I've been banging my head against this wall on and off for a while. There is a ton of information on Kubernetes on the web, but it's all assuming so much knowledge that n00bs like me don't really have much to go on.

So, can anyone share a simple example of the following (as a yaml file)? All I want is

• two pods
• let's say one pod has a backend (I don't know - node.js), and one has a frontend (say React).
• A way to network between them.

And then an example of calling an api call from the back to the front.

I start looking into this sort of thing, and all of a sudden I hit this page - https://kubernetes.io/docs/concepts/cluster-administration/networking/#how-to-achieve-this. This is super unhelpful. I don't want or need advanced network policies, nor do I have the time to go through several different service layers that are mapped on top of kubernetes. I just want to figure out a trivial example of a network request.

Hopefully if this example exists on stackoverflow it will serve other people as well.

Any help would be appreciated. Thanks.

EDIT; it looks like the easiest example may be using the Ingress controller.

EDIT EDIT;

I'm working to try and get a minimal example deployed - I'll walk through some steps here and point out my issues.

So below is my yaml file:

apiVersion: apps/v1beta1
kind: Deployment
metadata:
  name: frontend
  labels:
    app: frontend
spec:
  replicas: 3
  selector:
    matchLabels:
      app: frontend
  template:
    metadata:
      labels:
        app: frontend
    spec:
      containers:
      - name: nginx
        image: patientplatypus/frontend_example
        ports:
        - containerPort: 3000
---
apiVersion: v1
kind: Service
metadata:
  name: frontend
spec:
  type: LoadBalancer
  selector:
    app: frontend
  ports:
    - protocol: TCP
      port: 80
      targetPort: 3000
---
apiVersion: apps/v1beta1
kind: Deployment
metadata:
  name: backend
  labels:
    app: backend
spec:
  replicas: 3
  selector:
    matchLabels:
      app: backend
  template:
    metadata:
      labels:
        app: backend
    spec:
      containers:
      - name: nginx
        image: patientplatypus/backend_example
        ports:
        - containerPort: 5000
---
apiVersion: v1
kind: Service
metadata:
  name: backend
spec:
  type: LoadBalancer
  selector:
    app: backend
  ports:
    - protocol: TCP
      port: 80
      targetPort: 5000
---
apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  name: frontend
spec:      
  rules:
  - host: www.kubeplaytime.example
    http:
      paths:
      - path: /
        backend:
          serviceName: frontend
          servicePort: 80
      - path: /api
        backend:
          serviceName: backend
          servicePort: 80

What I believe this is doing is

• Deploying a frontend and backend app - I deployed patientplatypus/frontend_example and patientplatypus/backend_example to dockerhub and then pull the images down. One open question I have is, what if I don't want to pull the images from docker hub and rather would just like to load from my localhost, is that possible? In this case I would push my code to the production server, build the docker images on the server and then upload to kubernetes. The benefit is that I don't have to rely on dockerhub if I want my images to be private.

• It is creating two service endpoints that route outside traffic from a web browser to each of the deployments. These services are of type loadBalancer because they are balancing the traffic among the (in this case 3) replicasets that I have in the deployments.

• Finally, I have an ingress controller which is supposed to allow my services to route to each other through www.kubeplaytime.example and www.kubeplaytime.example/api. However this is not working.

What happens when I run this?

patientplatypus:~/Documents/kubePlay:09:17:50$kubectl create -f kube-deploy.yaml
deployment.apps "frontend" created
service "frontend" created
deployment.apps "backend" created
service "backend" created
ingress.extensions "frontend" created

• So first, it appears to create all the parts that I need fine with no errors.

  patientplatypus:~/Documents/kubePlay:09:22:30$kubectl get --watch services

  NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE

  backend LoadBalancer 10.0.18.174 <pending> 80:31649/TCP 1m

  frontend LoadBalancer 10.0.100.65 <pending> 80:32635/TCP 1m

  kubernetes ClusterIP 10.0.0.1 <none> 443/TCP 10d

  frontend LoadBalancer 10.0.100.65 138.91.126.178 80:32635/TCP 2m

  backend LoadBalancer 10.0.18.174 138.91.121.182 80:31649/TCP 2m

• Second, if I watch the services, I eventually get IP addresses that I can use to navigate in my browser to these sites. Each of the above IP addresses works in routing me to the frontend and backend respectively.

