Canary Controller

Canary Controller is a Custom Resource and Controller for managing Canary server.

Concept

The Canary Release is an approach to release a new application more safely. In short, the Canary Release consists of the following steps:

1. Deploy a new application. (called "Canary server")
2. Send some of the traffics to the Canary server. Typically we'd join a Canary server for the Load Balancer and Load Balancer routes traffic using the DNS round robin. In Kubernetes, Service assumes this role.
3. Evaluate a Canary server by comparing with other server deployed old application (called Baseline server) using some metrics, for example, RPS, resource usage, and error rate.
4. Roll out the new application to all servers OR rollback to the old version.

Canary Controller supports the second phase, managing a Canary server and routing. Canary Controller creates a Deployment of a Canary server based on the existing ones. Additionally, Deployment Canary Controller put some metadata to a generated Deployment for identifying whether an application is a Canary.

• Attach canary: true to Deployment's labels
• Give a name the host of Pod to canary
• Add CANARY_ENABLED: 1 to environment variables of all containers

Installation

This installation depends on kubectl and kustomize. If your environment is OSX then you can install these using the following commands:

$ brew install kubernetes-cli
$ brew install kustomize

You can deploy to your cluster using make command.

$ make deploy

Canary Controller is installed in canary-controller-system namespace.

Usage

Apply a very simple manifest if you want to deploy a Canary server:

apiVersion: canary.k8s.wantedly.com/v1beta1
kind: Canary
metadata:
  name: foo-canary
  namespace: default
spec:
  targetDeploymentName: foo
  targetContainers:
  - name: nginx
    image: nginx:latest

Canary Controller looks up existing Deployment named "foo" in the "default" namespace and creates a new Deployment based on "foo" and overrides the image of container named "nginx" to "nginx:latest":

$ kubectl get deploy -n default
NAME      DESIRED   CURRENT   UP-TO-DATE   AVAILABLE   AGE
foo       1         1         1            1           1m

$ kubectl get deploy foo -o json | jq '.spec.template.spec.containers[] | if .name == "nginx" then .image else empty end'
"nginx:1.15.4"

$ kubectl apply -f config/sample/canary_v1beta1_canary.yaml
canary.canary.k8s.wantedly.com "canary-sample" created

$ kubectl get deploy -n default
NAME         DESIRED   CURRENT   UP-TO-DATE   AVAILABLE   AGE
foo          1         1         1            1           1m
foo-canary   1         1         1            1           9s

$ kubectl get deploy foo-canary -o json | jq '.spec.template.spec.containers[] | if .name == "nginx" then .image else empty end'
"nginx:latest"

After testing the new Deployment, you can clean it up by running the following command:

$ kubectl delete -f config/sample/canary_v1beta1_canary.yaml
canary.canary.k8s.wantedly.com "canary-sample" deleted

$ kubectl get deploy
NAME      DESIRED   CURRENT   UP-TO-DATE   AVAILABLE   AGE
foo       1         1         1            1           1m