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https://issues.apache.org/jira/browse/HADOOP-13028?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15274739#comment-15274739
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Chris Nauroth commented on HADOOP-13028:
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bq. {{S3AInputStream#closed}}: it seems like this should be an
{{AtomicBoolean}}. Otherwise two threads could both enter this code block,
right?
I think this is OK. The whole {{close}} method is {{synchronized}}, so we
won't have two threads concurrently doing the actual close. Almost all other
accesses of {{closed}} are within {{synchronized}} methods too. It's marked
{{volatile}} to help with one unsynchronized access from {{readFully}}, calling
into {{checkNotClosed}}. That's only a read, not an update, so {{volatile}} is
sufficient.
I don't object to using {{AtomicBoolean}}, but I don't think it's necessary.
bq. Is it really necessary to put statistics information into the toString
methods of the streams?
I'd like to keep this. It's very convenient for logging.
{{TestS3AInputStreamPerformance}} uses it for both logging output and detailed
assertion messages. It's poor practice to rely on a Java object's {{toString}}
output as a stable, parseable format. This is something that I'd like to see
clarified in our compatibility documentation.
I don't have a strong opinion on the naming questions.
> 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-13028-009.patch,
> HADOOP-13028-branch-2-008.patch, HADOOP-13028-branch-2-009.patch,
> HADOOP-13028-branch-2-010.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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