Worker Replicas and CPU count in Cluster

[strangiato]

With the instructions it may be helpful to talk about how many resources are needed in the environment.

Adding a check to the bootstrap script for how many CPUs / Memory are required has been on my todo list but that would be something useful to talk about in the course as well.

For the AWS Open Environment I usually recommend having a minimum 2 4xlarge nodes. Users will need to manually scale the MachineSet for this.

The default for the regular environment is usually fine since it provisions 3 workers by default.

At some point we could even include the cluster sizing calculator in the course once that is in a better state.