3.2.3 Adding/Removing Resources
When adding resources, identify whether they are new or existing resources and what must be done with the resources.
3.2.3.1. Adding Resources
In the fixed scaling model, the same type of resource is always added to the service,
such as additional web servers.
This information can be a configuration parameter to the orchestration workflow that is set in advance by the administrator.
In the scale everything model, it is the application itself that scales
out, and it
requires
the location of the application in the service catalog from which it is derived.
With intelligent scaling, the localization process
identifies
the resource to be scaled and passes
that information to the orchestration workflow to scale that component. Depending on the application requirements, the scaling workflow might be generic enough to address all components of the application as a single workflow responsible for the scaling execution.
Due to the application complexities at each layer (web, business logic, data), a separate workflow is developed for scaling each component of the service and addressing the configuration.
3.2.3.2. Connectivity
To use the newly added resources the peripheral networking components must be configured. When auto-scaling a service, the consumption of the new resources should be transparent to the user. For this reason, it is required that access pathways be automatically updated with the appropriate configuration changes so that resources can be consumed.
Configuration updates might be required for the following:
Local load balancing.
Global load balancing.
Firewalls.
Authentication.
VPN gateways.