Alan Protasio created AMQ-7132:
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Summary: ActiveMQ reads lots of index pages upon startup (after a
graceful or un graceful shutdown)
Key: AMQ-7132
URL: https://issues.apache.org/jira/browse/AMQ-7132
Project: ActiveMQ
Issue Type: Test
Components: KahaDB
Affects Versions: 5.15.8
Reporter: Alan Protasio
Fix For: 5.16.0, 5.15.9
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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