Prior to this patch, the metadata agent was writing into SB
database when a network had been provisioned with metadata
on a particular chassis.
Then, neutron-server would wait for that event to happen with
a 15s timeout before sending the vif-plugged event to Nova.
By removing this mechanism:
1) We'll save writes to OVN SB database which, in highly loaded
systems and at scale reduces significantly the load on ovsdb-server.
2) Ignoring healthchecks (that still requires write to the SB DB),
we can make OVN metadata agent to connect to slave instances when
using active-backup OVN databases since writes are not needed.
3) There's a chance that the VM boots very fast and requests
metadata before the service is ready but since the timeout was
15 seconds, we can safely rely on the the cloud-init retries.
Signed-off-by: Daniel Alvarez Sanchez <dalvarez@redhat.com>
Change-Id: Ia6cd7a9a3b9662a9a8ce106e01a93c357c255956
36ba1cc319