HOWEVER

I reach an issue when I try and use the ingress controller - it seemingly deployed, but I don't know how to get there.

patientplatypus:~/Documents/kubePlay:09:24:44$kubectl get ingresses
NAME       HOSTS                      ADDRESS   PORTS     AGE
frontend   www.kubeplaytime.example             80        16m

• So I have no address I can use, and www.kubeplaytime.example does not appear to work.

What it appears that I have to do to route to the ingress extension I just created is to use a service and deployment on it in order to get an IP address, but this starts to look incredibly complicated very quickly.

For example, take a look at this medium article: https://medium.com/@cashisclay/kubernetes-ingress-82aa960f658e.

It would appear that the necessary code to add for just the service routing to the Ingress (ie what he calls the Ingress Controller) appears to be this:

---
kind: Service
apiVersion: v1
metadata:
  name: ingress-nginx
spec:
  type: LoadBalancer
  selector:
    app: ingress-nginx
  ports:
  - name: http
    port: 80
    targetPort: http
  - name: https
    port: 443
    targetPort: https
---
kind: Deployment
apiVersion: extensions/v1beta1
metadata:
  name: ingress-nginx
spec:
  replicas: 1
  template:
    metadata:
      labels:
        app: ingress-nginx
    spec:
      terminationGracePeriodSeconds: 60
      containers:
      - image: gcr.io/google_containers/nginx-ingress-controller:0.8.3
        name: ingress-nginx
        imagePullPolicy: Always
        ports:
          - name: http
            containerPort: 80
            protocol: TCP
          - name: https
            containerPort: 443
            protocol: TCP
        livenessProbe:
          httpGet:
            path: /healthz
            port: 10254
            scheme: HTTP
          initialDelaySeconds: 30
          timeoutSeconds: 5
        env:
          - name: POD_NAME
            valueFrom:
              fieldRef:
                fieldPath: metadata.name
          - name: POD_NAMESPACE
            valueFrom:
              fieldRef:
                fieldPath: metadata.namespace
        args:
        - /nginx-ingress-controller
        - --default-backend-service=$(POD_NAMESPACE)/nginx-default-backend
---
kind: Service
apiVersion: v1
metadata:
  name: nginx-default-backend
spec:
  ports:
  - port: 80
    targetPort: http
  selector:
    app: nginx-default-backend
---
kind: Deployment
apiVersion: extensions/v1beta1
metadata:
  name: nginx-default-backend
spec:
  replicas: 1
  template:
    metadata:
      labels:
        app: nginx-default-backend
    spec:
      terminationGracePeriodSeconds: 60
      containers:
      - name: default-http-backend
        image: gcr.io/google_containers/defaultbackend:1.0
        livenessProbe:
          httpGet:
            path: /healthz
            port: 8080
            scheme: HTTP
          initialDelaySeconds: 30
          timeoutSeconds: 5
        resources:
          limits:
            cpu: 10m
            memory: 20Mi
          requests:
            cpu: 10m
            memory: 20Mi
        ports:
        - name: http
          containerPort: 8080
          protocol: TCP

