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https://issues.apache.org/jira/browse/AMQ-7132?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16742231#comment-16742231
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Alan Protasio edited comment on AMQ-7132 at 1/14/19 3:53 PM:
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Hi [~cshannon], Thanks.
The check you commented there is being done in the StoredDestinationMarshaller:
[https://github.com/apache/activemq/pull/336/commits/eebcdbfe7b1681e6093439ff5be281a585a307c4#diff-e3b8fff8c2133dfd70999705bbb558b3R2580]
If in the future we need to change the MessageStoreStatisticsMarshaller then
we need to add a kahadb version check there. But for now, the check should be
in the StoredDestinationMarshaller, as the difference btw the versions is
whether StoredDestinationMarshaller has or has not this information.
was (Author: alanprot):
Hi [~cshannon], Thanks.
The check you commented there is being done in the StoredDestinationMarshaller:
[https://github.com/apache/activemq/pull/336/commits/eebcdbfe7b1681e6093439ff5be281a585a307c4#diff-e3b8fff8c2133dfd70999705bbb558b3R2580]
If in the future we need to change the MessageStoreStatisticsMarshaller then
we need to add a kahadb version check there. But for now, the check should be
in the StoredDestinationMarshaller, as the difference btw the versions is if
StoredDestinationMarshaller has or has not this information.
> ActiveMQ reads lots of index pages upon startup (after a graceful or
> ungraceful shutdown)
> -----------------------------------------------------------------------------------------
>
> Key: AMQ-7132
> URL: https://issues.apache.org/jira/browse/AMQ-7132
> Project: ActiveMQ
> Issue Type: Improvement
> Components: KahaDB
> Affects Versions: 5.15.8
> Reporter: Alan Protasio
> Assignee: Christopher L. Shannon
> Priority: Major
> Fix For: 5.16.0
>
>
> Hi.
> We noticed that ActiveMQ reads lots of pages in the index file when is
> starting up to recover the destinations statistics:
> [https://github.com/apache/activemq/blob/master/activemq-kahadb-store/src/main/java/org/apache/activemq/store/kahadb/KahaDBStore.java#L819]
> Nowadays, in order to do that, activemq traverse the
> storedDestination.locationIndex to get the messageCount and totalMessageSize
> of each destination. For destinations with lots of messages this process can
> take a while making the startup process take long time.
> In a case of a master-slave broker, this prevent the broker to fast failover
> and does not meet what is stated on
> [http://activemq.apache.org/shared-file-system-master-slave.html.]
> {quote}If you have a SAN or shared file system it can be used to provide
> _high availability_ such that if a broker is killed, another broker can take
> over immediately.
> {quote}
> One solution for this is keep track of the destination statistics summary in
> the index file and doing so, we dont need to read all the locationIndex on
> the start up.
> The code change proposed is backward compatible but need a bump on the kahadb
> version. If this information is not in the index, the broker will fall back
> to the current implementation, which means that the first time people upgrade
> to the new version, it will still have to read the locationIndex, but
> subsequent restarts will be fast.
> This change should have a negligible performance impact during normal
> activemq operation, as this change introduce a few more bytes of data to the
> index and this information will be on checkpoints. Also, this new information
> is synchronized with the locationIndex as they are update at the same
> transaction.
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