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<p class="MsoNormal">Hi,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I noticed that right now, when we make changes (adding/removing fields) in
<a href="https://github.com/openstack/magnum/tree/master/magnum/objects">https://github.com/openstack/magnum/tree/master/magnum/objects</a> , we don't change object versions.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">The idea of objects is that each change in their fields should be versioned, documentation about the change should also be written in a comment inside the object and the obj_make_compatible method should be implemented or updated. See an
example here:<o:p></o:p></p>
<p class="MsoNormal"><a href="https://github.com/openstack/nova/commit/ad6051bb5c2b62a0de6708cd2d7ac1e3cfd8f1d3#diff-7c6fefb09f0e1b446141d4c8f1ac5458L27">https://github.com/openstack/nova/commit/ad6051bb5c2b62a0de6708cd2d7ac1e3cfd8f1d3#diff-7c6fefb09f0e1b446141d4c8f1ac5458L27</a><o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">The question is, do you think magnum should support rolling upgrades from next release or maybe it's still too early?<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">If yes, I think core reviewers should start checking for these incompatible changes.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">To clarify, rolling upgrades means support for running magnum services at different versions at the same time.<o:p></o:p></p>
<p class="MsoNormal">In Nova, there is an RPC call in the conductor to backport objects, which is called when older code gets an object it doesn’t understand. This patch does this in Magnum:
<a href="https://review.openstack.org/#/c/184791/">https://review.openstack.org/#/c/184791/</a> .<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I can report bugs and propose patches with version changes for this release, to get the effort started.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">In Mitaka, when Grenade gets multi-node support, it can be used to add CI tests for rolling upgrades in Magnum.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">/ Greg<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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