Version B is slowly rolled out and replacing version A. Also known as rolling-update or incremental.
The ramped deployment strategy consists of slowly rolling out a version of an application by replacing instances one after the other until all the instances are rolled out. It usually follows the following process: with a pool of version A behind a load balancer, one instance of version B is deployed. When the service is ready to accept traffic, the instance is added to the pool. Then, one instance of version A is removed from the pool and shut down.
Depending on the system taking care of the ramped deployment, you can tweak the following parameters to increase the deployment time:
- Parallelism, max batch size: Number of concurrent instances to roll out.
- Max surge: How many instances to add in addition of the current amount.
- Max unavailable: Number of unavailable instances during the rolling update procedure.
- version 1 is serving traffic
- deploy version 2
- wait until all replicas are replaced with version 2
# Deploy the first application
$ kubectl apply -f app-v1.yaml
# Test if the deployment was successful
$ curl $(minikube service my-app --url)
2018-01-28T00:22:04+01:00 - Host: host-1, Version: v1.0.0
# To see the deployment in action, open a new terminal and run the following
# command
$ watch kubectl get po
# Then deploy version 2 of the application
$ kubectl apply -f app-v2.yaml
# Test the second deployment progress
$ service=$(minikube service my-app --url)
$ while sleep 0.1; do curl "$service"; done
# In case you discover some issue with the new version, you can undo the
# rollout
$ kubectl rollout undo deploy my-app
# If you can also pause the rollout if you want to run the application for a
# subset of users
$ kubectl rollout pause deploy my-app
# Then if you are satisfied with the result, resume rollout
$ kubectl rollout resume deploy my-app$ kubectl delete all -l app=my-app