To update an existing deployment, you can use the kubectl edit command. Simply update the image attribute for your containers and save the Deployment. The deployment will automatically create new pods with the new image you specified, and terminate pods using the old image in a controlled fashion.
Run the kubectl command to modify the tag of the container image. Run the kubectl edit command to edit the pod and modify the tag of the container image. Open the nginx. yaml configuration file of the pod, modify the tag of the container image, and then run the kubectl apply command to redeploy the pod.
If the image is tagged latest, then Kubernetes will assume the imagePullPolicyto be Always. An image with no tag is assumed to be latest, and so its policy is set to Always.
You can configure your pod with a grace period (for example 30 seconds or more, depending on container startup time and image size) and set "imagePullPolicy: "Always"
. And use kubectl delete pod pod_name
.
A new container will be created and the latest image automatically downloaded, then the old container terminated.
Example:
spec:
terminationGracePeriodSeconds: 30
containers:
- name: my_container
image: my_image:latest
imagePullPolicy: "Always"
I'm currently using Jenkins for automated builds and image tagging and it looks something like this:
kubectl --user="kube-user" --server="https://kubemaster.example.com" --token=$ACCESS_TOKEN set image deployment/my-deployment mycontainer=myimage:"$BUILD_NUMBER-$SHORT_GIT_COMMIT"
Another trick is to intially run:
kubectl set image deployment/my-deployment mycontainer=myimage:latest
and then:
kubectl set image deployment/my-deployment mycontainer=myimage
It will actually be triggering the rolling-update but be sure you have also imagePullPolicy: "Always"
set.
Update:
another trick I found, where you don't have to change the image name, is to change the value of a field that will trigger a rolling update, like terminationGracePeriodSeconds
. You can do this using kubectl edit deployment your_deployment
or kubectl apply -f your_deployment.yaml
or using a patch like this:
kubectl patch deployment your_deployment -p \
'{"spec":{"template":{"spec":{"terminationGracePeriodSeconds":31}}}}'
Just make sure you always change the number value.
UPDATE 2019-06-24
Based on the @Jodiug comment if you have a 1.15
version you can use the command:
kubectl rollout restart deployment/demo
Read more on the issue:
https://github.com/kubernetes/kubernetes/issues/13488
Well there is an interesting discussion about this subject on the kubernetes GitHub project. See the issue: https://github.com/kubernetes/kubernetes/issues/33664
From the solutions described there, I would suggest one of two.
1.Prepare deployment
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
name: demo
spec:
replicas: 1
template:
metadata:
labels:
app: demo
spec:
containers:
- name: demo
image: registry.example.com/apps/demo:master
imagePullPolicy: Always
env:
- name: FOR_GODS_SAKE_PLEASE_REDEPLOY
value: 'THIS_STRING_IS_REPLACED_DURING_BUILD'
2.Deploy
sed -ie "s/THIS_STRING_IS_REPLACED_DURING_BUILD/$(date)/g" deployment.yml
kubectl apply -f deployment.yml
kubectl patch deployment web -p \
"{\"spec\":{\"template\":{\"metadata\":{\"labels\":{\"date\":\"`date +'%s'`\"}}}}}"
Of course the imagePullPolicy: Always
is required on both cases.
kubectl rollout restart deployment myapp
This is the current way to trigger a rolling update and leave the old replica sets in place for other operations provided by kubectl rollout
like rollbacks.
I use Gitlab-CI to build the image and then deploy it directly to GCK. If use a neat little trick to achieve a rolling update without changing any real settings of the container, which is changing a label to the current commit-short-sha.
My command looks like this:
kubectl patch deployment my-deployment -p "{\"spec\":{\"template\":{\"metadata\":{\"labels\":{\"build\":\"$CI_COMMIT_SHORT_SHA\"}}}}}}"
Where you can use any name and any value for the label as long as it changes with each build.
Have fun!
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