Kubernetes Probes: Startup, Liveness, Readiness

by Levent Ogut

Kubernetes has been disruptive due to the scalability, velocity, portability, and observability it adds to cloud deployments. While it brings a whole ecosystem of great features and options and eases complex deployment, it also has its own challenges. One of the great features Kubernetes has brought us is that of high availability. There are many high availability options in Kubernetes; in this article, we will discuss high availability options used for the application/microservice itself.

Pods — the smallest deployable units in Kubernetes — are scheduled once the declarative configuration is applied. Kube-scheduler is responsible for the calculation and schedule; once the schedule is accepted, it is in a controlled and calculated environment, and it is deemed service ready or not by the pod conditions. Using startup, readiness, and liveness probes, we can control when a pod should be deemed started, ready for service, or live. We will explore these conditions and triggers.

Pod and Container Status

Pods have phases and conditions; containers have states. These status properties can and will…