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https://issues.apache.org/jira/browse/HADOOP-5713?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12716157#action_12716157
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Todd Lipcon commented on HADOOP-5713:
-------------------------------------
Just wanted to drop a note to say that we've seen this problem in practice on a
reasonable size (multirack) cluster as well. We're working on getting some
better data to correlate the log messages with datanode failure events, but as
far as we can tell the symptoms look identical.
Dhruba/Raghu: At this point I am relatively unfamiliar with this part of the
code, but if you guys have a good idea of how to solve this, I'm happy to dive
in and try to produce a patch in the next couple of weeks based on your
guidance. Let me know.
> File write fails after data node goes down
> ------------------------------------------
>
> Key: HADOOP-5713
> URL: https://issues.apache.org/jira/browse/HADOOP-5713
> Project: Hadoop Core
> Issue Type: Bug
> Components: dfs
> Reporter: Alban Chevignard
> Attachments: failed_write.patch
>
>
> If a data node goes down while a file is being written do HDFS, the write
> fails with the following errors:
> {noformat}
> 09/04/20 17:15:39 INFO dfs.DFSClient: Exception in createBlockOutputStream
> java.io.IOException:
> Bad connect ack with firstBadLink 192.168.0.66:50010
> 09/04/20 17:15:39 INFO dfs.DFSClient: Abandoning block
> blk_-6792221430152215651_1003
> 09/04/20 17:15:45 INFO dfs.DFSClient: Exception in createBlockOutputStream
> java.io.IOException:
> Bad connect ack with firstBadLink 192.168.0.66:50010
> 09/04/20 17:15:45 INFO dfs.DFSClient: Abandoning block
> blk_-1056044503329698571_1003
> 09/04/20 17:15:51 INFO dfs.DFSClient: Exception in createBlockOutputStream
> java.io.IOException:
> Bad connect ack with firstBadLink 192.168.0.66:50010
> 09/04/20 17:15:51 INFO dfs.DFSClient: Abandoning block
> blk_-1144491637577072681_1003
> 09/04/20 17:15:57 INFO dfs.DFSClient: Exception in createBlockOutputStream
> java.io.IOException:
> Bad connect ack with firstBadLink 192.168.0.66:50010
> 09/04/20 17:15:57 INFO dfs.DFSClient: Abandoning block
> blk_6574618270268421892_1003
> 09/04/20 17:16:03 WARN dfs.DFSClient: DataStreamer Exception:
> java.io.IOException:
> Unable to create new block.
> at
> org.apache.hadoop.dfs.DFSClient$DFSOutputStream.nextBlockOutputStream(DFSClient.java:2387)
> at
> org.apache.hadoop.dfs.DFSClient$DFSOutputStream.access$1800(DFSClient.java:1746)
> at
> org.apache.hadoop.dfs.DFSClient$DFSOutputStream$DataStreamer.run(DFSClient.java:1924)
> 09/04/20 17:16:03 WARN dfs.DFSClient: Error Recovery for block
> blk_6574618270268421892_1003 bad datanode[1]
> {noformat}
> The tests were done with the following configuration:
> * Hadoop version 0.18.3
> * 3 data nodes with replication count of 2
> * 1 GB file write
> * 1 data node taken down during write
> This issue seems to be caused by the fact that there is a delay between the
> time a data node goes down and the time it is marked as dead by the name
> node. This delay is unavoidable, but the name node should not keep allocating
> new blocks to data nodes that are known to be down by the client. Even by
> adjusting {{heartbeat.recheck.interval}}, there is still a window during
> which this issue can occur.
> One possible fix would be to allow clients to exclude known bad data nodes
> when allocating new blocks. See {{failed_write.patch}} for an example.
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