[jira] [Commented] (OAK-7259) Improve SegmentNodeStoreStats to include number of commits per thread and threads currently waiting on the semaphore

["Michael Dürig (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/OAK-7259?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16381732#comment-16381732 ] 

Michael Dürig commented on OAK-7259:
------------------------------------

[~dulceanu], I like the new patch! It addresses all my concerns. IMO it's fit for trunk. 

Re. {{OpenDataException}}: An empty table is nothing exceptional, that's why I think it is wrong to throw an exception in this case. If there is no way to return an empty table, can we return an explicitly empty table (i.e. just a single row containing dashes or so)? Or would this just make matters worse?

Somewhat related, it might be better to return the raw data from {{CommitsTracker}} and do the conversion to {{TabularData}} to the MBean implementation. This would also simplify testability of {{CommitsTracker}}. 

Also we should probably make {{SegmentNodeStoreStats.setCollectStackTraces}} a property as this makes it easier to use in most JMX clients. 

Finally in the case when collecting stack traces is turned off, AFIU the map of queued writers will contain the thread's name both as key and value. Wouldn't it be clearer to just put "NA" as values? 

> Improve SegmentNodeStoreStats to include number of commits per thread and threads currently waiting on the semaphore
> --------------------------------------------------------------------------------------------------------------------
>
>                 Key: OAK-7259
>                 URL: https://issues.apache.org/jira/browse/OAK-7259
>             Project: Jackrabbit Oak
>          Issue Type: Improvement
>          Components: segment-tar
>            Reporter: Andrei Dulceanu
>            Assignee: Andrei Dulceanu
>            Priority: Major
>              Labels: tooling
>             Fix For: 1.9.0, 1.10
>
>
> When investigating the performance of  {{segment-tar}}, the source of the writes (commits) is a very useful indicator of the cause.
> To better understand which threads are currently writing in the repository and which are blocked on the semaphore, we need to improve {{SegmentNodeStoreStats}} to:
>  * expose the number of commits executed per thread
>  * expose threads currently waiting on the semaphore



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