Comment 10 for bug 1378904

There is clear upstream consensus on the fact that since availability zones are for end-users, updating an AZ from an operator point-of-view would confuse their users.

Let me explain further : say you'd like to change AZ "foo" into "bar". For end-users looking at the AZ API before booting their instances, they can see "foo" as a valid target. So they just use --availability_zone foo in their instance boot calls and they expect to see their instances in AZ foo.

Now, what if operator turns "foo" into "bar" ? If I'm an end-user, I'd be very surprised to see my instances being now in "bar" while I explicitely asked "foo"!

As a clear design decision, we really want to make it explicit that renaming an AZ should be forbidden if there are active instances hosted within that AZ.
Closing that bug as Wontfix since I feel not being able to modify an AZ is not a bug but rather a design decision, but I feel we also need to modify the aggregates API to return a HTTP40x if someone is wanting to update an aggregate metadata containing AZ information when there are instances attached to it.