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https://issues.apache.org/jira/browse/HBASE-7715?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13566167#comment-13566167
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Andrew Wang commented on HBASE-7715:
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Cool patch, Ted!
There's also one more usage of setSafeMode in FSUtils#checkDfsSafeMode that
should probably be fixed. Uma's comment about using #isInSafeMode() is also
probably a bit cleaner.
I don't think that the StandbyException is actually propagated up this high, it
gets caught and used in the failover logic in DFSClient. You can check me on
that one though.
I'd also prefer to see an explicit catch of the {{NoSuchMethod}} exception (and
a comment denoting why we're doing all this this business), rather than a
generic {{Exception}} catch. Then you can avoid rethrowing in the catch.
> FSUtils#waitOnSafeMode can incorrectly loop on standby NN
> ---------------------------------------------------------
>
> Key: HBASE-7715
> URL: https://issues.apache.org/jira/browse/HBASE-7715
> Project: HBase
> Issue Type: Bug
> Affects Versions: 0.94.4
> Reporter: Andrew Wang
> Assignee: Ted Yu
> Fix For: 0.96.0
>
> Attachments: 7715-trunk-v2.txt
>
>
> We encountered an issue where HMaster failed to start with an active NN not
> in safe mode and a standby NN in safemode. The relevant lines in
> {{FSUtils.java}} show the issue:
> {noformat}
> while
> (dfs.setSafeMode(org.apache.hadoop.hdfs.protocol.FSConstants.SafeModeAction.SAFEMODE_GET))
> {
> {noformat}
> This call skips the normal client failover from the standby to active NN, so
> it will loop polling the standby NN if it unfortunately talks to the standby
> first.
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