Hello,
I wanted to start discussion about versioned objects backporting for
conductor-less projects.
In Vancouver we discussed compatibility mode, which works like that:
1. We define one version for every object we use, this means adding base
object, for example:
Class HeatObject:
VERSION=1.5
All objects inherit from this one, each time we change it, we bump up this
variable.
2. We introduce new config option in heat.conf
Combatibility_mode = 1.4
3. Implement mechanism which will automatically backport each outgoing message
to 1.4 as long as we have this var.
Upgrade flow looks like that:
1. We have all nodes using 1.4 version
2. We incrementally run new version with 1.4 compatibility mode
3. When all nodes are already up-to-date, we incrementally turn off
compatibility mode
This solution has one rather big disadvantage: 2 restarts.
This can be mitigated by adding another call to reread config without restart.
Oslo.config has this capability, but we need to add call to run it.
Thoughts?
Regards,
Michał Jastrzębski
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