c.pod_design.md

Pod design (20%)

Labels and annotations

kubernetes.io > Documentation > Concepts > Overview > Labels and Selectors

Create 3 pods with names nginx1,nginx2,nginx3. All of them should have the label app=v1

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kubectl run nginx1 --image=nginx --restart=Never --labels=app=v1
kubectl run nginx2 --image=nginx --restart=Never --labels=app=v1
kubectl run nginx3 --image=nginx --restart=Never --labels=app=v1

Show all labels of the pods

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kubectl get po --show-labels

Change the labels of pod 'nginx2' to be app=v2

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kubectl label po nginx2 app=v2 --overwrite

Get the label 'app' for the pods

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kubectl get po -l app
# or
kubectl get po --label-columns=app

Get only the 'app=v2' pods

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kubectl get po -l app=v2
# or
kubectl get po -l 'app in (v2)'
# or
kubectl get po --selector=app=v2

Remove the 'app' label from the pods we created before

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kubectl label po nginx1 nginx2 nginx3 app-
# or
kubectl label po nginx{1..3} app-
# or
kubectl label po -l app app-

Create a pod that will be deployed to a Node that has the label 'accelerator=nvidia-tesla-p100'

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Add the label to a node:

kubectl label nodes <your-node-name> accelerator=nvidia-tesla-p100
kubectl get nodes --show-labels

We can use the 'nodeSelector' property on the Pod YAML:

apiVersion: v1
kind: Pod
metadata:
  name: cuda-test
spec:
  containers:
    - name: cuda-test
      image: "k8s.gcr.io/cuda-vector-add:v0.1"
  nodeSelector: # add this
    accelerator: nvidia-tesla-p100 # the selection label

You can easily find out where in the YAML it should be placed by:

kubectl explain po.spec

OR: Use node affinity (https://kubernetes.io/docs/tasks/configure-pod-container/assign-pods-nodes-using-node-affinity/#schedule-a-pod-using-required-node-affinity)

apiVersion: v1
kind: Pod
metadata:
  name: affinity-pod
spec:
  affinity:
    nodeAffinity:
      requiredDuringSchedulingIgnoredDuringExecution:
        nodeSelectorTerms:
        - matchExpressions:
          - key: accelerator
            operator: In
            values:
            - nvidia-tesla-p100
  containers:
    ...

Annotate pods nginx1, nginx2, nginx3 with "description='my description'" value

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kubectl annotate po nginx1 nginx2 nginx3 description='my description'

#or

kubectl annotate po nginx{1..3} description='my description'

Check the annotations for pod nginx1

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kubectl describe po nginx1 | grep -i 'annotations'

# or

kubectl get pods -o custom-columns=Name:metadata.name,ANNOTATIONS:metadata.annotations.description

As an alternative to using | grep you can use jsonPath like kubectl get po nginx1 -o jsonpath='{.metadata.annotations}{"\n"}'

Remove the annotations for these three pods

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kubectl annotate po nginx{1..3} description-

Remove these pods to have a clean state in your cluster

show

kubectl delete po nginx{1..3}

Deployments

kubernetes.io > Documentation > Concepts > Workloads > Controllers > Deployments

Create a deployment with image nginx:1.7.8, called nginx, having 2 replicas, defining port 80 as the port that this container exposes (don't create a service for this deployment)

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kubectl create deployment nginx  --image=nginx:1.7.8  --dry-run=client -o yaml > deploy.yaml
vi deploy.yaml
# change the replicas field from 1 to 2
# add this section to the container spec and save the deploy.yaml file
# ports:
#   - containerPort: 80
kubectl apply -f deploy.yaml

or, do something like:

kubectl create deployment nginx  --image=nginx:1.7.8  --dry-run=client -o yaml | sed 's/replicas: 1/replicas: 2/g'  | sed 's/image: nginx:1.7.8/image: nginx:1.7.8\n        ports:\n        - containerPort: 80/g' | kubectl apply -f -

View the YAML of this deployment

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kubectl get deploy nginx -o yaml

View the YAML of the replica set that was created by this deployment

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kubectl describe deploy nginx # you'll see the name of the replica set on the Events section and in the 'NewReplicaSet' property
# OR you can find rs directly by:
kubectl get rs -l run=nginx # if you created deployment by 'run' command
kubectl get rs -l app=nginx # if you created deployment by 'create' command
# you could also just do kubectl get rs
kubectl get rs nginx-7bf7478b77 -o yaml

