¶ 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
show
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
# or
for i in `seq 1 3`; do k run nginx$i --image=nginx -l app=v1 ; done
¶ Show all labels of the pods
show
kubectl get po --show-labels
¶ Change the labels of pod 'nginx2' to be app=v2
show
kubectl label po nginx2 app=v2 --overwrite
¶ Get the label 'app' for the pods (show a column with APP labels)
show
kubectl get po -L app
# or
kubectl get po --label-columns=app
¶ Get only the 'app=v2' pods
show
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
show
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'
show
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
show
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
show
kubectl describe po nginx1 | grep -i 'annotations'
# or
kubectl get po nginx1 -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
show
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:1.18.0, called nginx, having 2 replicas, defining port 80 as the port that this container exposes (don't create a service for this deployment)
show
kubectl create deployment nginx --image=nginx:1.18.0 --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:1.18.0 --dry-run=client -o yaml | sed 's/replicas: 1/replicas: 2/g' | sed 's/image: nginx:1.18.0/image: nginx:1.18.0\n ports:\n - containerPort: 80/g' | kubectl apply -f -
or,
kubectl create deploy nginx --image=nginx:1.18.0 --replicas=2 --port=80
¶ View the YAML of this deployment
show
kubectl get deploy nginx -o yaml
¶ View the YAML of the replica set that was created by this deployment
show
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
show
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
show
kubectl rollout status deploy nginx
¶ Update the nginx image to nginx:1.19.8
show
kubectl set image deploy nginx nginx=nginx:1.19.8
# 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
show
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:1.18.0)
show
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:1.18.0
¶ Do an on purpose update of the deployment with a wrong image nginx:1.91
show
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
show
kubectl rollout status deploy nginx
# or
kubectl get po # you'll see 'ErrImagePull' or 'ImagePullBackOff'
¶ Return the deployment to the second revision (number 2) and verify the image is nginx:1.19.8
show
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)
show
kubectl rollout history deploy nginx --revision=4 # You'll also see the wrong image displayed here
¶ Scale the deployment to 5 replicas
show
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%
show
kubectl autoscale deploy nginx --min=5 --max=10 --cpu-percent=80
¶ Pause the rollout of the deployment
show
kubectl rollout pause deploy nginx
¶ Update the image to nginx:1.19.9 and check that there's nothing going on, since we paused the rollout
show
kubectl set image deploy nginx nginx=nginx:1.19.9
# or
kubectl edit deploy nginx
# change the image to nginx:1.19.9
kubectl rollout history deploy nginx # no new revision
¶ Resume the rollout and check that the nginx:1.19.9 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 named pi with image perl that runs the command with arguments "perl -Mbignum=bpi -wle 'print bpi(2000)'"
show
kubectl create job pi --image=perl -- perl -Mbignum=bpi -wle 'print bpi(2000)'
¶ Wait till it's done, get the output
show
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
OR
kubectl get jobs -w # wait till 'SUCCESSFUL' is 1 (will take some time, perl image might be big)
kubectl logs job/pi
kubectl delete job pi
¶ Create a job with the image busybox that executes the command 'echo hello;sleep 30;echo world'
show
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)
show
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
show
kubectl get jobs
kubectl describe jobs busybox
kubectl logs job/busybox
¶ Delete the job
show
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
show
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
show
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
show
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.
show
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 cronjob.spec.jobTemplate.spec.activeDeadlineSeconds=17
apiVersion: batch/v1beta1
kind: CronJob
metadata:
creationTimestamp: null
name: time-limited-job
spec:
jobTemplate:
metadata:
creationTimestamp: null
name: time-limited-job
spec:
activeDeadlineSeconds: 17 # add this line
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: {}