[openstack-dev] [devstack] [neutron] How to tell a compute host the control host is running Neutron

Kyle Mestery mestery at noironetworks.com
Tue Mar 4 02:36:36 UTC 2014

devstack folks:

Per my review here [1] and comments in the review, I wanted to send this
email to try and clarify what I think is being lost in the review comments.
Currently, devstack has no way to configure a compute host running with
Neutron on the control node which has no Neutron services on the compute
host. In all cases today with Open Source plugins, Neutron agents have run
on the hosts. For OpenDaylight, this is not the case. OpenDaylight
integrates with Neutron as a ML2 MechanismDriver. But it has no Neutron
code on the compute hosts. OpenDaylight itself communicates directly to
those compute hosts to program Open vSwitch.

devstack doesn't provide a way for me to express this today. On the compute
hosts in the above scenario, there is no "q-*" services enabled, so the
"is_neutron_enabled" function returns 1, meaning no neutron. And then
devstack sets Nova up to use nova-networking, which fails.

The patch I have submitted [1] modifies "is_neutron_enabled" to check for
the meta neutron service being enabled, which will then configure nova to
use Neutron instead of nova-networking on the hosts. If this sounds wonky
and incorrect, I'm open to suggestions on how to make this happen.

Note: I have another patch [2] which enables an OpenDaylight service,
including configuration of OVS on hosts. But I cannot check if the
"opendaylight" service is enabled, because this will only run on a single
node, and again, not on each compute host.

To me, this is a simple case of no one having tried a configuration like
this with an existing Neutron plugin and multinode devstack.


[1] https://review.openstack.org/#/c/77328/
[2] https://review.openstack.org/#/c/69774/
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