How To Do Canary Deployments With Istio and Kubernetes

Introduction

When introducing new versions of a service, it is often desirable to shift a controlled percentage of user traffic to a newer version of the service in the process of phasing out the older version. This technique is called a canary deployment.

Kubernetes cluster operators can orchestrate canary deployments natively using labels and Deployments. This technique has certain limitations, however: traffic distribution and replica counts are coupled, which in practice means replica ratios must be controlled manually in order to limit traffic to the canary release. In other words, to direct 10% of traffic to a canary deployment, you would need to have a pool of ten pods, with one pod receiving 10% of user traffic, and the other nine receiving the rest.

Deploying with an Istio service mesh can address this issue by enabling a clear separation between replica counts and traffic management. The Istio mesh allows fine-grained traffic control that decouples traffic distribution and management from replica scaling. Instead of manually controlling replica ratios, you can define traffic percentages and targets, and Istio will manage the rest.

In this tutorial, you will create a canary deployment using Istio and Kubernetes. You will deploy two versions of a demo Node.js application, and use Virtual Service and Destination Rule resources to configure traffic routing to both the newer and older versions. This will be a good starting point to build out future canary deployments with Istio.