RFC: #786844 - Detection of deleted instances

Matt Wagner matt.wagner at redhat.com
Thu Feb 9 00:05:58 UTC 2012


Hi all,

I was looking at https://bugzilla.redhat.com/show_bug.cgi?id=786844 and
ended up establishing somewhat of a rambling commentary in the comments.

Basically, the issue is that if you launch an instance in Conductor, and
then go into the cloud provider and *remove* the instance outside of
Conductor, we never pick up any updates on the instance, showing it as
running in perpetuity.

The reason this happens is that we process these updates by retrieving
the list of instances from the provider via Deltacloud, and updating the
status for each of them. But since cloud providers don't report back
deleted instances, they aren't passed to Deltacloud, or, in turn, us.

There are a few possible fixes:

a.) Do nothing, but document that if you remove instances outside of
Conductor, we won't pick up on them. This is a valid course of action, I
think, but probably not the best.

b.) After retrieving the updates, also go through our database and, for
any that weren't in the list of instances, delete them from our
database. This seems extreme, though, if only because I fear what will
happen if there's some transient error.

c.) Add a new instance state, "vanished" or something to that effect,
and update the status to that instead of deleting it. I think this is my
favorite option, but I'm not sure what it actually accomplishes. It
seems like there's still a lot of work we'd want to do around this, such
as some sort of special highlight in the UI, and also making sure that
you're able to delete 'vanished' instances without a problem. (But,
again, there's the issue of what happens if delete an instance because
of a transient error you're not aware of.)

Does anyone else want to weigh in? I'm just worried that we might be
opening a big can of worms here.

-- Matt



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