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https://issues.apache.org/jira/browse/HDFS-14084?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16717986#comment-16717986
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Íñigo Goiri commented on HDFS-14084:
------------------------------------

We should do:
{code}
LOG.debug(" RPC Client stats: {} " + rb.toString());
{code}
Instead of:
{code}
LOG.debug(" RPC Client stats: {}", rb);
{code}

Is there a way to check the output of the logging in the unit test?
It looks like GenericTestUtils has some utils like {{LogCapturer}}.

> Need for more stats in DFSClient
> --------------------------------
>
>                 Key: HDFS-14084
>                 URL: https://issues.apache.org/jira/browse/HDFS-14084
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>    Affects Versions: 3.0.0
>            Reporter: Pranay Singh
>            Assignee: Pranay Singh
>            Priority: Minor
>         Attachments: HDFS-14084.001.patch, HDFS-14084.002.patch, 
> HDFS-14084.003.patch, HDFS-14084.004.patch
>
>
> The usage of HDFS has changed from being used as a map-reduce filesystem, now 
> it's becoming more of like a general purpose filesystem. In most of the cases 
> there are issues with the Namenode so we have metrics to know the workload or 
> stress on Namenode.
> However, there is a need to have more statistics collected for different 
> operations/RPCs in DFSClient to know which RPC operations are taking longer 
> time or to know what is the frequency of the operation.These statistics can 
> be exposed to the users of DFS Client and they can periodically log or do 
> some sort of flow control if the response is slow. This will also help to 
> isolate HDFS issue in a mixed environment where on a node say we have Spark, 
> HBase and Impala running together. We can check the throughput of different 
> operation across client and isolate the problem caused because of noisy 
> neighbor or network congestion or shared JVM.
> We have dealt with several problems from the field for which there is no 
> conclusive evidence as to what caused the problem. If we had metrics or stats 
> in DFSClient we would be better equipped to solve such complex problems.
> List of jiras for reference:
> -------------------------
>  HADOOP-15538 HADOOP-15530 ( client side deadlock)



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