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https://issues.apache.org/jira/browse/HDFS-11659?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15997280#comment-15997280
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Lei (Eddy) Xu commented on HDFS-11659:
--------------------------------------
[~yzhangal] The DataNode is added later after hot swap is due to that we'd like
to make sure the write pipeline is one the DataNode at the time that we remove
the volume. If we set 4 nodes at the beginning, it will be 25% chance that it
is not the case.
> TestDataNodeHotSwapVolumes.testRemoveVolumeBeingWritten fail due to no
> DataNode available for pipeline recovery.
> ----------------------------------------------------------------------------------------------------------------
>
> Key: HDFS-11659
> URL: https://issues.apache.org/jira/browse/HDFS-11659
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: datanode
> Affects Versions: 2.7.3, 3.0.0-alpha2
> Reporter: Lei (Eddy) Xu
> Assignee: Lei (Eddy) Xu
> Attachments: HDFS-11659.000.patch
>
>
> The test fails after the following error messages:
> {code}
> java.io.IOException: Failed to replace a bad datanode on the existing
> pipeline due to no more good datanodes being available to try. (Nodes:
> current=[DatanodeInfoWithStorage[127.0.0.1:57377,DS-b4ec61fc-657c-4e2a-9dc3-8d93b7769a2b,DISK],
>
> DatanodeInfoWithStorage[127.0.0.1:47448,DS-18bca8d7-048d-4d7f-9594-d2df16096a3d,DISK]],
>
> original=[DatanodeInfoWithStorage[127.0.0.1:57377,DS-b4ec61fc-657c-4e2a-9dc3-8d93b7769a2b,DISK],
>
> DatanodeInfoWithStorage[127.0.0.1:47448,DS-18bca8d7-048d-4d7f-9594-d2df16096a3d,DISK]]).
> The current failed datanode replacement policy is DEFAULT, and a client may
> configure this via
> 'dfs.client.block.write.replace-datanode-on-failure.policy' in its
> configuration.
> at
> org.apache.hadoop.hdfs.DFSOutputStream$DataStreamer.findNewDatanode(DFSOutputStream.java:1280)
> at
> org.apache.hadoop.hdfs.DFSOutputStream$DataStreamer.addDatanode2ExistingPipeline(DFSOutputStream.java:1354)
> at
> org.apache.hadoop.hdfs.DFSOutputStream$DataStreamer.setupPipelineForAppendOrRecovery(DFSOutputStream.java:1512)
> at
> org.apache.hadoop.hdfs.DFSOutputStream$DataStreamer.processDatanodeError(DFSOutputStream.java:1236)
> at
> org.apache.hadoop.hdfs.DFSOutputStream$DataStreamer.run(DFSOutputStream.java:721)
> {code}
> In such case, the DataNode that has removed can not be used in the pipeline
> recovery.
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