The ironic-conductor process will start, even if no drivers are loaded. Drivers may fail to load due to a misconfiguration, missing dependency, or other issues.
If no drivers are loaded, the conductor process can not function, and should shut down with a helpful error message.
Logs and simple way to reproduce:
$ grep enabled_drivers etc/ironic/ironic.conf.local
enabled_drivers=
$ ironic-conductor -v --config-file=etc/ironic/ironic.conf.local
2014-12-22 13:39:11.384 29092 INFO ironic.common.driver_factory [-] Loaded the following drivers: []
2014-12-22 13:39:11.589 29092 INFO ironic.conductor.manager [-] Successfuly started conductor with hostname zebra.
2014-12-22 13:39:11.601 29092 INFO oslo.messaging._drivers.impl_rabbit [-] Connecting to AMQP server on localhost:5672
2014-12-22 13:39:11.611 29092 INFO oslo.messaging._drivers.impl_rabbit [-] Connected to AMQP server on 127.0.0.1:5672
2014-12-22 13:39:11.618 29092 INFO ironic.common.service [-] Created RPC server for service ironic.conductor_manager on host zebra.
$ ironic driver-list
+---------------------+----------------+
| Supported driver(s) | Active host(s) |
+---------------------+----------------+
+---------------------+----------------+
I guess we are stopping conductor if any of the enabled driver's couldn't be loaded.
https:/
So this case is only when enabled_drivers is empty.