Blue/green

This example demonstrates how to configure blue/green deployment on HAProxy Ingress controller, in order to route requests based on distict weight on deployment groups as well as selecting a group based on http header or cookie value.

Prerequisites

This document has the following prerequisite:

• A Kubernetes cluster with a running HAProxy Ingress controller v0.6 or above. See the five minutes deployment or the deployment example

Deploying applications

In order to the configuration have effect, at least two deployments, or daemon sets, or replication controllers should be used with at least two pairs of label name/value.

The following instructions create two deployment objects using run label as the service selector and group label as the blue/green deployment selector:

$ kubectl run blue \
  --image=jcmoraisjr/whoami \
  --port=8000 --labels=run=bluegreen,group=blue
deployment "blue" created

$ kubectl run green \
  --image=jcmoraisjr/whoami \
  --port=8000 --labels=run=bluegreen,group=green
deployment "green" created

Certify that the pods are running and have the correct labels. Note that both group and run labels were applied:

$ kubectl get pod -lrun=bluegreen --show-labels
NAME                     READY     STATUS    RESTARTS   AGE       LABELS
blue-79c9b67d5b-5hd2r    1/1       Running   0          35s       group=blue,pod-template-hash=3575623816,run=bluegreen
green-7546d648c4-p7pmz   1/1       Running   0          28s       group=green,pod-template-hash=3102820470,run=bluegreen

Configure

Create a service that bind both deployments together using the run label. The expose command need a deployment object, take anyone, we will override it’s selector:

$ kubectl expose deploy blue --name bluegreen --selector=run=bluegreen
service "bluegreen" exposed

$ kubectl get svc bluegreen -otemplate --template '{{.spec.selector}}'
map[run:bluegreen]

Check also the endpoints, it should list both blue and green pods:

$ kubectl get ep bluegreen
NAME         ENDPOINTS                           AGE
bluegreen    172.17.0.11:8000,172.17.0.19:8000   2m

$ kubectl get pod -lrun=bluegreen -owide
NAME                     READY     STATUS    RESTARTS   AGE       IP            NODE
blue-79c9b67d5b-5hd2r    1/1       Running   0          2m        172.17.0.11   192.168.100.99
green-7546d648c4-p7pmz   1/1       Running   0          2m        172.17.0.19   192.168.100.99

Configure the ingress resource. No need to change the host below, bluegreen.example.com is fine:

$ kubectl create -f - <<EOF
apiVersion: networking.k8s.io/v1beta1
kind: Ingress
metadata:
  annotations:
    ingress.kubernetes.io/balance-algorithm: roundrobin
    ingress.kubernetes.io/blue-green-deploy: group=blue=1,group=green=1
    ingress.kubernetes.io/blue-green-mode: pod
    ingress.kubernetes.io/ssl-redirect: "false"
  name: bluegreen
spec:
  rules:
  - host: bluegreen.example.com
    http:
      paths:
      - backend:
          serviceName: bluegreen
          servicePort: 8000
        path: /
EOF

$ kubectl get ing
NAME        HOSTS                   ADDRESS   PORTS     AGE
bluegreen   bluegreen.example.com             80        11s

Test blue/green balance

Lets test! The following snippets use an alias hareq declared below. Change IP to your HAProxy Ingress controller IP address:

$ IP=192.168.100.99
$ alias hareq='echo Running 100 requests...; for i in `seq 1 100`; do
    curl -fsS $IP -H "Host: bluegreen.example.com" | cut -d- -f1
  done | sort | uniq -c'

• BG Mode: pod
• BG Balance: blue=1, green=1

• Replicas: blue=1, green=1

  $ hareq
  Running 100 requests...
  50 blue
  50 green
  

---

Now changing green replicas to 3 and wait all the replicas to be running. BG Mode is pod, so the number of replicas will increase the load of the green deployment.

$ kubectl scale deploy green --replicas=3
$ kubectl get pod -w

• BG Mode: pod
• BG Balance: blue=1, green=1

• Replicas: blue=1, green=3

  $ hareq
  Running 100 requests...
  25 blue
  75 green
  

---

Changing to deploy mode. This mode targets the balance config to the whole deployment instead of single pods.

Note: BG mode was added on v0.7. On v0.6, the only supported mode is pod.

$ kubectl annotate --overwrite ingress bluegreen \
  ingress.kubernetes.io/blue-green-mode=deploy

• BG Mode: deploy
• BG Balance: blue=1, green=1

• Replicas: blue=1, green=3

  $ hareq
  Running 100 requests...
  50 blue
  50 green
  

---

Changing now the balance to ¹⁄₃ blue and ²⁄₃ green:

$ kubectl annotate --overwrite ingress bluegreen \
  ingress.kubernetes.io/blue-green-deploy=group=blue=1,group=green=2

• BG Mode: deploy
• BG Balance: blue=1, green=2

• Replicas: blue=1, green=3

  $ hareq
  Running 100 requests...
  33 blue
  67 green
  

---

The balance will be the same despite the number of replicas:

$ kubectl scale deploy green --replicas=6
$ kubectl get pod -w

• BG Mode: deploy
• BG Balance: blue=1, green=2

• Replicas: blue=1, green=6

  $ hareq
  Running 100 requests...
  33 blue
  67 green
  

Test blue/green selector

Blue/green selector requires HAProxy Ingress controller v0.9 or above.

Follow the deployment and configuration instructions to deploy the sample application.

After that, add the following annotation:

$ kubectl annotate --overwrite ingress bluegreen \
  ingress.kubernetes.io/blue-green-header=x-server:group

Create (or update) the hareq alias. Change IP to your HAProxy Ingress controller IP address:

$ IP=192.168.100.99
$ alias hareq='echo Running 100 requests...; for i in `seq 1 100`; do
    curl -fsS $IP -H "Host: bluegreen.example.com" -H "X-Server: $GROUP" | cut -d- -f1
  done | sort | uniq -c'

Choose blue group:

$ GROUP=blue

The envvar GROUP will populate the X-Server header with the value blue.

Run the requests:

$ hareq
Running 100 requests...
 100 blue

Choose green group:

$ GROUP=blue
$ hareq
Running 100 requests...
 100 green

Choose an invalid group, the configured blue/green balance will be used:

$ kubectl annotate --overwrite ingress bluegreen \
  ingress.kubernetes.io/blue-green-deploy=group=blue=1,group=green=3
$ GROUP=invalid
$ hareq
Running 100 requests...
  25 blue
  75 green