[openstack-dev] [neutron] ML2 plugin swallows mechanism driver exceptions

Andre Pech apech at aristanetworks.com
Fri Jan 24 21:43:24 UTC 2014

Hey Paul,

This is by design, and reraising a single MechanismDriverError was really
to have a nice defined API for the MechanismManager class, avoid blanket
try/except calls in the caller. But I do agree that it's really annoying to
lose the information about the underlying exception. I like your idea of
including the original exception text in the MechanismDriverError message,
I think that'd help a lot.


On Fri, Jan 24, 2014 at 1:19 PM, Paul Ward <wpward at us.ibm.com> wrote:

> In implementing a mechanism driver for ML2 today, I discovered that any
> exceptions thrown from your mechanism driver will get swallowed by the ML2
> manager (
> https://github.com/openstack/neutron/blob/master/neutron/plugins/ml2/managers.py at
> line 164).
> Is this by design?  Sure, you can look at the logs, but it seems more user
> friendly to reraise the exception that got us here.  There could be
> multiple mechanism drivers being called in a chain, so changing this to
> reraise an exception that got us in trouble would really only be able to
> reraise the last exception encountered, but it seems that's better than
> none at all.  Or maybe even keep a list of exceptions raised and put all
> their texts into the MechanismDriverError message.
> Thoughts?
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