Bug 1111520

Description of problem:
This problem occurs on all cluster in ovirt which do just contain
one single host (e.g. local storage)

when a logical network gets created, the default is to make it "required"
on the cluster it gets attached to.

if the single host inside the cluster is missing one logcial network

_all_ vms get fenced, because ovirt wants to restart them on another host
in the cluster, which has all required networks.

Version-Release number of selected component (if applicable):
latest master

How reproducible:
always

Steps to Reproduce:
1. create logical networks for each vm in a single node cluster
2. remove one of the networks from the host
3. watch all vms shutdown

Actual results:
all vms get fenced

Expected results:
here are some superior alternatives (which also can be combined):

a)fence just the vms which have the missing required networks attached
b) do no fencing at all, when just one host is up in the cluster, because
you can't restart the vms on a different host anyway. make sure _before_ you
fence vms that there is a suitable host which meets all requirements is available and has enough resources to run those fenced vms (this requires some computation!)
c) do not mark newly created logical networks as "required" by default, without
user interaction.

Additional info:
I doubt the infrastructure level is the correct point where you want to decide
what happens when a given network connection is not available.
ovirt does this decision by default in the following way:

if the (default)required network is not there, shutdown all vms and start them
on a different host.

this does make no sense, if vm "a" doesn't have this network attached to any of it's interfaces.

it does not even make sense if vm "b" has this network attached to it's interface, because you can't tell if this vm really "requires" this network
(it might have other networks attached, which may be enough for this vm).

Again: this is an application level problem, this means, it depends on the application inside the vm if a network outage is serious or not.

ovirt does not know anything about the application inside the vm, thus ovirt
can't make expectations about the importance of a vanished logical network.

there are 3 cases:

1. the app does not need networking at all
2.  the app can handle network failure itself (wait for network to come up again, logging, alarming etc.)
3. the app is poorly designed and crashes/does not work anymore

just in case 3. ovirt would be justified to do what it does by default.

In my opinion it would be up to the network/ovirt administrator to decide
this case and not make this a default for all cases.

I do not know if I selected the correct ovirt component, please reassign, if applicable.