Application layer

The application layer, often referred to as the service fabric or orchestration layer, does all of the fun things we've come to value so highly in Kubernetes: basic deployment and routing, service discovery, load balancing, and self-healing. In order for a cluster operator to manage the life cycle of the cluster, these primitives must be present and functional in this layer. Most containerized applications will depend on the full functionality of this layer, and will interact with these functions in order to provide "orchestration" of the application across multiple cluster hosts. When an application scales up or changes a configuration setting, the application layer will be managed by this layer. The application layer cares about the desired state of the cluster, the application composition, service discovery, load balancing, and routing, and utilizes all of these pieces to keep data flowing from the correct point A to the correct point B.