Using Kong with Kubernetes

by Álex 2015-12-17 devops kong microservices kubernetes

This was originally posted on k8s.uk.

If you don’t know about Kong yet, you should take a look. It’s an Open Source API Gateway, they define themselves as: “The open-source management layer for APIs, delivering high performance and reliability.” and they are quite right.

I was playing with Kong lately at work (jobandtalent.com, we are hiring!) and I think that it could be pretty awesome as a entry layer to your microservices platform running in Kubernetes.

For the sake of simplicity I will not run Kong in Kubernetes, but it shouldn’t be so difficult since they already provide Docker images. Also, running Kong on the same cluster you will be able to use internal networking between pods: win-win.

So, what will I show?

Go & packing

I’ve created a small Go app that will show the value of an environment variable when you GET /:

package main

import (
  "fmt"
  "log"
  "net/http"
  "os"
)

func main() {
  http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
    fmt.Fprintf(w, os.Getenv("TEST_RESULT"))
  })

  log.Fatal(http.ListenAndServe(":8080", nil))
}

Now we will build the application to later pack it in our image. Remember that if you are in Mac you will need to cross-compile the app to work on Linux:

$ GOOS=linux go build

We can pack it into our images now. For doing so we need a Dockerfile. It’s a simple binary, so the Dockerfile is not complex at all:

FROM scratch
ADD app /
ENTRYPOINT ["/app"]

Cool! What can we do now with our shiny image? Yes, you are right! Push it to the hub:

$ docker build -t agonzalezro/kong-test .
$ docker push agonzalezro/kong-test

k8s

We have our image on the registry and all we need now is running it on Kubernetes. I am using Google Container Engine for deploying this, but you can use whatever you prefer.

Let’s create our RCs & services:

# rc1.yml
apiVersion: v1
kind: ReplicationController
metadata:
  name: api1
spec:
  selector:
    name: api
    version: first
  template:
    metadata:
      labels:
        name: api
        version: first
    spec:
      containers:
        - name: app
          image: agonzalezro/kong-test
          env:
            - name: TEST_RESULT
              value: "This is the first app"

# rc2.yml
apiVersion: v1
kind: ReplicationController
metadata:
  name: api2
spec:
  selector:
    name: api
    version: second
  template:
    metadata:
      labels:
        name: api
        version: second
    spec:
      containers:
        - name: app
          image: agonzalezro/kong-test
          env:
            - name: TEST_RESULT
              value: "Second!"

# svc1.yml
apiVersion: v1
kind: Service
metadata:
  name: app1-svc
spec:
  type: LoadBalancer
  ports:
    - port: 80
      targetPort: 8080
  selector:
    name: api
    version: first

# svc2.yml
apiVersion: v1
kind: Service
metadata:
  name: app2-svc
spec:
  type: LoadBalancer
  ports:
    - port: 80
      targetPort: 8080
  selector:
    name: api
    version: second

And now run it:

$ kubectl create -f rc1.yml -f rc2.yml -f svc1.yml -f svc2.yml

Wait for the service and the pods to be ready and check their IPS:

$ kubectl get services
NAME         CLUSTER_IP      EXTERNAL_IP      PORT(S)   SELECTOR                  AGE
app1-svc     10.159.242.86   130.211.89.175   80/TCP    name=api,version=first    17m
app2-svc     10.159.246.93   104.155.53.175   80/TCP    name=api,version=second   17m
kubernetes   10.159.240.1    <none>           443/TCP   <none>                    1h

Kong

Follow the instruction here: https://getkong.org/install/docker/ to install Kong locally.

Yeah! We have it up & running so let’s point it to our shinny cluster. We need to use Kong API for that (port :8001):

$ http http://dockerhost:8001/apis/ name=first upstream_url=http://130.211.89.175 request_path=/first strip_request_path=true
$ http http://dockerhost:8001/apis/ name=second upstream_url=http://104.155.53.175 request_path=/second strip_request_path=true

What we did here? We set up two new endpoints /first & /second that are pointing to the both Kubernetes services previously created. We could have done it with DNS as well using request_host instead.

Lets call Kong on the port :8000 to use them:

$ http http://dockerhost:8000/first
HTTP/1.1 200 OK
Connection: keep-alive
Content-Length: 21
Content-Type: text/plain; charset=utf-8
Date: Thu, 17 Dec 2015 21:43:41 GMT
Via: kong/0.5.4

This is the first app

$ http http://dockerhost:8000/second
HTTP/1.1 200 OK
Connection: keep-alive
Content-Length: 7
Content-Type: text/plain; charset=utf-8
Date: Thu, 17 Dec 2015 21:43:44 GMT
Via: kong/0.5.4

Second!

\o/ We did it!

Next steps

You have Kong pointed to your cluster, now it’s up to your imagination what to do next. I would say try to configure some rate limiting or auth, it’s deadly simply. Check them here: https://getkong.org/plugins/

If you have any question or you want to discuss this further let me know at @agonzalezro.


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