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From "Hiram Chirino (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (APLO-176) What do "Detected store change" messages mean?
Date Wed, 28 Mar 2012 14:37:27 GMT

    [ https://issues.apache.org/jira/browse/APLO-176?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13240450#comment-13240450
] 

Hiram Chirino commented on APLO-176:
------------------------------------

No, those are NOT really harmless. The in memory queue swaps blocks of messages out to disk
but keeps track of the number of messages and bytes in that are contained in the block.  At
a later time when the a message from the block is needed, the block is loaded back up from
the store and we compare the number of messages and bytes that we were able to load from the
store to the expected size of the block.  If there is a difference the queue adjust it's internal
counters to account to the change.  Why, does it do this?  This was put in place so that a
queue could tolerate if a 3rd party changed the message store directly (For example purged
a store of all the messages in a queue).  Is this normal in your case?  No.  I would NOT expect
the LevelDB store and BDB stores to be inconsistent since they don't support external management.

Now that hard part.. Whats the easiest way I can reproduce this?  What kind of messaging scenarios
is this running?  Do all your brokers do this?  
                
> What do "Detected store change" messages mean?
> ----------------------------------------------
>
>                 Key: APLO-176
>                 URL: https://issues.apache.org/jira/browse/APLO-176
>             Project: ActiveMQ Apollo
>          Issue Type: Question
>         Environment: apollo-99-trunk-20120306.040517-2
>            Reporter: Lionel Cons
>
> On one of our brokers, we detected the following messages:
> 2012-03-27 17:17:33,678 | INFO  | Detected store change in range 622852159 to 622862157.
3869 message(s) and 617003 bytes | org.apache.activemq.apollo.broker.QueueEntry | hawtdispatch-DEFAULT-2
> 2012-03-27 17:18:26,337 | INFO  | Detected store change in range 623647284 to 623657282.
6355 message(s) and 947641 bytes | org.apache.activemq.apollo.broker.QueueEntry | hawtdispatch-DEFAULT-2
> 2012-03-27 17:19:41,528 | INFO  | Detected store change in range 624785258 to 624788515.
62 message(s) and 8246 bytes | org.apache.activemq.apollo.broker.QueueEntry | hawtdispatch-DEFAULT-5
> 2012-03-27 17:19:57,644 | INFO  | Detected store change in range 625016042 to 625022112.
62 message(s) and 8246 bytes | org.apache.activemq.apollo.broker.QueueEntry | hawtdispatch-DEFAULT-2
> 2012-03-27 17:19:58,280 | INFO  | Detected store change in range 625016863 to 625026923.
-62 message(s) and -8246 bytes | org.apache.activemq.apollo.broker.QueueEntry | hawtdispatch-DEFAULT-1
> 2012-03-27 17:21:05,636 | INFO  | Detected store change in range 626032257 to 626042255.
6543 message(s) and 1075071 bytes | org.apache.activemq.apollo.broker.QueueEntry | hawtdispatch-DEFAULT-3
> [...]
> Since they are marked as INFO I hope they are harmless (please confirm) but I would anyway
like to understand what they mean and why they are logged.

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