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From "Ming Ma (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HDFS-9579) Provide bytes-read-by-network-distance metrics at FileSystem.Statistics level
Date Fri, 18 Dec 2015 21:49:46 GMT
Ming Ma created HDFS-9579:

             Summary: Provide bytes-read-by-network-distance metrics at FileSystem.Statistics
                 Key: HDFS-9579
                 URL: https://issues.apache.org/jira/browse/HDFS-9579
             Project: Hadoop HDFS
          Issue Type: Improvement
            Reporter: Ming Ma

For cross DC distcp or other applications, it becomes useful to have insight as to the traffic
volume for each network distance to distinguish cross-DC traffic, local-DC-remote-rack, etc.

FileSystem's existing {{bytesRead}} metrics tracks all the bytes read. To provide additional
metrics for each network distance, we can add additional metrics to FileSystem level and have
{{DFSInputStream}} update the value based on the network distance between client and the datanode.

{{DFSClient}} will resolve client machine's network location as part of its initialization.
It doesn't need to resolve datanode's network location for each read as {{DatanodeInfo}} already
has the info.

There are existing HDFS specific metrics such as {{ReadStatistics}} and {{DFSHedgedReadMetrics}}.
But these metrics are only accessible via {{DFSClient}} or {{DFSInputStream}}. Not something
that application framework such as MR and Tez can get to. That is the benefit of storing these
new metrics in FileSystem.Statistics.

This jira only includes metrics generation by HDFS. The consumption of these metrics at MR
and Tez will be tracked by separated jiras.

We can add similar metrics for HDFS write scenario later if it is necessary.

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