[jira] Commented: (HADOOP-1297) datanode sending block reports to namenode once every second

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

    [ https://issues.apache.org/jira/browse/HADOOP-1297?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12491797 ] 

Raghu Angadi commented on HADOOP-1297:
--------------------------------------

+1.

Couple of minor things:
 # {{invalidBlks[i] + "file "}} neess a space before 'file' 
 # You might want to include comment saying extra checks like {{f.exists()}} and exceptions are temporary.


> datanode sending block reports to namenode once every second
> ------------------------------------------------------------
>
>                 Key: HADOOP-1297
>                 URL: https://issues.apache.org/jira/browse/HADOOP-1297
>             Project: Hadoop
>          Issue Type: Bug
>          Components: dfs
>            Reporter: dhruba borthakur
>         Assigned To: dhruba borthakur
>         Attachments: datanodeDeleteBlocks.patch
>
>
> The namenode is requesting a block to be deleted. The datanode tries this operation and encounters an error because the block is not in the blockMap. The processCommand() method raises an exception. The code is such that the variable lastBlockReport is not set if processCommand() raises an exception. This means that the datanode immediately send another block report to the namenode. The eats up quite a bit of CPU on namenode.
> In short, the above condition causes the datanode to send blockReports almost once every second!
> I propose that we do the following:
> 1. in Datanode.offerService, replace the following piece of code
> DatanodeCommand cmd = namenode.blockReport(dnRegistration,
> data.getBlockReport());
> processCommand(cmd);
> lastBlockReport = now;
> with
> DatanodeCommand cmd = namenode.blockReport(dnRegistration,
> data.getBlockReport());
> lastBlockReport = now;
> processCommand(cmd);
> 2. In FSDataSet.invalidate:
> a) continue to process all blocks in invalidBlks[] even if one in the middle encounters a problem.
> b) if getFile() returns null, still invoke volumeMap.get() and print whether we found the block in
> volumes or not. The volumeMap is used to generate the blockReport and this might help in debugging.
> [

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