Comment 10 for bug 2031482

Hi all, I've been reviewing the possible causes for this error and I've noticed logs like these in the syslog for some machines (see for example logs on comment #6):

IP address [146.118.58.161] subnet 146.118.58.0/23: VLAN updated (vlan=5001)

This log comes from this function in src/maasserver/models/signals/interfaces.py:

def interface_vlan_update(instance, old_values, **kwargs):
 """When an interfaces VLAN is changed we need to do the following.

 * If its a controller move all assigned subnets to the new VLAN. This
   is done because the subnets defined are discovered on the
   controller and an administrator cannot change them.
 * If its a machine or device then we need to remove all links if the
   VLAN is different.
 """

This function has two different behaviors if the node is a controller or not but this log line:

log.msg(
   "%s: IP address [%s] subnet %s: "
   "VLAN updated (vlan=%s)." ...

Only occurs on the controller path and we are seeing it in non-controller machines. To separate these two cases there is this if line:

if not node.is_commissioning():

Which supposedly indicates that the node is a controller in case it is true. It is not intuitive that not is_commissioning equals that the node is a controller so it is possible that this not always works and thus sometimes the code path for controller is being taken for non-controller nodes.