I agree. I feel like this is another example of functionality which is trivially implemented outside nova, and where it works much better if we don't do it. Couldn't an admin just have a cron job which verifies hosts, and then adds them to a compromised-hosts host aggregate if they're owned? I assume without testing it that you can migrate instances _out_ of a host aggregate you can't boot in?
Michael On Tue, Jun 23, 2015 at 8:41 PM, Sylvain Bauza <sba...@redhat.com> wrote: > Hi team, > > Some discussion occurred over IRC about a bug which was publicly open > related to TrustedFilter [1] > I want to take the opportunity for raising my concerns about that specific > filter, why I dislike it and how I think we could improve the situation - > and clarify everyone's thoughts) > > The current situation is that way : Nova only checks if one host is > compromised only when the scheduler is called, ie. only when > booting/migrating/evacuating/unshelving an instance (well, not exactly all > the evacuate/live-migrate cases, but let's not discuss about that now). When > the request goes in the scheduler, all the hosts are checked against all the > enabled filters and the TrustedFilter is making an external HTTP(S) call to > the Attestation API service (not handled by Nova) for *each host* to see if > the host is valid (not compromised) or not. > > To be clear, that's the only in-tree scheduler filter which explicitly does > an external call to a separate service that Nova is not managing. I can see > at least 3 reasons for thinking about why it's bad : > > #1 : that's a terrible bottleneck for performance, because we're IO-blocking > N times given N hosts (we're even not multiplexing the HTTP requests) > #2 : all the filters are checking an internal Nova state for the host > (called HostState) but that the TrustedFilter, which means that conceptually > we defer the decision to a 3rd-party engine > #3 : that Attestation API services becomes a de facto dependency for Nova > (since it's an in-tree filter) while it's not listed as a dependency and > thus not gated. > > > All of these reasons could be acceptable if that would cover the exposed > usecase given in [1] (ie. I want to make sure that if my host gets > compromised, my instances will not be running on that host) but that just > doesn't work, due to the situation I mentioned above. > > So, given that, here are my thoughts : > a/ if a host gets compromised, we can just disable its service to prevent > its election as a valid destination host. There is no need for a specialised > filter. > b/ if a host is compromised, we can assume that the instances have to > resurrect elsewhere, ie. we can call a nova evacuate > c/ checking if an host is compromised or not is not a Nova responsibility > since it's already perfectly done by [2] > > In other words, I'm considering that "security" usecase as something analog > as the HA usecase [3] where we need a 3rd-party tool responsible for > periodically checking the state of the hosts, and if compromised then call > the Nova API for fencing the host and evacuating the compromised instances. > > Given that, I'm proposing to deprecate TrustedFilter and explictly mention > to drop it from in-tree in a later cycle https://review.openstack.org/194592 > > Thoughts ? > -Sylvain > > > > [1] https://bugs.launchpad.net/nova/+bug/1456228 > [2] https://github.com/OpenAttestation/OpenAttestation > [3] http://blog.russellbryant.net/2014/10/15/openstack-instance-ha-proposal/ > > > __________________________________________________________________________ > OpenStack Development Mailing List (not for usage questions) > Unsubscribe: openstack-dev-requ...@lists.openstack.org?subject:unsubscribe > http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev -- Rackspace Australia __________________________________________________________________________ OpenStack Development Mailing List (not for usage questions) Unsubscribe: openstack-dev-requ...@lists.openstack.org?subject:unsubscribe http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev