[openstack-dev] [Nova][Neutron] Status of the nova-network to Neutron migration work
amuller at redhat.com
Mon Mar 30 13:25:57 UTC 2015
----- Original Message -----
> On 03/27/2015 11:48 AM, Assaf Muller wrote:
> > ----- Original Message -----
> >> On 03/27/2015 05:22 AM, Thierry Carrez wrote:
> >> <snip>
> >>> Part of it is corner (or simplified) use cases not being optimally
> >>> served by Neutron, and I think Neutron could more aggressively address
> >>> those. But the other part is ignorance and convenience: that Neutron
> >>> thing is a scary beast, last time I looked into it I couldn't make sense
> >>> of it, and nova-network just works for me.
> >>> That is why during the Ops Summit we discussed coming up with a
> >>> migration guide that would explain the various ways you can use Neutron
> >>> to cover nova-network use cases, demystify a few dark areas, and outline
> >>> the step-by-step manual process you can go through to migrate from one
> >>> to the other.
> >>> We found a dev/ops volunteer for writing that migration guide but he was
> >>> unfortunately not allowed to spend time on this. I heard we have new
> >>> volunteers, but I'll let them announce what their plans are, rather than
> >>> put words in their mouth.
> >>> This migration guide can happen even if we follow the nova-net spinout
> >>> plan (for the few who want to migrate to Neutron), so this is a
> >>> complementary solution rather than an alternative. Personally I doubt
> >>> there would suddenly be enough people interested in nova-net development
> >>> to successfully spin it out and maintain it. I also agree with Russell
> >>> that long-term fragmentation at this layer of the stack is generally not
> >>> desirable.
> >> I think if you boil everything down, you end up with 3 really important
> >> differences.
> >> 1) neutron is a fleet of services (it's very micro service) and every
> >> service requires multiple and different config files. Just configuring
> >> the fleet is a beast if it not devstack (and even if it is)
> >> 2) neutron assumes a primary interesting thing to you is tenant secured
> >> self service networks. This is actually explicitly not interesting to a
> >> lot of deploys for policy, security, political reasons/restrictions.
> >> 3) neutron open source backend defaults to OVS (largely because #2). OVS
> >> is it's own complicated engine that you need to learn to debug. While
> >> Linux bridge has challenges, it's also something that anyone who's
> >> worked with Linux & Virtualization for the last 10 years has some
> >> experience with.
> >> (also, the devstack setup code for neutron is a rats nest, as it was
> >> mostly not paid attention to. This means it's been 0 help in explaining
> >> anything to people trying to do neutron. For better or worse devstack is
> >> our executable manual for a lot of these things)
> >> so.... that being said, I think we need to talk about "minimum viable
> >> neutron" as a model and figure out how far away that is from n-net. This
> >> week at the QA Sprint, Dean, Sean Collins, and I have spent some time
> >> hashing it out, hopefully with something to show the end of the week.
> >> This will be the new devstack code for neutron (the old lib/neutron is
> >> moved to lib/neutron-legacy).
> >> Default setup will be provider networks (which means no tenant
> >> isolation). For that you should only need neutron-api, -dhcp, and -l2.
> >> So #1 is made a bunch better. #2 not a thing at all. And for #3 we'd
> >> like to revert back to linux bridge for the base case (though first code
> >> will probably be OVS because that's the happy path today).
> > Looking at the latest user survey, OVS looks to be 3 times as popular as
> > Linux bridge for production deployments. Having LB as the default seems
> > like an odd choice. You also wouldn't want to change the default before
> > LB is tested at the gate.
> Sure, actually testing defaults is presumed here. I didn't think it
> needed to be called out separately.
Quick update about OVS vs LB:
Sean M. Collins pushed up a patch that runs CI on Tempest with LB:
So far it's failing pretty badly.
> Sean Dague
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