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https://issues.apache.org/jira/browse/AMQ-6099?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15068300#comment-15068300
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Christopher L. Shannon commented on AMQ-6099:
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Good points, [~tabish121]. The second one is especially tricky. I could also
see a scenario where messages are read by the wrong marshaller and there's no
error because the bytes happen to line up, but they are read into the wrong
fields. The more I think about it the more ways I could see this going badly
if trying to unmarshall something with the wrong marshaller version and not
being able to properly handle it.
> 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.
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