[jira] Commented: (HADOOP-3124) DFS data node should not use hard coded 10 minutes as write timeout.

["Raghu Angadi (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HADOOP-3124?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12583206#action_12583206 ] 

Raghu Angadi commented on HADOOP-3124:
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> 3. Different datanodes in a pipeline should use different timeout values for writing to the downstream.

This is already the case : timeout is : 10 min + 5sec * (number of datanodes - position in the pipeline). Client's postion is 0, first datanode's position is 1 etc.

+1 for making this a config.

Note that there was no timeout for this before 0.17, it client would get stuck forever. 10 min was added as a very conservative value. What should be the default?

Though not relevant here, probably we need different write timeouts while receiving a block and while sending a block.

I am curious to know if you have any info on why one of the datanode's was not able to read for 10minutes.

> DFS data node should not use hard coded 10 minutes as write timeout.
> --------------------------------------------------------------------
>
>                 Key: HADOOP-3124
>                 URL: https://issues.apache.org/jira/browse/HADOOP-3124
>             Project: Hadoop Core
>          Issue Type: Bug
>            Reporter: Runping Qi
>
> This problem happens in 0.17 trunk
> I saw reducers waited 10 minutes for writing data to dfs and got timeout.
> The client retries again and timeouted after another 19 minutes.
> After looking into the code, it seems that the dfs data node uses 10 minutes as timeout for wtiting data into the data node pipeline.
> I thing we have three issues:
> 1. The 10 minutes timeout value is too big for writing a chunk of data (64K) through the data node pipeline.
> 2. The timeout value should not be hard coded.
> 3. Different datanodes in a pipeline should use different timeout values for writing to the downstream.
> A reasonable one maybe (20 secs * numOfDataNodesInTheDownStreamPipe).
> For example, if the replication factor is 3, the client uses 60 secs, the first data node use 40 secs, the second datanode use 20secs.

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