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https://issues.apache.org/jira/browse/HDFS-7704?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14305452#comment-14305452
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Charles Lamb commented on HDFS-7704:
------------------------------------

Hi [~shahrs87],

I only have a few nits on the latest rev:

BPServiceActor.java:

Line continuations are 4 spaces.

At line 257 you've introduced a line containing spaces. Also, you've removed 
the last newline of the file.

BPServiceActorAction.java:

Line continuations are 4 spaces (statements in a new block are indented 2 
spaces).

ErrorReportAction.java:

s/A ErrorReportAction/An ErrorReportAction/
Can LOG be private?

ReportBadBlockAction.java

Can LOG be private?

s/to namenode :/to namenode: /
The block comment in that catch should be:

/*
 * One common reason ...
 */


> DN heartbeat to Active NN may be blocked and expire if connection to Standby 
> NN continues to time out. 
> -------------------------------------------------------------------------------------------------------
>
>                 Key: HDFS-7704
>                 URL: https://issues.apache.org/jira/browse/HDFS-7704
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: datanode, namenode
>    Affects Versions: 2.5.0
>            Reporter: Rushabh S Shah
>            Assignee: Rushabh S Shah
>         Attachments: HDFS-7704-v2.patch, HDFS-7704-v3.patch, 
> HDFS-7704-v4.patch, HDFS-7704.patch
>
>
> There are couple of synchronous calls in BPOfferservice (i.e reportBadBlocks 
> and trySendErrorReport) which will wait for both of the actor threads to 
> process this calls.
> This calls are made with writeLock acquired.
> When reportBadBlocks() is blocked at the RPC layer due to unreachable NN, 
> subsequent heartbeat response processing has to wait for the write lock. It 
> eventually gets through, but takes too long and it blocks the next heartbeat.
> In our HA cluster setup, the standby namenode was taking a long time to 
> process the request.
> Requesting improvement in datanode to make the above calls asynchronous since 
> these reports don't have any specific
> deadlines, so extra few seconds of delay should be acceptable.



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