Open Stack

On Fri, 2018-10-12 at 17:05 -0500, Matt Riedemann wrote:
> The big update this week is version 0.1.0 of oslo.upgradecheck was 
> released. The documentation along with usage examples can be found
> here 
> [1]. A big thanks to Ben Nemec for getting that done since a few 
> projects were waiting for it.
> 
> In other updates, some changes were proposed in other projects [2].
> 
> And finally, Lance Bragstad and I had a discussion this week [3]
> about 
> the validity of upgrade checks looking for deleted configuration 
> options. The main scenario I'm thinking about here is FFU where
> someone 
> is going from Mitaka to Pike. Let's say a config option was
> deprecated 
> in Newton and then removed in Ocata. As the operator is rolling
> through 
> from Mitaka to Pike, they might have missed the deprecation signal
> in 
> Newton and removal in Ocata. Does that mean we should have upgrade 
> checks that look at the configuration for deleted options, or
> options 
> where the deprecated alias is removed? My thought is that if things
> will 
> not work once they get to the target release and restart the service 
> code, which would definitely impact the upgrade, then checking for
> those 
> scenarios is probably OK. If on the other hand the removed options
> were 
> just tied to functionality that was removed and are otherwise not 
> causing any harm then I don't think we need a check for that. It was 
> noted that oslo.config has a new validation tool [4] so that would
> take 
> care of some of this same work if run during upgrades. So I think 
> whether or not an upgrade check should be looking for config option 
> removal ultimately depends on the severity of what happens if the
> manual 
> intervention to handle that removed option is not performed. That's 
> pretty broad, but these upgrade checks aren't really set in stone
> for 
> what is applied to them. I'd like to get input from others on this, 
> especially operators and if they would find these types of checks
> useful.
> 
> [1] https://docs.openstack.org/oslo.upgradecheck/latest/
> [2] https://storyboard.openstack.org/#!/story/2003657
> [3] 
> http://eavesdrop.openstack.org/irclogs/%23openstack-dev/%23openstack-dev.2018-10-10.log.html#t2018-10-10T15:17:17
> [4] 
> http://lists.openstack.org/pipermail/openstack-dev/2018-October/135688.html
> 

Hey,

Nice topic, thanks Matt!

TL:DR; I would rather fail explicitly for all removals, warning on all
deprecations. My concern is, by being more surgical, we'd have to
decide what's "not causing any harm" (and I think deployers/users are
best to determine what's not causing them any harm).
Also, it's probably more work to classify based on "severity".
The quick win here (for upgrade-checks) is not about being smart, but
being an exhaustive, standardized across projects, and _always used_
source of truth for upgrades, which is complemented by release notes.

Long answer:

At some point in the past, I was working full time on upgrades using
OpenStack-Ansible.

Our process was the following:
1) Read all the project's releases notes to find upgrade documentation
2) With said release notes, Adapt our deploy tools to handle the
upgrade, or/and write ourselves extra documentation+release notes for
our deployers.
3) Try the upgrade manually, fail because some release note was missing
x or y. Find root cause and retry from step 2 until success.

Here is where I see upgrade checkers improving things:
1) No need for deployment projects to parse all release notes for
configuration changes, as tooling to upgrade check would be directly
outputting things that need to change for scenario x or y that is
included in the deployment project. No need to iterate either.

2) Test real deployer use cases. The deployers using openstack-ansible
have ultimate flexibility without our code changes. Which means they
may have different code paths than our gating. Including these checks
in all upgrades, always requiring them to pass, and making them
explicit about the changes is tremendously helpful for deployers:
- If config deprecations are handled as warnings as part of the same
process, we will output said warnings to generate a list of action
items for the deployers. We would use only one tool as source of truth
for giving the action items (and still continue the upgrade);
- If config removals are handled as errors, the upgrade will fail,
which is IMO normal, as the deployer would not have respected its
action items.

In OSA, we could probably implement a deployer override (variable). It
would allow the deployers an explicit bypass of an upgrade failure. "I
know I am doing this!". It would be useful for doing multiple serial
upgrades.

In that case, deployers could then share together their "recipes" for
handling upgrade failure bypasses for certain multi-upgrade (jumps)
scenarios. After a while, we could think of feeding those back to
upgrade checkers.

3) I like the approach of having oslo-config-validator. However, I must
admit it's not part of our process to always validate a config file
before trying to start a service in OSA. I am not sure where other
deployment projects are in terms of that usage. I am not familiar with
upgrade checker code, but I would love to see it re-using oslo-config-
validator, as it would be the unique source of truth for upgrades
before the upgrade happens (vs having to do multiple steps).
If I am completely out of my league here, tell me.

Just my 2 cents.
Jean-Philippe Evrard (evrardjp)