nova migrate does not update bridge configuration on destination node

[Joe Breu]

This may be related to https://bugs.launchpad.net/nova/+bug/939060

In Essex/stable, using 'nova migrate' to migrate an instance to another succeeds but the instance does not get a DHCP address on start because the dnsmasq entries for the instance do not get added to the dnsmasq config file.

To duplicate:

1) boot instance
2) on the compute node where the instance is running view the dnsmasq config file (in this case /var/lib/nova/networks/nova-br100.conf). The MAC address is present here.
3) run 'nova migrate' to migrate the instance.
4) on the original source compute node verify that the mac address is still present in the config file
5) on the compute node where the instance is now running verify that the mac address does not exist in the dnsmasq config file

As a result the instance does not get a response from the DHCPDISCOVER.

This can be resolved by restarting nova-network on the source and destination compute nodes and rebooting the instance.

This is present in Essex/stable - I have not verified it in newer releases or trunk.

[Mark McLoughlin (markmc)]

(In case it's not obvious to everyone, this is with multi_host mode)

We expect this to be regenerating the dnsmasq config:

 + # NOTE(vish): this is necessary to update dhcp
 + self.network_api.setup_networks_on_host(context,
 + instance_ref,
 + self.host)

this is called after the instance host field is updated, so you'd expect the dnsmasq config to be regenerated correctly - i.e. linux_net.update_dhcp() should be called and get_dhcp_hosts() should return the instance on the destination host but not on the source note

that code is from stable/essex and was part of the fix for bug #939060

Hard to come to any conclusions without logs. Could you attach compute and network logs from the source and destination hosts?

[Matt Hilt (mjhilt-x)]

I ran into this when trying both migrate and resize. It seems like a fix was already found for Folsom/Quantal: https://bugs.launchpad.net/ubuntu/quantal/+source/nova/+bug/1065440

I've attached the nova-network logs for the two nodes. The IPs in question are:
10.50.18.32 --> nova resize
10.50.18.40 --> nova migrate