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https://issues.apache.org/jira/browse/HDFS-9909?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15226494#comment-15226494
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Bogdan Raducanu commented on HDFS-9909:
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OK, thanks.
My first idea was to just signal this case through a special exception, e.g.
ReplicaWaitingRecoveryException which is reported to the client app. Then, the
client app can choose what to do. In my case, when I get this exception, I
would call DFSClient.recoverLease to trigger the lease recovery and open again
after this. That's what I do in the write case, before the soft limit expires.
In fact, as a workaround, I do this even for reading now, just now I get a
generic exception. Just an idea. Maybe you find something better.
> Can't read file after hdfs restart
> ----------------------------------
>
> Key: HDFS-9909
> URL: https://issues.apache.org/jira/browse/HDFS-9909
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: hdfs-client, namenode
> Affects Versions: 2.7.1, 2.7.2
> Reporter: Bogdan Raducanu
> Assignee: Xiao Chen
> Priority: Critical
> Attachments: Main.java
>
>
> If HDFS is restarted while a file is open for writing then new clients can't
> read that file until the hard lease limit expires and block recovery starts.
> Scenario:
> 1. write to file, call hflush
> 2. without closing the file, restart hdfs
> 3. after hdfs is back up, opening file for reading from a new client fails
> for 1 hour
> Repro attached.
> Thoughts:
> * possibly this also happens in other cases not just when hdfs is restarted
> (e.g. only all datanodes in pipeline are restarted)
> * As far as I can tell this happens because the last block is RWR and
> getReplicaVisibleLength returns -1 for this. The recovery starts after hard
> lease limit expires (so file is readable only after 1 hour).
> * one can call recoverLease which will start the lease recovery sooner, BUT,
> how can one know when to call this? The exception thrown is IOException which
> can happen for other reasons.
> I think a reasonable solution would be to return a specialized exception
> (similar to AlreadyBeingCreatedException when trying to write to open file).
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