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https://issues.apache.org/jira/browse/AMQ-7143?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16756319#comment-16756319
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Alan Protasio commented on AMQ-7143:
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Hi [~cshannon]
I will update the tests... On my local SSD i cannot se huge improvement but
when i run in a shared volume (NFS with higher latency) this makes a huge
difference. See the results for a 10MB transaction.
Before:
Running org.apache.activemq.store.kahadb.disk.page.TransactionTest
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 28.774 sec - in
org.apache.activemq.store.kahadb.disk.page.TransactionTest
After:
Running org.apache.activemq.store.kahadb.disk.page.TransactionTest
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 5.834 sec - in
org.apache.activemq.store.kahadb.disk.page.TransactionTest
> Temporary transaction file (PageFile) being opened and closed many times,
> leading poor performance
> --------------------------------------------------------------------------------------------------
>
> Key: AMQ-7143
> URL: https://issues.apache.org/jira/browse/AMQ-7143
> Project: ActiveMQ
> Issue Type: Improvement
> Components: KahaDB
> Affects Versions: 5.15.8
> Reporter: Alan Protasio
> Assignee: Christopher L. Shannon
> Priority: Major
>
> Hi,
> This is an optimization when we have a transaction with many writes (bigger
> than 10mb by default) and activemq creates a temporary transaction file
> (pageFile transaction).
> The problem is when this transaction is committed, this temporary file is
> opened and closed many times (number of writes inside the transaction),
> causing poor performance (this is operation "freezes the world" during the
> checkpoint).
>
> See:
> [https://github.com/apache/activemq/blob/master/activemq-kahadb-store/src/main/java/org/apache/activemq/store/kahadb/disk/page/PageFile.java#L1147]
> [https://github.com/apache/activemq/blob/master/activemq-kahadb-store/src/main/java/org/apache/activemq/store/kahadb/disk/page/PageFile.java#L203]
>
> Note that is the recoveryFile is enabled, we open and close the temporary 3
> times for each index write.
> There is also a small bug that if the transaction is rolledBack, the
> temporary file is left there forever, see:
> [https://github.com/apache/activemq/blob/master/activemq-kahadb-store/src/main/java/org/apache/activemq/store/kahadb/disk/page/Transaction.java#L686]
> [https://github.com/apache/activemq/blob/master/activemq-kahadb-store/src/main/java/org/apache/activemq/store/kahadb/disk/page/PageFile.java#L1200]
>
> As the transaction is rolledback, no writes will be performed and so, the
> file will never be deleted.
> The proposed change, use the same "RandomAccessFile" object used in the
> transaction and close if when all writes is done (so we stop opening and
> closing it for each write, and only do it one time per transaction).
>
> Thanks
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