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From "Steve Loughran (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-13028) add low level counter metrics for S3A; use in read performance tests
Date Wed, 04 May 2016 17:01:13 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-13028?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15270986#comment-15270986
] 

Steve Loughran commented on HADOOP-13028:
-----------------------------------------

1. fixed

3. counting backwards seeks I'm just ignoring that value for now. left it in in case we ever
wanted to start tracking these things. One interesting question about all seek + read stats,
is really histograms of requests would be the best metric; not just the aggregates.

2. let me review that code. In fact, maybe I should factor it out for some independent checks.
Really, we should be asking for the whole thing, shouldn't we? Because even irrespective of
the amount you want in the current read() call, you don't want to have to re-open just because
you didn't know the initial amount, do you? 

I think the http content-range call does require you to specify a limit, so file-len is always
required, but that can be enough



> add low level counter metrics for S3A; use in read performance tests
> --------------------------------------------------------------------
>
>                 Key: HADOOP-13028
>                 URL: https://issues.apache.org/jira/browse/HADOOP-13028
>             Project: Hadoop Common
>          Issue Type: Sub-task
>          Components: fs/s3, metrics
>    Affects Versions: 2.8.0
>            Reporter: Steve Loughran
>            Assignee: Steve Loughran
>         Attachments: HADOOP-13028-001.patch, HADOOP-13028-002.patch, HADOOP-13028-004.patch,
HADOOP-13028-005.patch, HADOOP-13028-006.patch, HADOOP-13028-007.patch, HADOOP-13028-008.patch,
HADOOP-13028-branch-2-008.patch, org.apache.hadoop.fs.s3a.scale.TestS3AInputStreamPerformance-output.txt,
org.apache.hadoop.fs.s3a.scale.TestS3AInputStreamPerformance-output.txt
>
>
> against S3 (and other object stores), opening connections can be expensive, closing connections
may be expensive (a sign of a regression). 
> S3A FS and individual input streams should have counters of the # of open/close/failure+reconnect
operations, timers of how long things take. This can be used downstream to measure efficiency
of the code (how often connections are being made), connection reliability, etc.



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