The tasks of an orchestrator

So, what are the tasks that we expect an orchestrator worth its money to execute for us? Let's look at them in detail. The following list shows the most important tasks that, at the time of writing, enterprise users typically expect from their orchestrator.

Reconciling the desired state

When using an orchestrator, one tells it in a declarative way how one wants it to run a given application or application service. We learned what declarative versus imperative means in Chapter 8, Docker Compose. Part of this declarative way of describing the application service we want to run is elements such as which container image to use, how many instances to run of this service, which ports to open, and more. This declaration of the properties of our application service is what we call the desired state.

So,  when we now tell the orchestrator the first time to create such a new application service based on the declaration, then the orchestrator makes sure to schedule as many...