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https://issues.apache.org/jira/browse/HDFS-86?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12900342#action_12900342
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Thanh Do commented on HDFS-86:
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i have a cluster of two nodes. Say a block with 2 replicas, and one of them get
corrupted.
The corrupted block is reported to NN, but it is never deleted or replicated,
even after NN restarts.
Not sure this is a bug or just a policy.
I am playing the append-trunk
> Corrupted blocks get deleted but not replicated
> -----------------------------------------------
>
> Key: HDFS-86
> URL: https://issues.apache.org/jira/browse/HDFS-86
> Project: Hadoop HDFS
> Issue Type: Bug
> Reporter: Hairong Kuang
> Assignee: Hairong Kuang
> Attachments: blockInvalidate.patch
>
>
> When I test the patch to HADOOP-1345 on a two node dfs cluster, I see that
> dfs correctly delete the corrupted replica and successfully retry reading
> from the other correct replica, but the block does not get replicated. The
> block remains with only 1 replica until the next block report comes in.
> In my testcase, since the dfs cluster has only 2 datanodes, the target of
> replication is the same as the target of block invalidation. After poking
> the logs, I found out that the namenode sent the replication request before
> the block invalidation request.
> This is because the namenode does not invalidate a block well. In
> FSNamesystem.invalidateBlock, it first puts the invalidate request in a queue
> and then immediately removes the replica from its state, which triggers the
> choosing a target for the block. When requests are sent back to the target
> datanode as a reply to a heartbeat message, the replication requests have
> higher priority than the invalidate requests.
> This problem could be solved if a namenode removes an invalidated replica
> from its state only after the invalidate request is sent to the datanode.
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