Implementing Blue/Green Deployments with Kubernetes and Istio: A Comprehensive Guide

Last updated on June 30, 2023

While Blue/Green deployments may be a popular strategy for achieving zero-downtime deployments that reduce the risk of introducing new application versions, but sadly it ain’t easy to find good quality tutorials, examples and documentation covering this topic online. Whole field of work and related technologies themselves are simply evolving too quickly so it will take some time for open-source community to catch up and publish tutorials and howtos of good quality. For this reason, in this tutorial we will try to fill this gap a little and explain the process of setting up Blue/Green deployments using Kubernetes and Istio, and will hopefully bring you closer to understanding how to deploy your applications while avoiding dreadful downtimes. Keep in mind that this is just generalized walk-trough which explains the process, not step by step tutorial you can follow – having solid understanding of kubernetes, and systems & networks in general is still necessary if you want to achieve this in practice.

Prerequisites

1. Basic understanding of Kubernetes, Istio, and DevOps concepts.
2. Access to a Kubernetes cluster (version 1.19 or later).
3. Istio installed on your Kubernetes cluster (version 1.10 or later).
4. `kubectl` and `istioctl` command-line tools installed on your local machine.

Step 1: Preparing your application

1. Ensure that your application is containerized and has a corresponding Docker image.
2. Make sure your application supports graceful shutdowns to allow for seamless switching between versions.

Step 2: Deploying your application to Kubernetes

1. Create a Kubernetes namespace for your application.
2. Create a Kubernetes deployment for your application, with at least two replicas for redundancy.
3. Create a Kubernetes service to expose your application internally within the cluster.
4. Apply the configuration files using `kubectl apply`.

Step 3: Setting up Istio for Blue/Green deployments

1. Label the namespace you created earlier with `istio-injection=enabled`.
2. Create an Istio `Gateway` resource to expose your application externally.
3. Create an Istio `VirtualService` resource that routes traffic to your application’s Kubernetes service.
4. Apply the Istio configuration files using `kubectl apply`.

Step 4: Deploying a new version of your application

1. Update your application’s Docker image and push it to a container registry.
2. Update your Kubernetes deployment configuration to use the new Docker image.
3. Apply the updated configuration using `kubectl apply`.
4. Verify that the new version of your application is running alongside the old version.

Step 5: Switching traffic to the new version

1. Update the Istio `VirtualService` configuration to route traffic to the new version of your application.
2. Apply the updated configuration using `kubectl apply`.
3. Verify that traffic is being routed to the new version by monitoring your application’s logs or metrics.

Step 6: Rolling back in case of issues

1. If issues are detected with the new version, update the Istio `VirtualService` configuration to route traffic back to the old version.
2. Apply the updated configuration using `kubectl apply`.
3. Investigate and fix the issues in the new version before attempting another deployment.

Conclusion

This walk-trough hopefully explained bit better how Blue/Green deployments using Kubernetes and Istio are achieved. Systems that are set this way minimize risks present while deploying new application versions and can ensure zero-downtime during the deployment process. Adopting this methodology in your DevOps projects will improve the reliability and stability of your systems.