[openstack-dev] [neutron][db] online schema upgrades

Ihar Hrachyshka ihrachys at redhat.com
Wed Jun 17 16:39:10 UTC 2015

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On 06/16/2015 05:58 PM, Mike Bayer wrote:
> On 6/16/15 11:41 AM, Ihar Hrachyshka wrote:
>> -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256
>> - - instead of migrating data with alembic rules, migrate it in
>> runtime. There should be a abstraction layer that will make sure
>> that data is migrated into new schema fields and objects, while
>> preserving data originally stored in 'old' schema elements.
>> That would allow old neutron-server code to run against new
>> schema (it will just ignore new additions); and new
>> neutron-server code to gradually migrate data into new
>> columns/fields/tables while serving user s.
> Hi Ihar -
> I was in the middle of writing a spec for neutron online schema 
> migrations, which maintains "expand / contract" workflow but also 
> maintains Alembic migration scripts.   As I've stated many times in
> the past, there is no reason to abandon migration scripts, while
> there are many issues related to abandoning the notion of the
> database in a specific versioned state as well as the ability to
> script any migrations whatsoever.   The spec amends Nova's approach
> and includes upstream changes to Alembic such that both approaches
> can be supported using the same codebase.

I probably don't follow completely. It was not my intent to propose
complete abandonment of migration scripts. In any case, eagerly
waiting for your proposal in gerrit. :)

Note that now that neutron process leans more to RFEs in Launchpad, it
may be the case that a better place for the description of your
proposal is in neutron's devref. Anyway, we'll see.

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