/startup endpoint

[nhoening]

This checks if the recently started container has all sub processes ready. I guess the difference from /readiness (#213) is that it considers a grace period since the startup time.

From a Kubernetes-bases article:

Startup probe. This is used when the container starts up, to indicate that it's ready. Once the startup probe succeeds, Kubernetes switches to using the liveness probe to determine if the application is alive. This probe was introduced in Kubernetes version 1.16.