[openstack-dev] [Neutron] Calling a controller from within a session in the plugin

Aaron Rosen aaronorosen at gmail.com
Thu Dec 5 00:56:02 UTC 2013

In my experience doing any kind of http request inside a of a db
transaction kills performance vastly (and can lead to situations where
deadlock often occurs due to eventlet+sqlalchemly). This topic also was
recently discussed here:



On Wed, Dec 4, 2013 at 9:15 AM, Mohammad Banikazemi <mb at us.ibm.com> wrote:

> Have a question regarding calling an external SDN controller in a plugin.
> The ML2 model brings up the fact that it is preferred not to call an
> external controller within a database session by splitting up each call
> into two calls: *_precommit and *_postcommit. Makes sense.
> Looking at the existing monolithic plugins, I see some plugins that do not
> follow this approach and have the call to the controller from within a
> session. The obvious benefit of this approach would be a simpler cleanup
> code segment for cases where the call to controller fails. So my question
> is whether it is still OK to use this simpler approach in monolithic
> plugins. As we move to the ML2 model, we will be using the ML2 approach but
> in the meantime, we leave the option of calling the controller within a
> session as an OK option. Would that be reasonable?
> -Mohammad
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