Merge lp:~soren/nova/only-start-one-dnsmasq into lp:~hudson-openstack/nova/trunk

[Soren Hansen]

Wrap update_dhcp in utils.synchronized.

From the linked bug:

"When I reinstall my test environment and start running instances on it, usually only one of the first batch succeeds, the rest are stuck in "networking" state. After that everything is fine and I can run many concurrent RunInstances calls.

I'm not completely sure, but my working hypothesis is each thread finds that dnsmasq isn't running, and then tries to start it, all at roughly the same time. Only one succeeds, though, because only one process can listen on the socket at any given time."

The hypothesis held up, adding this lock has completely solved the problem.

This change is crucial for the automated integration tests to be integrated into the patch acceptance workflow. Without it, the first round of tests after a clean install will fail.

[Matt Dietz (cerberus)]

Makes sense to me.

review: Approve

[Vish Ishaya (vishvananda)]

lgtm

review: Approve

=== modified file 'nova/network/linux_net.py'
--- nova/network/linux_net.py	2011-03-18 13:56:05 +0000
+++ nova/network/linux_net.py	2011-03-21 09:08:37 +0000
@@ -557,6 +557,7 @@
 # NOTE(ja): Sending a HUP only reloads the hostfile, so any
 #           configuration options (like dchp-range, vlan, ...)
 #           aren't reloaded.
[e-mail]('dnsmasq_start')
 def update_dhcp(context, network_id):
     """(Re)starts a dnsmasq server for a given network