Open Stack

Hey guys,

Orchiestrated upgrades is one of our highest priorities for M in kolla, so
following up after discussion on summit I'd like to suggest an approach:

Instead of creating playbook called "upgrade my openstack" we will create
"upgrade my nova" instead and approach to each service case by case (since
all of our running services are in dockers, this is possible).
We will also make use of image tags as version carriers, so ansible will
deploy new container only if version tag differs from what we ask it to
deploy. This will help with idempotency of upgrade process.

So let's start with nova. Upgrade-my-nova playbook will do something like
this:

0. We create snapshot of our mariadb-data container. This will affect every
service, but it's always good to have backup and rollback of db will be
manual action

1. Nova bootstrap will be called and it will perform db-migration. Since
current approach to nova code is add-only we shouldn't need to stop
services and old services should keep working on newer database. Also for
minor version upgrades there will be no action here unless there is
migration.
2. We upgrade all conductor at the same time. This should take mere seconds
since we'll have prebuilt containers
3. We will upgrade rest of controller services with using "series: 1" in
ansible to ensure rolling upgrades.
4. We will upgrade all of nova-compute services on it's own pace.

This workflow should be pretty robust (I think it is) and it should also
provide idempotency.

Thoughts?

Regards,
Michal
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