[magnum][heat] Rolling system upgrades

feilong feilong at catalyst.net.nz
Tue Feb 2 02:22:55 UTC 2021

HI Krzysztof,

For the first point, at least for new node, we probably need to update
the image ID of the Heat template. But for existing node, there is no
way to update the image ID because it's a readonly attribute from Nova
perspective. And I agree a non-invasive way would be good. I'm going to
discuss with Heat team to understand if there is a pre-update hook we
can leverage to drain before updating the OS. I will keep you posted.

On 26/01/21 9:42 pm, Krzysztof Klimonda wrote:
> Hi Feilong,
> Regarding first point, could you share your idea on how to fix it? I haven't yet put much thought into that, but solving system-level upgrades for nodes (and getting it to work with auto healing/auto scaling etc.) is something I'll have to tackle myself if we want to go into production with full feature-set, and I'd be happy to put work into that.
> Regarding image updates, perhaps that has been fixed since ussuri? I'm testing it on some ussuri snapshot, my nodes use images for root disk, and I can see that the updated image property from cluster template is not populated into heat stack itself.
> I see your point about lack of communication from magnum to the cluster, but perhaps that could be handled in a similar way as OS::Heat::Software* updates, with an agent running on nodes? Perhaps heat's pre-update hook could be used, with agent clearing it after node has been drained. I'm not overly familiar with heat inner workings, and I was hoping that someone with more heat experience could chime in and give some idea how that could be handled.
> Perhaps OS::Heat::Software* resources already provide a way to handle this (although I'm not sure how could that work given that they are probably updated only after server resource update is processed).
> I feel like getting images to update in a non-invasive way would be a cleaner and safer way of handling OS-level upgrades, although I'm not sure how feasible it is in the end.
Cheers & Best regards,
Feilong Wang (王飞龙)
Senior Cloud Software Engineer
Tel: +64-48032246
Email: flwang at catalyst.net.nz
Catalyst IT Limited
Level 6, Catalyst House, 150 Willis Street, Wellington

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