Add feature to allow sticky sessions per location

[aledbf]

This PR enables sticky session per location inside a server
Also avoids reusing the same upstream block when sticky sessions is not configured

kubectl create -f https://raw.githubusercontent.com/kubernetes/ingress/master/examples/http-svc.yaml

echo "
apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  annotations:
    ingress.kubernetes.io/affinity: cookie
    ingress.kubernetes.io/session-cookie-hash: sha1
    ingress.kubernetes.io/session-cookie-name: route
  name: nginx-test
  namespace: default
spec:
  rules:
  - host: sticky-ingress.example.com
    http:
      paths:
      - backend:
          serviceName: http-svc
          servicePort: 80
        path: /

---

apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  name: nginx-test-ns
  namespace: default
spec:
  rules:
  - host: no-sticky-ingress.example.com
    http:
      paths:
      - backend:
          serviceName: http-svc
          servicePort: 80
        path: /

---

apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  name: nginx-test-ns-path
  namespace: default
spec:
  rules:
  - host: sticky-ingress.example.com
    http:
      paths:
      - backend:
          serviceName: http-svc
          servicePort: 80
        # Add a custom path that use the same service without sticky sessions
        path: /no-sticky-session
" | kubectl create -f -

Check sticky sessions is working:

$ kubectl exec -n kube-system <ingress pod> -- curl -v localhost  -H'Host: sticky-ingress.example.com'

It must appear something like

< Set-Cookie: route=dc89ae303c62a8bfce8bf32f06d27c31f0980ef7; Path=/; HttpOnly

Check a different host with no sticky sessions that uses the same service:

$ kubectl exec -n kube-system <ingress pod> -- curl -v localhost  -H'Host: no-sticky-ingress.example.com'

Now check a different path in the host with sticky sessions where the feature is not enabled:

$ kubectl exec -n kube-system nginx-ingress-controller-3401347994-vjvhv  -it -- curl -v localhost/no-sticky-session  -H'Host: stickyingress.example.com'

fixes #844
fixes #771

[k8s-reviewable]

This change is 

[aledbf]

@rikatz ping

[coveralls]

Coverage increased (+0.02%) to 46.673% when pulling a8d9c8eb24c0291a86bc64c6631068a89a0181e2 on aledbf:fix-sticky into c6b5335 on kubernetes:master.

[rikatz]

@aledbf What happens here if we have multiple ingresses pointing to the same 'host', some with sticky enabled, other with only whitelist enabled?

Is there any conflict here that may happen?

I'll test this probably between today and tomorrow and will provide you a feedback :)

[aledbf]

Is there any conflict here that may happen?

No.

[coveralls]

Coverage increased (+0.01%) to 44.564% when pulling 83d03a1 on aledbf:fix-sticky into 955897a on kubernetes:master.

[garyyang85]

@aledbf I just follow these steps on my env, but I can not see anything like this:
< Set-Cookie: route=dc89ae303c62a8bfce8bf32f06d27c31f0980ef7; Path=/; HttpOnly

after run : kubectl exec -n kube-system -- curl -v localhost -H'Host: sticky-ingress.example.com'

just some output like this:

---

• Rebuilt URL to: localhost/
  % Total % Received % Xferd Average Speed Time Time Time Current
  Dload Upload Total Spent Left Speed
  0 0 0 0 0 0 0 0 --:--:-- --:--:-- --:--:-- 0* Trying ::1...
• Connected to localhost (::1) port 80 (#0)

GET / HTTP/1.1
Host: sticky-ingress.example.com
User-Agent: curl/7.47.0
Accept: /

< HTTP/1.1 200 OK
< Server: nginx/1.13.3
< Date: Thu, 17 Aug 2017 14:41:57 GMT
< Content-Type: text/plain
< Transfer-Encoding: chunked
< Connection: keep-alive
<
{ [679 bytes data]
100 672 0 672 0 0 98k 0 --:--:-- --:--:-- --:--:-- 109k

• Connection #0 to host localhost left intact

Hostname: http-svc-tzdt8

Pod Information:
node name: k8stest-7
pod name: http-svc-tzdt8
pod namespace: default
pod IP: 10.254.94.7

Server values:
server_version=nginx: 1.13.3 - lua: 10008

Request Information:
client_address=10.254.74.0
method=GET
real path=/
query=
request_version=1.1
request_uri=http://sticky-ingress.example.com:8080/

Request Headers:
accept=/
connection=close
host=sticky-ingress.example.com
user-agent=curl/7.47.0
x-forwarded-for=::1
x-forwarded-host=sticky-ingress.example.com
x-forwarded-port=80
x-forwarded-proto=http
x-original-uri=/
x-real-ip=::1
x-scheme=http

Request Body:
-no body in request-

---

I am using kubernetes 1.5.7 and nginx 0.9-beta.11