What is the purpose of the Journal files?

[garymarsh]

I have a very simple program that has two classes, both generate JMS messages and both accept each others messages with onMessage() methods. If I delete all the files that are in my data/journal directory, after startup I find that the program by default generates 400Mgs of journal files (40 files 10Mgs each). These seem to be defined in the jbm-configuration.xml file at about lines 85 to 94, here is the snippit :

<!-- 10 MB journal file size -->
<journal-file-size>10485760</journal-file-size>

<journal-min-files>40</journal-min-files>

<!-- Maximum simultaneous asynchronous writes accepted by the native layer.
(parameter ignored on NIO)
You can verify the max AIO on the OS level at /proc/sys/fs/aio_max_nr. (aio-nr will give you the current max-aio being used)
-->
<journal-max-aio>5000</journal-max-aio>

I a curious, is this really necessary (400 MGs minimum) and what is it used for?

Regards,

GMarsh

[garymarsh]

I see in the JBossMessagingUsersGuide.pdf document that the journal mechanism is what you use for message persistence but for a small program isn't 400 MGs a little bit of over kill? Is it possible to pair this down without braking something?

GMarsh

[timfox]

Yes this is configurable, see the main config file.

[clebert.suconic]

On trunk, the journal-min-files is using 15.


The journal is what stores the persistent-message. If you restart the server, we will recover a lot of stuff from our persistent store (the Journal).