[openstack-dev] [Nova][Neutron] Linuxbridge as the default in DevStack [was: Status of the nova-network to Neutron migration work]

Sean M. Collins sean at coreitpro.com
Fri Apr 10 18:03:48 UTC 2015

We already tried to make Neutron the default with OVS - and the results
were not good[1].

Operators who are currently not using Neutron have said that they do
not want to learn both Neutron and also Open vSwitch at the same time.

This was documented at the operator's summit. We clearly have a
stumbling block - Open vSwitch.



Based on discussions we had at the QA sprint, the idea is to start with
a very simple Neutron configuration in DevStack, so that we can remove
nova-network as the default. The argument is that the people
who are still using nova-network are comfortable with Linux Bridge, and
that having Linux Bridge as the default Neutron agent will serve as
a "bridge" (no pun intended) into the Neutron world.

There will be *clear* documentation that this is a very simplistic
model, and it will be made obvious that for more advanced scenarios you
will need to configure your local.conf to use the Open vSwitch agent.

I've spoken with Sean Dague about testing Linux Bridge and
the idea is that we should have test coverage of both OVS and Linux
Bridge, and that currently there is a gap with Linux Bridge. I think
that it's OK if we override the default at the gate to run OVS, since
that has the most test coverage and will cause the least disruption.
There will be jobs created, that will test Linux Bridge similar to how
Open vSwitch is tested at the gate today.

As a DevStack user, I would like to see Neutron as the default. After
making Neutron the default, the changes needed for the local.conf file
for me to run my mechanism driver of choice is significantly smaller
than the changes needed today for my local.conf/localrc to
disable Nova-Network, enable Neutron, and run my mechanism driver of choice.

If Linux Bridge being the default is the way to make the above happen,
so be it.

[1]: https://review.openstack.org/#/c/153208/

Sean M. Collins

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