Checking Properties of Resources in Stacks

Property-Check manages properties of each resource in stack as well as status of resources.
Property-check enables Heat to protect resources in stack against incorrect operations from other OpenStack components.

Now, heat doesn't manage each property of resources in stacks, so if user did an incorrect operation for resources a result of the operation for the resources remains forever.
Heat can't repair the change by itself.
And user can only restore the property by using OpenStack API except Heat API.

Managing properties of resources provides Heat an ability to detect changes for resources from other OpenStack API.
In other words, Heat will get an ability to check whether resources in stack have connection to other resource out of the stack or not.

=== usecase 1 ===
To detect a changed property by miss operation

 1. User creates a new stack containing OS::Neutron::Net with admin_state_up = False
 2. Using Neutron API or Horizon, the user changes the admin_state_up to True by mistake as another network.
 3. Heat detects the change and the user is aware of that.
 4. The user repairs the property using stack-repair or OpenStack API if the change is caused by incorrect operation

=== usecase 2 ===
To detect some resources relationship to an out of stacks resources

  1. Create a new stack consisting of OS::Nova::Server
  2. Create a new volume by Cinder API
  3. Connect between the vm instance in the stack and the volume which is out of stack
  4. Heat detects a resource-relationship between the vm and the volume
  5. Then, heat disconnects the relationship using stack repair or stack convergence