Get the YAML for one of the pods

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kubectl get po # get all the pods
# OR you can find pods directly by:
kubectl get po -l run=nginx # if you created deployment by 'run' command
kubectl get po -l app=nginx # if you created deployment by 'create' command
kubectl get po nginx-7bf7478b77-gjzp8 -o yaml

Check how the deployment rollout is going

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kubectl rollout status deploy nginx

Update the nginx image to nginx:1.7.9

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kubectl set image deploy nginx nginx=nginx:1.7.9
# alternatively...
kubectl edit deploy nginx # change the .spec.template.spec.containers[0].image

The syntax of the 'kubectl set image' command is kubectl set image (-f FILENAME | TYPE NAME) CONTAINER_NAME_1=CONTAINER_IMAGE_1 ... CONTAINER_NAME_N=CONTAINER_IMAGE_N [options]

Check the rollout history and confirm that the replicas are OK

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kubectl rollout history deploy nginx
kubectl get deploy nginx
kubectl get rs # check that a new replica set has been created
kubectl get po

Undo the latest rollout and verify that new pods have the old image (nginx:1.7.8)

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kubectl rollout undo deploy nginx
# wait a bit
kubectl get po # select one 'Running' Pod
kubectl describe po nginx-5ff4457d65-nslcl | grep -i image # should be nginx:1.7.8

Do an on purpose update of the deployment with a wrong image nginx:1.91

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kubectl set image deploy nginx nginx=nginx:1.91
# or
kubectl edit deploy nginx
# change the image to nginx:1.91
# vim tip: type (without quotes) '/image' and Enter, to navigate quickly

Verify that something's wrong with the rollout

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kubectl rollout status deploy nginx
# or
kubectl get po # you'll see 'ErrImagePull'

Return the deployment to the second revision (number 2) and verify the image is nginx:1.7.9

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kubectl rollout undo deploy nginx --to-revision=2
kubectl describe deploy nginx | grep Image:
kubectl rollout status deploy nginx # Everything should be OK

Check the details of the fourth revision (number 4)

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kubectl rollout history deploy nginx --revision=4 # You'll also see the wrong image displayed here

Scale the deployment to 5 replicas

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kubectl scale deploy nginx --replicas=5
kubectl get po
kubectl describe deploy nginx

Autoscale the deployment, pods between 5 and 10, targetting CPU utilization at 80%

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kubectl autoscale deploy nginx --min=5 --max=10 --cpu-percent=80

Pause the rollout of the deployment

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kubectl rollout pause deploy nginx

Update the image to nginx:1.9.1 and check that there's nothing going on, since we paused the rollout

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kubectl set image deploy nginx nginx=nginx:1.9.1
# or
kubectl edit deploy nginx
# change the image to nginx:1.9.1
kubectl rollout history deploy nginx # no new revision

Resume the rollout and check that the nginx:1.9.1 image has been applied

show

kubectl rollout resume deploy nginx
kubectl rollout history deploy nginx
kubectl rollout history deploy nginx --revision=6 # insert the number of your latest revision

Delete the deployment and the horizontal pod autoscaler you created

show

kubectl delete deploy nginx
kubectl delete hpa nginx

#Or
kubectl delete deploy/nginx hpa/nginx

Jobs

Create a job with image perl that runs the command with arguments "perl -Mbignum=bpi -wle 'print bpi(2000)'"

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kubectl create job pi  --image=perl -- perl -Mbignum=bpi -wle 'print bpi(2000)'

Wait till it's done, get the output

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kubectl get jobs -w # wait till 'SUCCESSFUL' is 1 (will take some time, perl image might be big)
kubectl get po # get the pod name
kubectl logs pi-**** # get the pi numbers
kubectl delete job pi

Create a job with the image busybox that executes the command 'echo hello;sleep 30;echo world'

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kubectl create job busybox --image=busybox -- /bin/sh -c 'echo hello;sleep 30;echo world'

Follow the logs for the pod (you'll wait for 30 seconds)

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kubectl get po # find the job pod
kubectl logs busybox-ptx58 -f # follow the logs

See the status of the job, describe it and see the logs

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kubectl get jobs
kubectl describe jobs busybox
kubectl logs job/busybox

