MAAS returns HTTP/500 when adding a second managed interface to cluster controller

[Eduardo Damato]

1. Description of the problem:

Adding a second managed interface to a MAAS cluster controller is forbidden by design but permitted by interface.

2. Ubuntu release, software version, Release Number and Architecture of the selected components.

12.04.3 LTS

ii maas 1.2+bzr1373+dfsg-0ubuntu1~12.04.2 Ubuntu MAAS Server
ii maas-cli 1.2+bzr1373+dfsg-0ubuntu1~12.04.2 Ubuntu MAAS Client Tool
ii maas-cluster-controller 1.2+bzr1373+dfsg-0ubuntu1~12.04.2 Ubuntu MAAS Cluster Controller
ii maas-common 1.2+bzr1373+dfsg-0ubuntu1~12.04.2 Ubuntu MAAS Server
ii maas-region-controller 1.2+bzr1373+dfsg-0ubuntu1~12.04.2 Ubuntu MAAS Server
ii python-django-maas 1.2+bzr1373+dfsg-0ubuntu1~12.04.2 Ubuntu MAAS Server - (django files)
ii python-maas-client 1.2+bzr1373+dfsg-0ubuntu1~12.04.2 Ubuntu MAAS API Client - (python files)
ii python-maas-provisioningserver 1.2+bzr1373+dfsg-0ubuntu1~12.04.2 Ubuntu MAAS Server

3. How reproducible is the problem?

every time

4. Steps to Reproduce:

4.1. Go on WebUI and click on the gears
4.2. Click on edit the cluster controller
4.3. Check that there is a managed interface
4.3. Click on add interface
4.4. Fill in all the details and choose managed interface
4.5. Click on save

 a. Actual Results: HTTP error 500
 b. Expected Results: MAAS UI not allow such configuration if it goes against the design/implementation.

5. Known Workaround:

None atm

6. Additional information:

Trace from maas log showing that validation failed:

ERROR 2013-10-03 18:15:49,465 django.request Internal Server Error: /MAAS/clusters/d4262a5f-5d0c-4dbb-9144-dc3398ac8035/interfaces/add/
Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/django/core/handlers/base.py", line 111, in get_response
    response = callback(request, *callback_args, **callback_kwargs)
  File "/usr/lib/python2.7/dist-packages/django/contrib/auth/decorators.py", line 23, in _wrapped_view
    return view_func(request, *args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/django/views/generic/base.py", line 47, in view
    return self.dispatch(request, *args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/django/views/generic/base.py", line 68, in dispatch
    return handler(request, *args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/django/views/generic/edit.py", line 172, in post
    return super(BaseCreateView, self).post(request, *args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/django/views/generic/edit.py", line 138, in post
    return self.form_valid(form)
  File "/usr/lib/python2.7/dist-packages/maasserver/views/settings_clusters.py", line 134, in form_valid
    self.object = form.save(nodegroup=self.get_nodegroup())
  File "/usr/lib/python2.7/dist-packages/maasserver/forms.py", line 720, in save
    interface.save(*args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/maasserver/models/cleansave.py", line 35, in save
    self.full_clean()
  File "/usr/lib/python2.7/dist-packages/django/db/models/base.py", line 828, in full_clean
    raise ValidationError(errors)
ValidationError: {u'management': [u'Another managed interface already exists for this cluster.']}