os_region_name should be required to prevent RegionAmbiguity when new endpoint added

[Mat Lowery]

Today, you can leave os_region_name unspecified and, given a single endpoint per service type (i.e. no service is in multiple regions), you'll get that endpoint when looking it up. However, add an additional endpoint for a given type (in another region) and you'll suddenly get RegionAmbiguity errors. To prevent this, always require os_region_name.

[Mat Lowery (mat-lowery)]

As I originally captured this bug, it's really dictating a solution to a problem. Let's start with the problem itself first: Adding a new Nova endpoint (or any endpoint needed by Trove services) means that you'll get a RegionAmbiguity error (in a otherwise perfectly functioning Trove deployment) because, by default, os_region_name isn't set. So without the region, you get more than one endpoint for Nova and Trove raises the exception.

Some possible solutions:

1. If you make os_region_name required, but leave it as None, then Trove won't "work out of the box".

2. If you make os_region_name required and set the os_region_name out of the box, what do you set it to? DevStack's region (I think it's called RegionOne)?

3. Stop raising RegionAmbiguity errors and just take any endpoint. I'm not sure this is very wise given you could get endpoints that are not ideal in terms of performance.

4. Trove determines what region it's in and looks up other services based on the region that matches its own. I can't think of how this is possible.

Given all this typing, I guess I still like #2.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/140121

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/140121
Committed: https://git.openstack.org/cgit/openstack/trove/commit/?id=0220e1cd5ade19a54c708fb565fa432e2d7be053
Submitter: Jenkins
Branch: master

commit 0220e1cd5ade19a54c708fb565fa432e2d7be053
Author: Victoria Martinez de la Cruz <email address hidden>
Date: Mon Dec 8 16:00:23 2014 -0300

    Assign os_region_name a default value

    Leaving os_region_name is unspecified leads to RegionAmbiguity errors.
    Defaulting to RegionOne (DevStacks default) allows Trove working
    out-of-the-box with DevStack and, in the more common case of not being
    in a DevStack environment, it will fail with a NoServiceEndpoint error.

    Change-Id: I772e6698566c4c8e43ec5aebea5ac9362ce01ee7
    Closes-Bug: #1361377