Description of problem: If you create a network as non-required, you should be unable to choose it as a display network for your cluster Version-Release number of selected component (if applicable): How reproducible: Always Steps to Reproduce: 1. Create network as non-required 2. Choose this network as display network in Cluster/manage networks tab 3. Actual results: An action succeeds Expected results: An action should fail, it should succeed only when you change the network to be required Additional info:
It cannot be said categorically that the display network of a VM is more important than its VM network. If you are running a multi-vm DB server, and you need to spawn a new instance to serve a surge in requirement, you care much less about the display network of the VM. If there's a host lacks the display network, but has all functionally-required networks, the VM should start up there. Let us not nanny the user. If he declared the network as non-required, he probably means just that - it's nice to have the network in his use case, but it's not the end of the world if it's not there.
While I agree that in the long term we should allow running VMs without a display network, I'm unaware of such an RFE and currently the display network behaves de-facto as a required network, so we might as well reflect that in the GUI and in the engine.
If a non-required network looses its connectivity, VMs that have vNICs connected to it looses their network. But nothing horrible happens; the host is still oprational, and VMs do not migrate away, since the admin defined it as non-required. Same logic applies, and should continue to apply, when the network is connected to the virtual video device instead of a vNIC. VMs would loose their display for a while, but it's no big deal since the admin explicitly said so. Note that we cannot (and should not) start a VM if its display network does not have an IP on that host (bug 955429). Headless VMs (lacking video card) are cool, but not immediately related to this (not)bug.
Dan has made a very good point; my statement that display network behaves de-facto as a required network was inaccurate. A difference in behavior would be in the case of a display NIC going down while VMs are running on the host - if the network is required the VMs will be migrated away, while if it isn't they'll keep running. This is a strong enough case to allow for a non-required display network.