[TC_26] NebulOuS scales up and down applications to comply with SLO

[Christos-Alexandros Sarros]

Objective:
Test if NebulOuS can detect that the SLO for an application component that allows scaling up is not being met and deploys new instances of the component.

Preconditions:
1. NebulOuS core is running.
2. Three NebulOuS nodes are active and registered in NebulOuS.
3. Application of “Scaling APP” is registered in NebulOuS. The APP SLO is configured such as max_age can’t be bigger than 30 seconds. Number of worker component instances can range from 0 to infinite. The objective function is set to minimize the number of instances of worker component.

Steps:

Step 1.
- Action: User logs in into NebulOuS web UI and launches an instance of the application “Scaling APP”.
- Expected result: NebulOuS deploys an instance of the APP component “controller”. No instance of worker component is created.

Step 2.
- Action: User interacts with the REST API offered by the controller component and sends a new job with a value of t = 30
- Expected result: After 30 seconds, NebulOuS detects that the SLO of the application has been violated and creates a new instance of worker component.

Step 3.
- Action: User interacts with the REST API offered by the controller component and sends 3 new jobs with a value of t = 30
- Expected result: After 30 seconds, NebulOuS detects that the SLO of the application has been violated and creates a new instance of worker component. This happens 2 times more without the user interacting with the APP.

Step 4.
- Action: None
- Expected result: All requests are completed and associated worker components terminated. Resources are freed.