On 12/04/2015 11:50 PM, Michał Jastrzębski wrote:
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.
From Nova's perspective, most of the above looks OK to me, however, I
am in more in favor of an upgrade strategy that builds a "new" set of
conductor or controller service containers all at once and then flips
the VIP or managed IP from the current controller pod containers to the
newly-updated controller pod containers.
This seems to me to be the most efficient (in terms of minimal overall
downtime) and most robust (because a "rollback" is simply flipping the
VIP back to the original controller/conductor service pod containers)
solution for upgrading Nova.
Dan Smith, can you comment on this since you are the God of Upgrades?
Best,
-jay
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