Roles and groups in granular deployment is a different entities

[Stanislaw Bogatkin]

In a task-based deployment 'roles' and 'groups' entities is the same. But in granular (role) deployment they are completely different. It leads us to bugs like this: [0]. There is need to make them equal like in task-based deployment.

[0]: https://bugs.launchpad.net/fuel/+bug/1553049

[Ilya Kutukov (ikutukov)]

Here is a deployment graph from TestBlockDeviceDevicesSerialization80 with extended edges colouring.

When we calling _update_dependencies of OrchestratorGraph it is using groups to create dependancies.

If we are supposing that developer have made a mistake and defined roles instead of groups (see refer. bug) we should use roles as groups if no groups provided.

The green connections is the connections created using groups fields.
The red connections created using roles when groups are not found.

As you could see adding red lines (roles) creating loops in this graph making it's proper traversal impossible.

So i don't see easy way of substitution groups dependencies with roles in legacy orchestrator.

[Alexey Shtokolov (ashtokolov)]

We are going to deprecate role-based deployment for >=9.0 clusters. So I suggest to downgrade this bug to medium due to major changes in legacy code.