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https://issues.apache.org/jira/browse/AMQ-6099?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15067515#comment-15067515
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Tim Bain commented on AMQ-6099:
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Also, I'm not convinced you'd ever have more than 2 versions at once; you'd
have to have messages that were stuck in the store for longer than the lifetime
of a particular version, and only when the from version, intermediate version,
and to version all used different versions of OpenWire. I guess it's possible,
but it doesn't seem very likely.
Either way, though, once you can handle two versions, is the code to support
three actually that complicated? Is there even any code at all, once you have
support for two versions?
> Allow broker to read any OpenWire version from KahaDB
> -----------------------------------------------------
>
> Key: AMQ-6099
> URL: https://issues.apache.org/jira/browse/AMQ-6099
> Project: ActiveMQ
> Issue Type: New Feature
> Components: KahaDB
> Affects Versions: 5.x
> Reporter: Tim Bain
>
> The current KahaDB implementation only allows a single OpenWire version to be
> read from the store. This works fine during normal operations, but when a
> user upgrades to a version of ActiveMQ that uses a different OpenWire
> version, the new broker is unable to read any persisted messages from the
> store because of the version mismatch, as described in AMQ-5995.
> Broker upgrades are going to happen, and the requirement that they be done
> with an empty message store, or that the user apply temporary workarounds
> like running the old broker in a networked configuration that's not the
> standard config for the cluster, leads to a less-than-satisfactory experience
> during the upgrade. As much as possible, broker upgrades should be seamless;
> sometimes that's not possible, but in this case it seems like code that would
> be able to read any version of OpenWire but only write the current one (and
> that could be less-efficient with older versions if necessary) wouldn't be
> all that hard and would eliminate this problem.
> Alternatively, we could create a command-line utility to transform a set of
> KahaDB data files from an (offline) broker from one version to another.
> That's a little clunkier for the user, but reasonable if it's substantially
> easier to implement.
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