This would seemingly need to be appended to my other yaml code above in order to get a service entry point for my ingress routing, and it does appear to give an ip:

patientplatypus:~/Documents/kubePlay:09:54:12$kubectl get --watch services
NAME                    TYPE           CLUSTER-IP    EXTERNAL-IP   PORT(S)                      AGE
backend                 LoadBalancer   10.0.31.209   <pending>     80:32428/TCP                 4m
frontend                LoadBalancer   10.0.222.47   <pending>     80:32482/TCP                 4m
ingress-nginx           LoadBalancer   10.0.28.157   <pending>     80:30573/TCP,443:30802/TCP   4m
kubernetes              ClusterIP      10.0.0.1      <none>        443/TCP                      10d
nginx-default-backend   ClusterIP      10.0.71.121   <none>        80/TCP                       4m
frontend   LoadBalancer   10.0.222.47   40.121.7.66   80:32482/TCP   5m
ingress-nginx   LoadBalancer   10.0.28.157   40.121.6.179   80:30573/TCP,443:30802/TCP   6m
backend   LoadBalancer   10.0.31.209   40.117.248.73   80:32428/TCP   7m

So ingress-nginx appears to be the site I want to get to. Navigating to 40.121.6.179 returns a default 404 message (default backend - 404) - it does not go to frontend as / aught to route. /api returns the same. Navigating to my host namespace www.kubeplaytime.example returns a 404 from the browser - no error handling.

QUESTIONS

• Is the Ingress Controller strictly necessary, and if so is there a less complicated version of this?

• I feel I am close, what am I doing wrong?

FULL YAML

Available here: https://gist.github.com/patientplatypus/fa07648339ee6538616cb69282a84938

Thanks for the help!

EDIT EDIT EDIT

I've attempted to use HELM. On the surface it appears to be a simple interface, and so I tried spinning it up:

patientplatypus:~/Documents/kubePlay:12:13:00$helm install stable/nginx-ingress
NAME:   erstwhile-beetle
LAST DEPLOYED: Sun May  6 12:13:30 2018
NAMESPACE: default
STATUS: DEPLOYED

RESOURCES:
==> v1/ConfigMap
NAME                                       DATA  AGE
erstwhile-beetle-nginx-ingress-controller  1     1s

==> v1/Service
NAME                                            TYPE          CLUSTER-IP   EXTERNAL-IP  PORT(S)                     AGE
erstwhile-beetle-nginx-ingress-controller       LoadBalancer  10.0.216.38  <pending>    80:31494/TCP,443:32118/TCP  1s
erstwhile-beetle-nginx-ingress-default-backend  ClusterIP     10.0.55.224  <none>       80/TCP                      1s

==> v1beta1/Deployment
NAME                                            DESIRED  CURRENT  UP-TO-DATE  AVAILABLE  AGE
erstwhile-beetle-nginx-ingress-controller       1        1        1           0          1s
erstwhile-beetle-nginx-ingress-default-backend  1        1        1           0          1s

==> v1beta1/PodDisruptionBudget
NAME                                            MIN AVAILABLE  MAX UNAVAILABLE  ALLOWED DISRUPTIONS  AGE
erstwhile-beetle-nginx-ingress-controller       1              N/A              0                    1s
erstwhile-beetle-nginx-ingress-default-backend  1              N/A              0                    1s

==> v1/Pod(related)
NAME                                                             READY  STATUS             RESTARTS  AGE
erstwhile-beetle-nginx-ingress-controller-7df9b78b64-24hwz       0/1    ContainerCreating  0         1s
erstwhile-beetle-nginx-ingress-default-backend-849b8df477-gzv8w  0/1    ContainerCreating  0         1s


NOTES:
The nginx-ingress controller has been installed.
It may take a few minutes for the LoadBalancer IP to be available.
You can watch the status by running 'kubectl --namespace default get services -o wide -w erstwhile-beetle-nginx-ingress-controller'

An example Ingress that makes use of the controller:

  apiVersion: extensions/v1beta1
  kind: Ingress
  metadata:
    annotations:
      kubernetes.io/ingress.class: nginx
    name: example
    namespace: foo
  spec:
    rules:
      - host: www.example.com
        http:
          paths:
            - backend:
                serviceName: exampleService
                servicePort: 80
              path: /
    # This section is only required if TLS is to be enabled for the Ingress
    tls:
        - hosts:
            - www.example.com
          secretName: example-tls

If TLS is enabled for the Ingress, a Secret containing the certificate and key must also be provided:

  apiVersion: v1
  kind: Secret
  metadata:
    name: example-tls
    namespace: foo
  data:
    tls.crt: <base64 encoded cert>
    tls.key: <base64 encoded key>
  type: kubernetes.io/tls

Seemingly this is really nice - it spins everything up and gives an example of how to add an ingress. Since I spun up helm in a blank kubectl I used the following yaml file to add in what I thought would be required.

