Probes - Allow you to customize how Kubernetes determines the status of your containers
Indicates whether the container is running properly, and governs whether the cluster will automatically stop or restart the container. Liveness probes can be created by including them in the container spec. This probe runs a command to test the container’s liveness.
apiVersion: v1
kind: Pod
metadata:
name: my-liveness-pod
spec:
containers:
- name: myapp-container
image: busybox
command: ['sh', '-c', "echo Hello, Kubernetes! && sleep 3600"]
livenessProbe:
exec:
command:
- echo
- testing
initialDelaySeconds: 5
periodSeconds: 5
Indicates whether the container is ready to service requests, and governs whether request will be forwarded to the pod.
Liveness and readiness probes can determine container status by doing things like running a command or making an http request
apiVersion: v1
kind: Pod
metadata:
name: my-readiness-pod
spec:
containers:
- name: myapp-container
image: nginx
readinessProbe:
httpGet:
path: /
port: 80
initialDelaySeconds: 5
periodSeconds: 5
A container’s normal console output goes into the container log. You can access container logs using the kubectl logs command. For example, create a pod that generates some output every second:
apiVersion: v1
kind: Pod
metadata:
name: counter
spec:
containers:
- name: count
image: busybox
args: [/bin/sh, -c, 'i=0; while true; do echo "$i: $(date)"; i=$((i+1)); sleep 1; done']
If a pod has more than one container, you must specify which container to get logs from using the -c flag.
kubectl logs my-pod -c my-container
The Kubernetes metrics server provides an API which allows you to access data about your pods, and nodes, such as CPU and memory usage.
cd ~/
git clone https://github.com/linuxacademy/metrics-server
kubectl apply -f ~/metrics-server/deploy/1.8+/
Verify
kubectl get --raw /apis/metrics.k8s.io/
With a working metrics server, you can use the kubectl top to gather information about resource usage within the cluster.
kubectl top pods
kubectl top pod resource-consumer-big
kubectl top pods -n kube-system
kubectl top nodes
Problems will occur in any system, and Kubernetes provides some great tools to help locate and fix problems when they occur within a cluster. Helpful resources: