Deploy a Sample Application with Sticky Sessions (Experimental)¶

With persistent sessions, the Ingress controller can use a predetermined header or dynamically generate a HTTP header cookie for a client session to use, so that a clients requests are sent to the same back end.

This is specified within the Istio Object DestinationRule via a TrafficPolicy for a given host. In the following example configuration, consistentHash is chosen as the load balancing method and a cookie named “session” is used to determine the consistent hash. If incoming requests do not have the “session” cookie set, the Ingress proxy sets it for use in future requests.

1. Source a MKE Client Bundle attached to a cluster with Cluster Ingress installed.

2. Download the sample Kubernetes manifest file.

   $ wget https://raw.githubusercontent.com/docker/docker.github.io/master/ee/ucp/kubernetes/cluster-ingress/yaml/ingress-sticky.yaml
   

3. Deploy the Kubernetes manifest file with the new DestinationRule. This file includes the consistentHash loadBalancer policy.

   $ kubectl apply -f ingress-sticky.yaml
   

4. Curl the service to view how requests are load balanced without using cookies. In this example, requests are bounced between different v1 services.

# Public IP Address of a Worker or Manager VM in the Cluster
$ IPADDR=51.141.127.241

# Node Port
$ PORT=$(kubectl get service demo-service --output jsonpath='{.spec.ports[?(@.name=="http")].nodePort}')

$ for i in {1..5}; do curl -H "Host: demo.example.com" http://$IPADDR:$PORT/ping; done
{"instance":"demo-v1-7797b7c7c8-gfwzj","version":"v1","metadata":"production","request_id":"b40a0294-2629-413b-b876-76b59d72189b"}
{"instance":"demo-v1-7797b7c7c8-kw6gp","version":"v1","metadata":"production","request_id":"721fe4ba-a785-484a-bba0-627ee6e47188"}
{"instance":"demo-v1-7797b7c7c8-gfwzj","version":"v1","metadata":"production","request_id":"77ed801b-81aa-4c02-8cc9-7e3bd3244807"}
{"instance":"demo-v1-7797b7c7c8-gfwzj","version":"v1","metadata":"production","request_id":"36d8aaed-fcdf-4489-a85e-76ea96949d6c"}
{"instance":"demo-v1-7797b7c7c8-kw6gp","version":"v1","metadata":"production","request_id":"4693b6ad-286b-4470-9eea-c8656f6801ae"}

Now curl again and inspect the headers returned from the proxy.

$ curl -i -H "Host: demo.example.com" http://$IPADDR:$PORT/ping
HTTP/1.1 200 OK
set-cookie: session=1555389679134464956; Path=/; Expires=Wed, 17 Apr 2019 04:41:19 GMT; Max-Age=86400
date: Tue, 16 Apr 2019 04:41:18 GMT
content-length: 131
content-type: text/plain; charset=utf-8
x-envoy-upstream-service-time: 0
set-cookie: session="d7227d32eeb0524b"; Max-Age=60; HttpOnly
server: istio-envoy

{"instance":"demo-v1-7797b7c7c8-kw6gp","version":"v1","metadata":"production","request_id":"011d5fdf-2285-4ce7-8644-c2df6481c584"}

The Ingress proxy sets a 60 second TTL cookie named session on this HTTP request. A browser or other client application can use that value in future requests.

Now curl the service again using the flags that save cookies persistently across sessions. The header information shows the session is being set, persisted across requests, and that for a given session header, the responses are coming from the same back end.

$ for i in {1..5}; do curl -c cookie.txt -b cookie.txt -H "Host: demo.example.com" http://$IPADDR:$PORT/ping; done
{"instance":"demo-v1-7797b7c7c8-kw6gp","version":"v1","metadata":"production","request_id":"72b35296-d6bd-462a-9e62-0bd0249923d7"}
{"instance":"demo-v1-7797b7c7c8-kw6gp","version":"v1","metadata":"production","request_id":"c8872f6c-f77c-4411-aed2-d7aa6d1d92e9"}
{"instance":"demo-v1-7797b7c7c8-kw6gp","version":"v1","metadata":"production","request_id":"0e7b8725-c550-4923-acea-db94df1eb0e4"}
{"instance":"demo-v1-7797b7c7c8-kw6gp","version":"v1","metadata":"production","request_id":"9996fe77-8260-4225-89df-0eaf7581e961"}
{"instance":"demo-v1-7797b7c7c8-kw6gp","version":"v1","metadata":"production","request_id":"d35c380e-31d6-44ce-a5d0-f9f6179715ab"}

When the HTTP uses the cookie that is set by the Ingress proxy, all requests are sent to the same back end, demo-v1-7797b7c7c8-kw6gp.