Applications that run on bare-metal clusters know precisely where they are running, the specification of the system, and their network information. This information helps them to work in a self-aware environment. For instance, these applications can align their resource usage, enhance their logs with more data, or send their node-related metric data. In the microservice architecture, applications are considered ephemeral with less dependency than the environment they are running on. However, self-awareness about runtime information, namely the introspective pattern, could increase the utility and discoverability of applications in distributed systems.

In Kubernetes, the Downward API ensures that the following environment and runtime data is provided for the pods:

• Environment: Node name, namespace, CPU, and memory limitations.
• Networking: Pod IP.
• Authorization: Service account.

In the following activity, a simple but self-aware Kubernetes application will be created and installed. The application has all of the runtime information, which is provided by Kubernetes as environment variables. Being a single application, it logs all of these variables to the console. However, the pod definition that's developed throughout this activity shows you how to use the Downward API inside containers to implement an introspective pattern in Kubernetes.