[nailgun] Roles assignment validation doesn't work on server-side

[Ivan Kolodyazhny]

Roles assignment validation works only on Web UI. E.g. You aren't able to assign Compute+Controller roles to a one node, only one Controller could be added on simple mode (multinode mode).

UI adds nodes to a cluster using NodeCollectionHandler (/api/nodes/). It doesn't contain any kind of roles validation. Some of needed validation is in NodeAssignmentHandler, but I'm not sure that it is using now.

Steps to reproduce:
1. Create cluster in multinode mode.
2. Add 3 controllers using REST API or by hacking UI in firebug, etc
3. Start deployment.

Actual results:
Deployment started.

Expected results:
You shouldn't be able to add 3 controllers in simple mode or deployment should not start.

Tested on latest master (ISO & Fake UI)

[Evgeniy L (rustyrobot)]

Additional research is required, my opinion is we shouldn't set cluster and roles via '/api/nodes/' handler.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/87209

[Alexander Kislitsky (akislitsky)]

We have no restrictions on number of nodes in openstack.yaml. This issue should be blueprinted and designed as feature.

[Nikolay Markov (nmarkov)]

Proper language parser and validator for YAML-defined checks is needed on backend.

[Andriy Popovych (popovych-andrey)]

I think we can use limits mixin for it https://github.com/stackforge/fuel-web/blob/master/nailgun/nailgun/utils/restrictions.py

[Vladimir Sharshov (vsharshov)]

This is feature. It is need blueprint. Can be safely moving to 8.0