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https://issues.apache.org/jira/browse/HDFS-14084?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16712046#comment-16712046
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Wei-Chiu Chuang commented on HDFS-14084:
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bq. I'm not sure on the best way to get the information out... logging (trace
leve?) might be too verbose but I don't see many more ways.
IMO logging latency number at trace level (for each op?) doesn't work too well.
For most part I am interested in the distribution of latency number. For
example, 50%-tile,90%-tile,99%-tile, of OP_DELETE, over some period of time,
say the past 30 seconds, 5 minutes.
We already have something similar at RPC server level (via config key
dfs.metrics.percentiles.intervals), just that we don't have that in the client
side.
> 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
>
>
> 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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