POD DESIGN

POD DESIGN
----------



Labels and selectors : A standard method to group things together



apiVersion: apps/v1
kind: ReplicaSet
metadata:
  name: simple-webapp
  Labels:
    app: App1
    function: Front-end
spec:
  replicas: 3
  selector:
    matchLabels:
      app: App1
  template:
    metadata:
      labels:
        app: App1
        function: Front-end
    spec:
      containers:
      - name: simple-webapp
        image: simple-webapp

Annotations
---

apiVersion: apps/v1
kind: ReplicaSet
metadata:
  name: simple-webapp
  Labels:
    app: App1
    function: Front-end
  annotations:
    buildversion: 1.34
spec:
  replicas: 3
  selector:
    matchLabels:
      app: App1
  template:
    metadata:
      labels:
        app: App1
        function: Front-end
    spec:
      containers:
      - name: simple-webapp
        image: simple-webapp



Rolling Updates & Rollbacks
---



> kubectl rollout status deployment/myapp-deployment


> kubectl rollout history deployment/myapp-deployment


Two types of deployment strategies

1- Recreate strategy
2- Rolling Updates (default)



Having the following deployment

apiVersion: apps/v1
kind: Deployment
metadata:
  name: myapp-deployment
  labsl:
    app: myapp
    type: front-end
spec:
  template:
    metadata:
      name: myapp-pod
      labels:
        app: myapp
        type: front-end
    spec:
      containers:
      - name: nginx-container
        image: nginx:1.7.1
  replicas: 3
  selector:
    matchLabels:
      type: front-end


To rollback

> kubectl rollout undo deployment/myapp-deployment

To Update the deployment
> kubectl set image deployment/myapp-deployment nginx=nginx:1.9.1
> kubectl set image deployment/frontend simple-webapp=kodekloud/webapp-color:v2


JOBS
---

To create a job

job-definition.yaml
--
apiVersion: batch/v1
kind: Job
metadata:
  name: math-add-job
spec:
  completions: 3
  parallelism: 3
  template:
    spec:
      containers:
        - name: math-add-job
          image: ubuntu
          command: ['expr','3','+','4']
      restartPolicy: Never

> kubectl create -f pod-definition.yaml

> kubectl get jobs


CronJobs
----

job-definition.yaml
--
apiVersion: batch/v1beta1
kind: CronJob
metadata:
  name: reporting-cron-job
spec:
  schedule: "*/1 * * * *"
  jobTemplate:
    spec:
      completions: 3
      parallelism: 3
      template:
        spec:
          containers:
            - name: reporting-tool
              image: reporting-tool
          restartPolicy: Never


--- practice---


apiVersion: batch/v1
kind: Job
metadata:
  name: throw-dice-job
spec:
  template:
    spec:
      containers:
        - name: throw-dice
          image: kodekloud/throw-dice
      restartPolicy: Never


apiVersion: batch/v1beta1
kind: CronJob
metadata:
  name: throw-dice-cron-job
spec:
  schedule: "30 21 * * *"
  jobTemplate:
    spec:
      completions: 3
      parallelism: 3
      template:
        spec:
          containers:
            - name: throw-dice
            image: kodekloud/throw-dice
          restartPolicy: Never