Cloud Run Blue/Green Deployments

Google Cloud services which we will be using

• Artifact Registry
• Cloud Run

Our simple microservice contains a cat endpoint, which returns a random cat name in the below format

Artifact Registry

Create a repository in the Artifact Registry.

gcloud artifacts repositories create blue-green --location=us-central1 --repository-format=docker --description="Docker repository"

Once the repository is created, run the setup instructions on your machine. The setup instructions are available in the console, this command will change based on the region that you select during the repository creation.

gcloud auth configure-docker us-central1-docker.pkg.dev

Build and push the Docker image to Artifact Registry

Below commands are used to build and push the container image to the repository that we created in Artifact Registry

docker build -t cat-service-blue .
docker tag cat-service-blue us-central1-docker.pkg.dev/core-demos/blue-green/cat-service:blue
docker push us-central1-docker.pkg.dev/core-demos/blue-green/cat-service:blue

Cloud Run

Run the below gcloud command to run our cat-service on Cloud Run using the image that we pushed to Artifact Registry,

gcloud run deploy cat-service --image=us-central1-docker.pkg.dev/core-demos/blue-green/cat-service:blue --tag=blue --region=us-central1 --allow-unauthenticated

We can view our cat-service in the console,

Access the url of the cat-service and test the /cat endpoint

https://cat-service-u7xvbpiada-uc.a.run.app/cat endpoint is working fine, and is using the image with blue tag

Gradual rollout and traffic migration

Now, lets update the service(the response) and run it on Cloud Run

vim index.js

Replace blue with green in the code

Lets push this new change to to Artifact Registry

docker build -t cat-service-green .
docker tag cat-service-green us-central1-docker.pkg.dev/core-demos/blue-green/cat-service:green
docker push us-central1-docker.pkg.dev/core-demos/blue-green/cat-service:green

Now, lets run this new change(image with green tag) of our cat-service on Cloud Run and instruct Cloud Run not to migrate the traffic to this new revision/version using the “no-traffic” flag

gcloud run deploy cat-service --image=us-central1-docker.pkg.dev/core-demos/blue-green/cat-service:green --no-traffic --tag=green --region=us-central1 --allow-unauthenticated

CloudRun will generate a separate url for the new revision. That URL can be used for testing the new service with zero live traffic

We can get this URL from the console as well and you can see in the console that this new revision is not serving any traffic ( Traffic 0%)

We can validate this revision and If we are happy with our new revision, we can gradually migrate traffic to our new revision using this command (here I have given 50, which means 50% of the traffic will hit the new revision(green) and 50% will hit the blue).

gcloud run services update-traffic cat-service --to-tags green=50 --region=us-central1

Now, when we access our cat-service URL we get 50% blue responses and 50% green

We can keep increasing the traffic flowing to our new revision and once we are happy with it, we can set to 100%

gcloud run services update-traffic cat-service --to-tags green=100 --region=us-central1

Rollback

We can rollback at anytime If we find an issue with our new revision, we can rollback to the previous revision(one with blue tag) using this command

gcloud run services update-traffic cat-service --to-revisions cat-service-00001-wim=100 --region=us-central1