Implement a Canary Release with Kong for Kubernetes and Consul

From the Kong API Gateway perspective, using Consul as its Service Discovery infrastructure is one of the most well-known and common integration use cases. With this powerful combination more flexible and advanced routing policies can be implemented to address Canary Releases, A/B testings, Blue-Green deployments, etc. totally abstracted from the Gateway standpoint without having to deal with lookup procedures.

This article focuses on integrating Kong for Kubernetes (K4K8S), the Kong Ingress Controller based on the Kong API Gateway, and Consul Service Discovery running on a Kubernetes EKS Cluster. Kong for Kubernetes can implement all sorts of policies to protect the Ingresses defined to expose Kubernetes services to external Consumers including Rate Limiting, API Keys, OAuth/OIDC grants, etc.

The following diagram describes the Kong for Kubernetes Ingress Controller and Consul Service Discovery implementing a Canary Release:

Consul and Kong for Kubernetes Installation Process

This section assumes you have a Kubernetes Cluster with both Consul and Kong for Kubernetes installed. This HashiCorp link can help you spin up a Consul Kubernetes deployment. Similarly, Kong provides the following link to install Kong for Kubernetes.

Consul Configuration Process

After getting your Kubernetes Cluster installed with Consul and Kong for Kubernetes deployed, we’re ready to start the 5-step configuration process:

1. Configure Kubernetes DNS Service
2. Deploy both Current and Canary application releases
3. Register a Consul Service based on both application releases
4. Create an External Kubernetes Service based on the Consul Service
5. Register a Kong for Kubernetes Ingress for the External Service

Configure Kubernetes DNS

First of all, let’s configure the Kubernetes in order to consume Consul’s primary query instance based on DNS. The configuration depends on the DNS provided by the Kubernetes engine you are using. Please, refer to this link to check how to configure KubeDNS or CoreDNS.

Once configured, DNS requests in the form <consul-service-name>.service.consul will resolve for Consul Services. As an example, here are the configuration steps for CoreDNS:

Get the Consul DNS’ Cluster IP:

Edit the CoreDNS ConfigMap to include a forward definition that points to the Consul DNS’s Kubernetes Services.

Deploy both Current and Canary application releases

For the purpose of this article we’re going to create our Kubernetes Deployments using basic Docker Images for both Current and Canary releases available in http://hub.docker.com. Both Images return the current datetime, differing from each other by the text used. As expected, after the deployment, you should see two Kubernetes Services: benigno-v1 and benigno-v2.

The Current application release can be deployed using the following declaration:

The Canary Release is deployed using the command below:

Register a Consul Service based on both application releases

Now, we have to register a Consul Service based on both Kubernetes Services we have deployed. The benigno1 Consul Service will have both Kubernetes Services’ Cluster IPs configured with different weights. So, any DNS request to it will return one of the IPs applying the weights defined.

In order to get the Kubernetes Services’ Cluster IPs run:

Then create two files as described below using the Cluster IPs. Notice the weights used saying that the Consul DNS will return the Canary Release IP address for only 20% of the requests:

ben0.json:

ben1.json:

Expose Consul using port-forward so we can send requests to it and get the Consul Service registered. On one local terminal run:

Open another local terminal to send the requests using the files created before. We’re using HTTPie to send the requests. Feel free to use any other tool.

Create an External Kubernetes Service based on the Consul Service

After registering the Consul Service, any DNS request to benigno1.service.consul will return one of the IPs applying the weight policy described. Now, we create an External Service to define a specific Kubernetes reference to the Consul Service.

Register a Kong for Kubernetes Ingress for the External Service

Finally we’re going to expose the Canary Release through an Ingress managed by Kong for Kubernetes. Using the External Service created before we abstract both Application releases under the Consul Service benigno1.service.consul name.

You can test the Ingress sending a request like this:

Start a loop to see the Canary Release in action:

Kong for Kubernetes provides CRDs not just to define Ingresses but also apply typical policies defined at the Ingress Controller layer. Feel free to experiment further policy implementations like caching, log processing, OIDC-based authentication, GraphQL integration and more with the extensive list of plugins provided by Kong.