[openstack-dev] disabling deprecated APIs by config?

Sean Dague sean at dague.net
Wed May 18 15:20:41 UTC 2016

nova-net is now deprecated - https://review.openstack.org/#/c/310539/

And we're in the process in Nova of doing some spring cleaning and
deprecating the proxies to other services -

At some point in the future after deprecation the proxy code is going to
stop working. Either accidentally, because we're not going to test or
fix this forever (and we aren't going to track upstream API changes to
the proxy targets), or intentionally when we decide to delete it to make
it easier to address core features and bugs that everyone wants addressed.

However, the world moves forward slowly. Consider the following scenario.

We delete nova-net & the network proxy entirely in Peru (a not entirely
unrealistic idea). At that release there are a bunch of people just
getting around to Newton. Their deployments allow all these things to
happen which are going to 100% break when they upgrade, and people are
writing more and more OpenStack software every cycle.

How do we signal to users this kind of deprecation? Can we give sites
tools to help prevent new software being written to deprecated (and
scheduled for deletion) APIs?

One idea was a "big red switch" in the format of a config option
``disable_deprecated_apis=True`` (defaults to False). Which would set
all deprecated APIs to 404 routes.

One of the nice ideas here is this would allow some API servers to have
this set, and others not. So users could point to the "clean" API
server, figure out that they will break, but the default API server
would still support these deprecated APIs. Or, conversely, the default
could be the clean API server, and a legacy API server endpoint could be
provided for projects that really needed it that included these
deprecated things for now. Either way it would allow some site assisted
transition. And be something like the -Werror flag in gcc.

In the Nova case the kinds of things ending up in this bucket are going
to be interfaces that people *really* shouldn't be using any more. Many
of them data back to when OpenStack was only 2 projects, and the concept
of splitting out function wasn't really thought about (note: we're
getting ahead of this one for the 'placement' rest API, so it won't have
any of these issues). At some point this house cleaning was going to
have to happen, and now seems to be the time to do get it rolling.

Feedback on this idea would be welcomed. We're going to deprecate the
proxy APIs regardless, however disable_deprecated_apis is it's own idea
and consequences, and we really want feedback before pushing forward on


Sean Dague

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