-progress tailing is enabled,
> bootstrap standby could fail.
> When in-progress tailing is enabled, Bootstrap uses the RPC mechanism to get
> edits. There is a config {{dfs.ha.tail-edits.qjm.rpc.max-txns}} that sets an
> upper bound on how many txnid can be included in one RPC call. The default is
> 5000. Meaning bootstraping NN (say NN1) can only pull at most 5000 edits from
> JN. However, as part of bootstrap, NN1 queries another NN (say NN2) for NN2's
> current transactionID, NN2 may return a state that is > 5000 txnid from NN1's
> current image. But NN1 can only see 5000 more txnid from JNs. At this point
> NN1 goes panic, because txnid retuned by JNs is behind NN2's returned state,
> bootstrap then fail.
> Essentially, bootstrap standby can fail if both of two following conditions
> are met:
> # in-progress tailing is enabled AND
> # the boostraping NN is too far (>5000 txid) behind
> Increasing the value of {{dfs.ha.tail-edits.qjm.rpc.max-txns}} to some super
> large value allowed bootstrap to continue. But this is hardly the ideal
> solution.
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