On 09/02/2016 12:40 PM, Eric Harney wrote:
On 08/15/2016 04:48 AM, Thierry Carrez wrote:
Sean Dague wrote:
On 08/12/2016 01:10 PM, Walter A. Boring IV wrote:
I believe there is a compromise that we could implement in Cinder that
enables us to have a deprecation
of unsupported drivers that aren't meeting the Cinder driver
requirements and allow upgrades to work
without outright immediately removing a driver.
1. Add a 'supported = True' attribute to every driver.
2. When a driver no longer meets Cinder community requirements, put a
patch up against the driver
3. When c-vol service starts, check the supported flag. If the flag is
False, then log an exception, and disable the driver.
4. Allow the admin to put an entry in cinder.conf for the driver in
question "enable_unsupported_driver = True". This will allow the
c-vol service to start the driver and allow it to work. Log a
warning on every driver call.
5. This is a positive acknowledgement by the operator that they are
enabling a potentially broken driver. Use at your own risk.
6. If the vendor doesn't get the CI working in the next release, then
remove the driver.
7. If the vendor gets the CI working again, then set the supported flag
back to True and all is good.
This allows a deprecation period for a driver, and keeps operators who
upgrade their deployment from losing access to their volumes they have
on those back-ends. It will give them time to contact the community
and/or do some research, and find out what happened to the driver.
This also potentially gives the operator time to find a new supported
backend and start migrating volumes. I say potentially, because the
driver may be broken, or it may work enough to migrate volumes off of it
to a new backend.
Having unsupported drivers in tree is terrible for the Cinder community,
and in the long run terrible for operators.
Instantly removing drivers because CI is unstable is terrible for
operators in the short term, because as soon as they upgrade OpenStack,
they lose all access to managing their existing volumes. Just because
we leave a driver in tree in this state, doesn't mean that the operator
will be able to migrate if the drive is broken, but they'll have a
chance depending on the state of the driver in question. It could be
horribly broken, but the breakage might be something fixable by someone
that just knows Python. If the driver is gone from tree entirely, then
that's a lot more to overcome.
I don't think there is a way to make everyone happy all the time, but I
think this buys operators a small window of opportunity to still manage
their existing volumes before the driver is removed. It also still
allows the Cinder community to deal with unsupported drivers in a way
that will motivate vendors to keep their stuff working.
This seems very reasonable. It allows the cinder team to mark stuff
unsupported at any point that vendors do not meet their upstream
commitments, but still provides some path forward for operators that
didn't realize their chosen vendor abandoned them and the community
until after they are in the midst of upgrade. It's very important that
the cinder team is able to keep a very visible hammer for vendors not
living up to their commitments.
Keeping some visible data around drivers that are flapping (going
unsupported, showing up with CI to get back out of the state,
disappearing again) would be great as well, to further give operators
data on what vendors are working in good faith and which aren't.
I like this a lot, and it certainly would address the deprecation policy
part.
Sean: I was wondering if that would not still be considered breaking
upgrades, though... Since you end up upgrading and your c-vol would not
restart until you set enable_unsupported_driver = True ?
Kind of late jumping in here, but I'm curious what you guys think on
this last point.
I have a similar feeling, that this may still be breaking upgrades in an
undesirable way.
There are softer alternatives that could still communicate that a driver
is unsupported and not halt the upgrade path, such as printing warning
messages when the c-vol service starts up, etc.
It's important to remember that there are 2 goals behind the current policy:
1) Protect end users from buggy/unmaintained drivers.
2) Motivate vendors to actively maintain their drivers by associating a
painful consequence with not maintaining them.
Most of this discussion seems to be about alternative ways to address
the first goal. However the second goal is in direct conflict with many
of the proposed solutions. The more kind and gentle the approach is to
deprecating drivers, the less effective it will be as a motivator for
vendors.
Personally I'm of 2 minds about this. I think it's useful for the
community to have a stick to beat vendors with to keep drivers
maintained, and I think backing off the current driver deletion policy
would turn that stick into a nerf bat. However I also think that in the
long run the market will punish vendors who do a bad job of writing and
maintaining drivers and the community probably doesn't need to expend as
much effort as it does policing driver quality.
-Ben Swartzlander
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