[openstack-dev] [Nova][Neutron]What's the problem if there is no port status 'up' notification sent from neutron, while creating VM

Kevin Benton kevin at benton.pub
Thu Jun 30 05:13:05 UTC 2016

The VM is paused until the 'up' notification to give the Neutron backend
time to wire up the port.

On Tue, Jun 28, 2016 at 7:59 PM, <kangjingting at sina.com> wrote:

>  Hi guys:
> As we know, nova will interacts with neutron for port creating and
> configuration while creating VM.
> In the method /nova/virt/libvirt/driver.py:_create_domain_and_network,
> here nova ultilizes event mechanism(sqlalchemy) to monitor port status in
> neutron DB. After having subscribed event from neutron DB for port status
> update, it will wait for the event sent from neutron. Finally nova revceive
> port status update event sent from neutron server, which means port is
> ready and the creating of VM will almost complete. But it seems like the
> creating of VM will fail if nova not receive event after the timeout
> period(default 300s).
> What the problem I have encountered is that the VM have been created
> successfully without the notification event send from neutron. Using
> command "nova show VM-ID" shows all states of VM are correct(vm_state:
> active and power state: running). Let's assume a scenario where we replace
> neutron agent with controller, as in the case of OVN, dragonflow, ODL,etc.
> There is an example to support port 'up' or 'down ' notification in
> project OVN. Please refer to this link:
> https://review.openstack.org/#/c/178826/
> So, anyone can give an explanation what's the purpose of the event? Dose
> the event have any impact on creating of VM? Any comment will be
> appreciated, thanks!
> Best Regard!
> Jingting
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