Comment 3 for bug 1486593

Reviewed: https://review.openstack.org/215584
Committed: https://git.openstack.org/cgit/stackforge/os-ansible-deployment/commit/?id=092f606adcd7120195e9a71afe80893a9d512f03
Submitter: Jenkins
Branch: master

commit 092f606adcd7120195e9a71afe80893a9d512f03
Author: Matt Thompson <email address hidden>
Date: Fri Aug 21 12:04:30 2015 +0100

    Update how neutron migrations are handled

    We're seeing some neutron db sync failures in master branch (liberty).
    It looks like there may be a few issues with the way we're handling
    migrations:

    1. We're not capturing the correct information in the 'Check last DB
       revision' task as the first line returned by 'neutron-db-manage
       history' is a header (this also means that the 'Inspect on disk
       neutron DB revision' task will never do what we intend).
    2. We delegate 'Check last DB revision' to 'neutron_all' group, but in
       an ideal world this is probably only necessary on 'neutron_server'.
    3. When stopping neutron server to run 'Perform a Neutron DB Upgrade',
       we're only stopping it on groups['neutron_server'][0], while all
       other neutron server containers are up servicing requests.
    4. Perform a db stamp, which doesn't appear to be necessary.

    This change makes the following changes:

    1. Bumps neutron SHA to include 43c00a9, which introduces new
       --expand / --contract upgrade options (otherwise, you have to
       specify liberty_expand@head / liberty_contract@head which may no
       longer work when neutron gets bumped in the future)
    2. Checks if migrations have previously run, and if not runs a
       'neutron-db-manage upgrade heads'
    3. If migrations have previously run:
       a) it runs an online migration against expand alembic branch using
          'neutron-db-manage upgrade --expand'.
       b) it stops all neutron-server services
       c) it runs an offline migration against contract alembic branch
          using 'neutron-db-manage upgrade --contract'
       d) it starts all neutron-server instances
    4. It removes the temporary pin introduced in
       https://review.openstack.org/218572 as the SHA bump includes the
       upstream fix https://review.openstack.org/218723

    TODO: Currently, we upgrade expand and contract branches (shutting down
          neutron-server in the proceses), even if there are no pending
          migrations. We need to find a clean way to check what migration
          we are on and compare to alembic HEADS file to see if we're up to
          date. Unfortunately, 'neutron-db-manage current' doesn't indicate
          which migration is in which alembic branch, so you would have to
          further grep for each migration in the neutron migrations code to
          determine the branch.

    NOTE: Liberty introduces the split alembic branches for online/offline
          migrations, see [1] for more information.

    [1] http://docs.openstack.org/developer/neutron/devref/alembic_migrations.html

    Change-Id: I1176b5fe12cad1ee732486ae179e76deea5623e1
    Closes-Bug: #1486593