Expand-Contract Pattern applied in Rolling Upgrade Deployment

Technologies used

• Java 11
• Maven
• Quarkus framework
• Docker
• Kubernetes
• Jib
• HTML/CSS/JS
• Weave Scope visualisation & monitoring tool
• PostgreSQL
• Flyway

Techniques used

• Rolling Updates
• Expand/Contract pattern
• Evolutionary Database Design

Architecture

Packaging and running the example in a kubernetes cluster

1. Start minikube with the following addons:

minikube start --addons registry, ingress

2. Forward the image registry port:

kubectl port-forward --namespace kube-system registry-<id> 5000:5000

3. Run the deployment script:

./minikube-deploy.sh

4. Get ngnix IP from ADDRESS column using:

kubectl get ingress -n custom

5. Map customer.domain to the IP provided by step above to etc/hosts

6. Access the application on http://customer.domain

Expand/Contract demo explanation

Beside master branch you have 3 additional branches that represent 3 backward compatible database versions.

The problem:

You need to split name column into two separate columns, first name and last name and to maintain backward compatibility with the previous version.

Solution:

Migration version	Branch	State	What happens to the database?
V1.0	demo/v1_starting_state	Starting	Create a customer table that contains an ID and a name
V2.0	demo/v2_expand_state	Expand	Append first_name and last_name column. Bidirectional synchronization using triggers between name and (first_name, last_name)
V3.0	demo/v3_contract_state	Contract	After all clients migrated to V2.0, in this state you can remove the old column name and also the synchronization triggers.