[jira] [Commented] (AMQ-5748) Add the ability to get Message Size from a Message Store

["Christopher L. Shannon (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/AMQ-5748?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14521682#comment-14521682 ] 

Christopher L. Shannon commented on AMQ-5748:
---------------------------------------------

I updated my pull request so that the index is not rebuilt automatically.  Instead if the size value does not exist, it will just be 0 unless the index is rebuilt (such as by deleting the index files).  I also added the new metric to the {{DestinationViewMBean}} class, but it probably needs some tests run to make sure it works.  

Besides flow control, another thing I was thinking about adding after this ticket is done is to get even more fine grained and be able to track the store size per Subscription as well as Destination.  It could be implemented in a similar way but I will look at that more closely after this ticket is done.

Let me know what you think.

> Add the ability to get Message Size from a Message Store
> --------------------------------------------------------
>
>                 Key: AMQ-5748
>                 URL: https://issues.apache.org/jira/browse/AMQ-5748
>             Project: ActiveMQ
>          Issue Type: New Feature
>          Components: Broker
>    Affects Versions: 5.11.1
>            Reporter: Christopher L. Shannon
>            Priority: Minor
>
> Currently, the {{MessageStore}} interface supports getting a count for messages ready to deliver using the {{getMessageCount}} method.  It would also be very useful to be able to retrieve the message sizes for those counts as well for keeping track of metrics.
> I've created a pull request to address this that adds a {{getMessageSize}} method that focuses specifically on KahaDB and the Memory store.  The KahaDB store uses the same strategy as the existing {{getMessageCount}} method, which is to iterate over the index and total up the size of the messages.  There are unit tests to show the size calculation and a unit test that shows a store based on version 5 working with the new version (the index is rebuilt)
> One extra issue is that the size was not being serialized to the index (it was not included in the marshaller) so that required making a slight change and adding a new marshaller for {{Location}} to store the size in the location index of the store.  Without this change, the size computation would not work when the broker was restarted since the size was not serialized.
> Note that I wasn't sure the best way to handle the new marshaller and version compatibilities so I incremented the KahaDB version from 5 to 6. If an old version of the index is loaded, the index should be detected as corrupted and be rebuilt with the new format.  If there is a better way to handle this upgrade let me know and the patch can certainly be updated.



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