I've been investigating a bug that is preventing VM's from receiving IP 
addresses when a Neutron service is under high load:

https://bugs.launchpad.net/neutron/+bug/1192381

High load causes the DHCP agent's status updates to be delayed, causing the 
Neutron service to assume that the agent is down.  This results in the Neutron 
service not sending notifications of port addition to the DHCP agent.  At 
present, the notifications are simply dropped.  A simple fix is to send 
notifications regardless of agent status.  Does anybody have any objections to 
this stop-gap approach?  I'm not clear on the implications of sending 
notifications to agents that are down, but I'm hoping for a simple fix that can 
be backported to both havana and grizzly (yes, this bug has been with us that 
long).

Fixing this problem for real, though, will likely be more involved.  The 
proposal to replace the current wsgi framework with Pecan may increase the 
Neutron service's scalability, but should we continue to use a 'fire and 
forget' approach to notification?  Being able to track the success or failure 
of a given action outside of the logs would seem pretty important, and allow 
for more effective coordination with Nova than is currently possible.


Maru
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