Tacker's Devstack script silently override configuration

[Mathieu Goessens]

Hi,

With devstack, users can configure some Neutron features with configuration variables, like Q_ML2_PLUGIN_*_TYPE_OPTIONS, Q_ML2_PLUGIN_EXT_DRIVERS, NEUTRON_PORT_SECURITY, OVS_BRIDGE_MAPPINGS etc.

However, Tacker' Devstack script silently override some of them in :
https://github.com/openstack/tacker/blob/master/devstack/lib/tacker#L216
(as of c23f81cd762d8bad1337b993265cd6b50ca17f4c).

Thus, a user who would use those configuration variables would not see its changes applied.

It could be better to add the Tacker specific configuration to those variables, and let devstack handle them.

Meanwhile, as a workaround, users can use post-config hooks to force their configuration, for example, adding the following lines to their locaf.conf would perform something similar than configuring OVS_BRIDGE_MAPPINGS :

[[post-config|/$Q_PLUGIN_CONF_FILE]]

[ovs]
bridge_mappings = public:br-ex,mgmtphysnet0:br-mgmt0,physnet42:br-net42

[Mathieu Goessens (gebura)]

A way to solve this bug would maybe be to add the relevant configuration to those overridden settings in https://github.com/openstack/tacker/blob/master/devstack/settings, for example by specifying OVS_BRIDGE_MAPPINGS+=$MGMT_PHYS_NET:$BR_MGMT and so on.

That way the user provided configuration may be preserved, and the code may be simplified, for example leveraging NEUTRON_CREATE_INITIAL_NETWORKS etc to create the bridges, allocate the IP to the interface etc.