Putting it all together
We now have a toolset for running applications on Kubernetes. Let's look at a real-world example to see how this could all be combined to run an application with multiple tiers and functionality spread across Kubernetes resources:
Figure 4.4 – Multi-tier application diagram
As you can see, our diagrammed application contains a web tier running a .NET Framework application, a mid-tier or service tier running Java, a database tier running Postgres, and finally a logging/monitoring tier.
Our controller choices for each of these tiers are dependent on the applications we plan to run on each tier. For both the web tier and the mid-tier, we're running stateless applications and services, so we can effectively use Deployments to handle rolling out updates, blue/green deploys, and more.
For the database tier, we need our database cluster to know which Pod is a replica and which is a master – so we use a StatefulSet...
