Kubernetes provides three layers of health checking. First, in the form of HTTP or TCP checks, K8s can attempt to connect to a particular endpoint and give a status of healthy on a successful connection. Second, application-specific health checks can be performed using command-line scripts. We can also use the exec container to run a health check from within your container. Anything that exits with a 0 status will be considered healthy.
Let's take a look at a few health checks in action. First, we'll create a new controller named nodejs-health-controller.yaml with a health check:
apiVersion: v1
kind: ReplicationController
metadata:
name: node-js
labels:
name: node-js
spec:
replicas: 3
selector:
name: node-js
template:
metadata:
labels:
name: node-js
spec:
containers:
- name: node-js
image...