Delete the job

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kubectl delete job busybox

Create a job but ensure that it will be automatically terminated by kubernetes if it takes more than 30 seconds to execute

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kubectl create job busybox --image=busybox --dry-run=client -o yaml -- /bin/sh -c 'while true; do echo hello; sleep 10;done' > job.yaml
vi job.yaml

Add job.spec.activeDeadlineSeconds=30

apiVersion: batch/v1
kind: Job
metadata:
  creationTimestamp: null
  labels:
    run: busybox
  name: busybox
spec:
  activeDeadlineSeconds: 30 # add this line
  template:
    metadata:
      creationTimestamp: null
      labels:
        run: busybox
    spec:
      containers:
      - args:
        - /bin/sh
        - -c
        - while true; do echo hello; sleep 10;done
        image: busybox
        name: busybox
        resources: {}
      restartPolicy: OnFailure
status: {}

Create the same job, make it run 5 times, one after the other. Verify its status and delete it

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kubectl create job busybox --image=busybox --dry-run=client -o yaml -- /bin/sh -c 'echo hello;sleep 30;echo world' > job.yaml
vi job.yaml

Add job.spec.completions=5

apiVersion: batch/v1
kind: Job
metadata:
  creationTimestamp: null
  labels:
    run: busybox
  name: busybox
spec:
  completions: 5 # add this line
  template:
    metadata:
      creationTimestamp: null
      labels:
        run: busybox
    spec:
      containers:
      - args:
        - /bin/sh
        - -c
        - echo hello;sleep 30;echo world
        image: busybox
        name: busybox
        resources: {}
      restartPolicy: OnFailure
status: {}

kubectl create -f job.yaml

Verify that it has been completed:

kubectl get job busybox -w # will take two and a half minutes
kubectl delete jobs busybox

Create the same job, but make it run 5 parallel times

show

vi job.yaml

Add job.spec.parallelism=5

apiVersion: batch/v1
kind: Job
metadata:
  creationTimestamp: null
  labels:
    run: busybox
  name: busybox
spec:
  parallelism: 5 # add this line
  template:
    metadata:
      creationTimestamp: null
      labels:
        run: busybox
    spec:
      containers:
      - args:
        - /bin/sh
        - -c
        - echo hello;sleep 30;echo world
        image: busybox
        name: busybox
        resources: {}
      restartPolicy: OnFailure
status: {}

kubectl create -f job.yaml
kubectl get jobs

It will take some time for the parallel jobs to finish (>= 30 seconds)

kubectl delete job busybox

Cron jobs

kubernetes.io > Documentation > Tasks > Run Jobs > Running Automated Tasks with a CronJob

Create a cron job with image busybox that runs on a schedule of "*/1 * * * *" and writes 'date; echo Hello from the Kubernetes cluster' to standard output

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kubectl create cronjob busybox --image=busybox --schedule="*/1 * * * *" -- /bin/sh -c 'date; echo Hello from the Kubernetes cluster'

See its logs and delete it

show

kubectl get cj
kubectl get jobs --watch
kubectl get po --show-labels # observe that the pods have a label that mentions their 'parent' job
kubectl logs busybox-1529745840-m867r
# Bear in mind that Kubernetes will run a new job/pod for each new cron job
kubectl delete cj busybox

Create a cron job with image busybox that runs every minute and writes 'date; echo Hello from the Kubernetes cluster' to standard output. The cron job should be terminated if it takes more than 17 seconds to start execution after its schedule.

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kubectl create cronjob time-limited-job --image=busybox --restart=Never --dry-run=client --schedule="* * * * *" -o yaml -- /bin/sh -c 'date; echo Hello from the Kubernetes cluster' > time-limited-job.yaml
vi time-limited-job.yaml

Add job.spec.activeDeadlineSeconds=17

apiVersion: batch/v1beta1
kind: CronJob
metadata:
  creationTimestamp: null
  name: time-limited-job
spec:
  startingDeadlineSeconds: 17 # add this line
  jobTemplate:
    metadata:
      creationTimestamp: null
      name: time-limited-job
    spec:
      template:
        metadata:
          creationTimestamp: null
        spec:
          containers:
          - args:
            - /bin/sh
            - -c
            - date; echo Hello from the Kubernetes cluster
            image: busybox
            name: time-limited-job
            resources: {}
          restartPolicy: Never
  schedule: '* * * * *'
status: {}