Open Stack

+1 -- Can't wait to talk about this more. This is a big blocker across all projects from a CI/CD standpoint.


On Mar 11, 2013, at 5:25 PM, Mark Washenberger <mark.washenberger at markwash.net> wrote:

> Hi Tom,
> 
> Unfortunately, Glance does not support rolling db upgrades. Actually,
> I'm not aware of any OpenStack project that supports such upgrades. So
> far, I believe that deployments that require very high uptime are
> advised to carefully manage and even at times rewrite the database
> migrations.
> 
> I'm not happy with this situation, and supporting rolling upgrades in
> Glance is on my personal roadmap. However, there are number of
> difficult issues we need to tackle to make that work. First we'll need
> to refactor the code away from the use of declarative sqlalchemy
> models, towards an approach that allows the domain models and database
> schemas to be versioned independently. Second, we'll need to come up
> with a testing procedure that can enforce the practices that make
> rolling upgrades possible. Last (that I know of) we'll need to figure
> out a way to communicate the relative significance of each commit to
> deployers, as each can have potentially different strategies for the
> best way to distribute the change out into their cluster. If we do
> eventually provide support for rolling upgrades, its going to be a
> daunting task, made much harder by the variety of possible OpenStack
> deployments that need to be considered.
> 
> This is a subject I'm very excited about. If there are others with
> ideas for how we might make progress towards rolling upgrades, I'm
> very happy to brainstorm about ways to incorporate these ideas into
> Glance. I anticipate adding support will be easier in Glance, due to
> the relative simplicity of the project and its data model.
> 
> Thanks,
> markwash
> 
> On Mon, Mar 11, 2013 at 4:55 AM, Hancock, Tom (HP Cloud Services)
> <Tom.Hancock at hp.com> wrote:
>> I’m happy to be corrected on this as I’m basing it on reading a diff, not an
>> actual test.
>> 
>> It looks like glance migration 19 could introduce a non backwards compatible
>> change
>> 
>> to the glance database. In principle, how should such an upgrade be managed?
>> 
>> 
>> 
>> A ‘rolling’ upgrade would be an ideal way to minimize disruptive updates.
>> 
>> It looks like there would need to be a bounce upgrade (stop the service on
>> all nodes;
>> 
>> upgrade sw; start service) as old and new db clients don’t look like they
>> will co-exist.
>> 
>> 
>> 
>> thanks,
>> 
>> Tom
>> 
>> 
>> 
>> ---
>> 
>> Tomas Hancock, HP Cloud Services, Hewlett Packard, Galway. Ireland
>> +353-91-754765
>> 
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