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https://issues.apache.org/jira/browse/HDFS-16601?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18055709#comment-18055709
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ASF GitHub Bot commented on HDFS-16601:
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github-actions[bot] closed pull request #4369: HDFS-16601. DataTransfer should
throw IOException to client
URL: https://github.com/apache/hadoop/pull/4369
> DataTransfer should throw IOException to Client
> -----------------------------------------------
>
> Key: HDFS-16601
> URL: https://issues.apache.org/jira/browse/HDFS-16601
> Project: Hadoop HDFS
> Issue Type: Bug
> Reporter: ZanderXu
> Assignee: ZanderXu
> Priority: Major
> Labels: pull-request-available
> Time Spent: 2h 10m
> Remaining Estimate: 0h
>
> In our production environment, we found a bug and stack like:
> {code:java}
> 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[127.0.0.1:59687,DS-b803febc-7b22-4144-9b39-7bf521cdaa8d,DISK],
>
> DatanodeInfoWithStorage[127.0.0.1:59670,DS-0d652bc2-1784-430d-961f-750f80a290f1,DISK]],
>
> original=[DatanodeInfoWithStorage[127.0.0.1:59670,DS-0d652bc2-1784-430d-961f-750f80a290f1,DISK],
>
> DatanodeInfoWithStorage[127.0.0.1:59687,DS-b803febc-7b22-4144-9b39-7bf521cdaa8d,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.DataStreamer.findNewDatanode(DataStreamer.java:1418)
> at
> org.apache.hadoop.hdfs.DataStreamer.addDatanode2ExistingPipeline(DataStreamer.java:1478)
> at
> org.apache.hadoop.hdfs.DataStreamer.handleDatanodeReplacement(DataStreamer.java:1704)
> at
> org.apache.hadoop.hdfs.DataStreamer.setupPipelineInternal(DataStreamer.java:1605)
> at
> org.apache.hadoop.hdfs.DataStreamer.setupPipelineForAppendOrRecovery(DataStreamer.java:1587)
> at
> org.apache.hadoop.hdfs.DataStreamer.processDatanodeOrExternalError(DataStreamer.java:1371)
> at org.apache.hadoop.hdfs.DataStreamer.run(DataStreamer.java:674)
> {code}
> And the root cause is that DFSClient cannot perceive the exception of
> TransferBlock during PipelineRecovery. If failed during TransferBlock, the
> DFSClient will retry all datanodes in the cluster and then failed.
> When client is recovering pipeline, the source dn selected to transfer block
> to new DN may be abnormal, it cannot successfully transfer the block to the
> new node. But the failed exception not returned to the client, Client also
> thought transfer successfully. But there is not block in the new DN, so
> Client failed to build the pipeline, and marked the new DN is bad. And then
> Client will add the new DN into exclude list to get a new DN for the new loop
> pipeline recovery. The new pipeline recovery will still choose the abnormal
> dn as the source dn to transfer block, and it will fail again..
> So I think that DN should return the failed exception of transfer to Client,
> so that Client can choose anther existed dn as the source dn to transfer the
> block to a new DN.
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