bprashanth/gslb.md

## gslb.md

      
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              gslb.md
            
          
    Start 2 kubernetes clusters.
Pick 1 node and label it as role=loadbalancer:
$ kubectl get nodes
NAME                              STATUS    AGE
gke-failover-c93a5565-node-bilp   Ready     1h
gke-failover-c93a5565-node-siro   Ready     1h
gke-failover-c93a5565-node-woat   Ready     1h

$ kubectl label node gke-failover-c93a5565-node-woat role=loadbalancer
Deploy services and serviceloadbalancer to each cluster, i.e create this yaml:
# This is the backend service
apiVersion: v1
kind: Service
metadata:
  name: hostname
  labels:
    app: hostname
spec:
  ports:
  - port: 80
    protocol: TCP
    targetPort: 9376
  selector:
    app: hostname
---
# This is the backend
apiVersion: v1
kind: ReplicationController
metadata:
  name: hostname
spec:
  replicas: 1
  template:
    metadata:
      labels:
        app: hostname
    spec:
      containers:
      - name: hostname
        image: gcr.io/google_containers/serve_hostname:1.2
        ports:
        - containerPort: 9376
---
# This is the frontend that needs to stick requests to backends
apiVersion: v1
kind: Service
metadata:
  name: haproxy
  labels:
    app: service-loadbalancer
spec:
  type: NodePort
  ports:
  - port: 80
  selector:
    app: service-loadbalancer
---
apiVersion: v1
kind: ReplicationController
metadata:
  name: service-loadbalancer
  labels:
    app: service-loadbalancer
    version: v1
spec:
  replicas: 1
  selector:
    app: service-loadbalancer
    version: v1
  template:
    metadata:
      labels:
        app: service-loadbalancer
        version: v1
    spec:
      nodeSelector:
        role: loadbalancer
      containers:
      - image: gcr.io/google_containers/servicelb:0.4
        imagePullPolicy: Always
        livenessProbe:
          httpGet:
            path: /healthz
            port: 8081
            scheme: HTTP
          initialDelaySeconds: 30
          timeoutSeconds: 5
        name: haproxy
        ports:
        # All http services
        - containerPort: 80
          hostPort: 80
          protocol: TCP
        # haproxy stats
        - containerPort: 1936
          hostPort: 1936
          protocol: TCP
        args:
        - --default-return-code=200

You now have 2 haproxies. Get their public ips:
$ kubectl get node gke-failover-c93a5565-node-woat -o yaml | grep -i external -B 5
...
someIP1
$ kubectl get node kubernetes-minion-x1w8 -o yaml | grep -i external -B 5
...
someIP2
Spin up a third haproxy with this config:
global
  daemon
  stats socket /tmp/haproxy

defaults
  log global
  option http-keep-alive
  timeout http-keep-alive 60s
  timeout http-request 5s
  timeout client 50s
  timeout server 50s
  mode http

frontend web
  mode http
  bind *:80
  default_backend web

backend web
  balance roundrobin
  option httpchk GET /hostname
  http-check expect status 200
  server cluster1 someIP1:80 check inter 1s fall 1 rise 2
  server cluster2 someIP2:80 check inter 1s fall 1 rise 2

Start up:
$ while true; do curl mainHaproxy/hostname; echo; sleep 1; done
hostname-jjfsb
hostname-wwkpj
hostname-jjfsb
hostname-wwkpj
Kill one cluster (or just kubectl delete rc service-loadbalancer).
hostname-jjfsb
<html><body><h1>503 Service Unavailable</h1>
No server is available to handle this request.
</body></html>
hostname-jjfsb
hostname-jjfsb
hostname-jjfsb
hostname-jjfsb
hostname-jjfsb