File write fails after data node goes down
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Key: HADOOP-5713
URL: https://issues.apache.org/jira/browse/HADOOP-5713
Project: Hadoop Core
Issue Type: Bug
Components: dfs
Reporter: Alban Chevignard
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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