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https://issues.apache.org/jira/browse/HDFS-9579?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15170428#comment-15170428
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Mingliang Liu commented on HDFS-9579:
-------------------------------------
The latest patch looks pretty good to me overall. Nice work. Thanks for
reporting and working on this, [~mingma].
+1 (non-binding) after the following comments are addressed/considered.
1. {{DFSClient#stats}} is package local mainly because it's used in
{{DFSInputStream}} for updating the read bytes counter. I'm wondering if we can
delegate the {{updateFileSystemReadStats}} logic to {{DFSClient}}. This way the
{{stats}} is confined in {{DFSClient}} and thus transparent to
{{DFSInputStream}}.
2. As the erasure coding merged in {{trunk}} branch, we have to maintain the
{{DFSStripeInputStream}} along with {{DFSInputStream}}. In this case, we need
update {{DFSStripeInputStream#readWithStrategy}} as well, I suppose?
3. Nit for reducing failing message confusion:
{code:java}
- assertEquals(cluster.getDistance(node1, node2), 0);
+ assertEquals(0, cluster.getDistance(node1, node2));
{code}
See
[http://junit.org/javadoc/latest/org/junit/Assert.html#assertEquals(java.lang.Object,
java.lang.Object)]
> Provide bytes-read-by-network-distance metrics at FileSystem.Statistics level
> -----------------------------------------------------------------------------
>
> Key: HDFS-9579
> URL: https://issues.apache.org/jira/browse/HDFS-9579
> Project: Hadoop HDFS
> Issue Type: Improvement
> Reporter: Ming Ma
> Assignee: Ming Ma
> Attachments: HDFS-9579-2.patch, HDFS-9579-3.patch, HDFS-9579-4.patch,
> HDFS-9579-5.patch, HDFS-9579-6.patch, HDFS-9579.patch, MR job counters.png
>
>
> 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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