[RFE] for rolling upgrades, pin the API version

[Ruby Loo]

Now that we have the rolling upgrades infrastructure in place, let's refine it! During a rolling upgrade, the new ironic-api and ironic-conductor services are pinned so that they use the same RPC vesions and IronicObject versions as the older service (thus allowing them to talk to each other without getting upset).

For the ironic-api service, we should also pin the API microversion. Pinning this would:

- make it easier for the new ironic-api services to know when/how to reject new features that the old ironic-api services cannot handle. They would return HTTP code 406 (Not Acceptable)
- change the response header so that the maximum API version would be the pinned version

This would take effect using the same [DEFAULT]pin_release_version configuration option, so no extra things for the operator to do .

Documentation will be updated to reflect this.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/518411

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/518648

[Ruby Loo (rloo)]

Discussed in ironic meeting [1]. Dmitry and Julia are good with this.

[1] http://eavesdrop.openstack.org/meetings/ironic/2017/ironic.2017-11-20-17.00.log.html#l-268

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/518411
Committed: https://git.openstack.org/cgit/openstack/ironic/commit/?id=feac8cfb786f7490743b3f270aa569054795ef4f
Submitter: Zuul
Branch: master

commit feac8cfb786f7490743b3f270aa569054795ef4f
Author: Ruby Loo <email address hidden>
Date: Tue Nov 7 17:47:40 2017 -0500

    Pin API version during rolling upgrade

    During a rolling upgrade, when the new services are pinned to the
    old release, the API version will also be pinned to the old release.
    This will prevent users from accessing new features that may not quite
    work.

    The .sample was updated to reflect the change to the help string for
    the [DEFAULT]/pin_release_version configuration option. The update also
    pulled in changes for other options, from other (non-ironic) libraries.

    Change-Id: I38a0f106b589945fb62071f3dfe5bff43c6fee93
    Partial-Bug: #1708549

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/518648
Committed: https://git.openstack.org/cgit/openstack/ironic/commit/?id=76312313d4ab43a84a9069108bbce5befabcc689
Submitter: Zuul
Branch: master

commit 76312313d4ab43a84a9069108bbce5befabcc689
Author: Ruby Loo <email address hidden>
Date: Wed Nov 8 22:59:57 2017 -0500

    Update docs to include API version pinning

    This updates the documentation to include API version pinning
    during the rolling upgrade process.

    Change-Id: I493cd6229a8bd68720da4d5c25983a3662f4f35a
    Closes-Bug: #1708549

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/ironic 10.0.0 release.