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https://issues.apache.org/jira/browse/HDFS-9576?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15095489#comment-15095489
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Colin Patrick McCabe commented on HDFS-9576:
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Cool. This sounds useful for profiling applications.
{code}
scope.addKVAnnotation("position", Long.toString(pos));
{code}
Can we use "pos" instead? It would help keep span sizes down.
Hmm. I'm curious whether we need to separate request length and returned
length, or if we can just have one length, which is the length actually read.
It seems like if you see a lot of really short lengths, you can do some deeper
digging to figure out why... but I'm not sure if it's worth carrying this info
on every read trace span.
> HTrace: collect position/length information on read operations
> --------------------------------------------------------------
>
> Key: HDFS-9576
> URL: https://issues.apache.org/jira/browse/HDFS-9576
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: hdfs-client, tracing
> Affects Versions: 2.7.1
> Reporter: Zhe Zhang
> Assignee: Zhe Zhang
> Attachments: HDFS-9576.00.patch, HDFS-9576.01.patch,
> HDFS-9576.02.patch, HDFS-9576.03.patch, HDFS-9576.04.patch, HDFS-9576.05.patch
>
>
> HTrace currently collects the path of each read operation (both stateful and
> position reads). To better understand applications' I/O behavior, it is also
> useful to track the position and length of read operations.
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