What is a Pod ?

A Pod is the smallest unit allowing to run workload. It is a group of containers sharing a network stack and storage. The specification of a Pod is defined in an YAML file.

Example of a simple Pod’s specification:

The following specification defines a Pod which running a simple container based on the stefanprodan/podinfo image.

apiVersion: v1
kind: Pod
metadata:
  name: podinfo
spec:
  containers:
  - name: podinfo
    image: stefanprodan/podinfo

Many additional properties are needed for this Pod to run securely in a production environment, such as:

• resource definition to control the amount of RAM / CPU the containers can use
• readinessProbe to know when a container is ready to receive traffic
• livenessProbe to check the health of a container
• securityContext to control what the container’s process can and cannot do from a security perspective

Below is the example of a more production ready Pod’s specification:

apiVersion: v1
kind: Pod
metadata:
  name: podinfo
  labels:
    app: podinfo
spec:
  containers:
  - image: stefanprodan/podinfo:6.1.0
    name: podinfo
    resources:
      requests:
        cpu: 50m
        memory: 64Mi
      limits:
        cpu: 50m
        memory: 64Mi
    livenessProbe:
      httpGet:
        path: /healthz
        port: 9898
      initialDelaySeconds: 3
      periodSeconds: 3
    readinessProbe:
      httpGet:
        path: /readyz
        port: 9898
      initialDelaySeconds: 3
      periodSeconds: 3
    securityContext:
      allowPrivilegeEscalation: false
      readOnlyRootFilesystem: true
      runAsUser: 10000
      runAsNonRoot: true
      seccompProfile:
        type: RuntimeDefault
      capabilities:
        drop:
        - ALL
…

Base commands

• Creating a Pod using a specification

kubectl apply -f pod.yaml

• Creating a Pod using an imperative command

kubectl run podinfo --image=stefanprodan/podinfo

• Listing the existing Pods

kubectl get pods

• Getting a Pod’s details

kubectl get pods podinfo -o yaml

• Getting the main properties of a Pod

kubectl describe pod podinfo

• Getting the logs of a Pod’s container

kubectl logs podinfo

• Running an Interactive shell in a Pod’s container

kubectl exec -ti podinfo -- /bin/sh

• Deleting a Pod

kubectl delete pod podinfo

Running the VotingApp inside Pods

As presented above, the VotingApp is a microservice application with the following architecture

You will now run a Pod for each of the microservice