The file:

apiVersion: apps/v1beta1
kind: Deployment
metadata:
  name: frontend
  labels:
    app: frontend
spec:
  replicas: 3
  selector:
    matchLabels:
      app: frontend
  template:
    metadata:
      labels:
        app: frontend
    spec:
      containers:
      - name: nginx
        image: patientplatypus/frontend_example
        ports:
        - containerPort: 3000
---
apiVersion: v1
kind: Service
metadata:
  name: frontend
spec:
  type: LoadBalancer
  selector:
    app: frontend
  ports:
    - protocol: TCP
      port: 80
      targetPort: 3000
---
apiVersion: apps/v1beta1
kind: Deployment
metadata:
  name: backend
  labels:
    app: backend
spec:
  replicas: 3
  selector:
    matchLabels:
      app: backend
  template:
    metadata:
      labels:
        app: backend
    spec:
      containers:
      - name: nginx
        image: patientplatypus/backend_example
        ports:
        - containerPort: 5000
---
apiVersion: v1
kind: Service
metadata:
  name: backend
spec:
  type: LoadBalancer
  selector:
    app: backend
  ports:
    - protocol: TCP
      port: 80
      targetPort: 5000
---
apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  annotations:
    kubernetes.io/ingress.class: nginx
spec:
  rules:
    - host: www.example.com
      http:
        paths:
          - path: /api
            backend:
              serviceName: backend
              servicePort: 80
          - path: /
            frontend:
              serviceName: frontend
              servicePort: 80

Deploying this to the cluster however runs into this error:

patientplatypus:~/Documents/kubePlay:11:44:20$kubectl create -f kube-deploy.yaml
deployment.apps "frontend" created
service "frontend" created
deployment.apps "backend" created
service "backend" created
error: error validating "kube-deploy.yaml": error validating data: [ValidationError(Ingress.spec.rules[0].http.paths[1]): unknown field "frontend" in io.k8s.api.extensions.v1beta1.HTTPIngressPath, ValidationError(Ingress.spec.rules[0].http.paths[1]): missing required field "backend" in io.k8s.api.extensions.v1beta1.HTTPIngressPath]; if you choose to ignore these errors, turn validation off with --validate=false

So, the question then becomes, well crap how do I debug this? If you spit out the code that helm produces, it's basically non-readable by a person - there's no way to go in there and figure out what's going on.

Check it out: https://gist.github.com/patientplatypus/0e281bf61307f02e16e0091397a1d863 - over a 1000 lines!

If anyone has a better way to debug a helm deploy add it to the list of open questions.

EDIT EDIT EDIT EDIT

To simplify in the extreme I attempt to make a call from one pod to another only using namespace.

So here is my React code where I make the http request:

axios.get('http://backend/test')
.then(response=>{
  console.log('return from backend and response: ', response);
})
.catch(error=>{
  console.log('return from backend and error: ', error);
})

I've also attempted to use http://backend.exampledeploy.svc.cluster.local/test without luck.

Here is my node code handling the get:

router.get('/test', function(req, res, next) {
  res.json({"test":"test"})
});

Here is my yaml file that I uploading to the kubectl cluster:

apiVersion: apps/v1beta1
kind: Deployment
metadata:
  name: frontend
  namespace: exampledeploy
  labels:
    app: frontend
spec:
  replicas: 3
  selector:
    matchLabels:
      app: frontend
  template:
    metadata:
      labels:
        app: frontend
    spec:
      containers:
      - name: nginx
        image: patientplatypus/frontend_example
        ports:
        - containerPort: 3000
---
apiVersion: v1
kind: Service
metadata:
  name: frontend
  namespace: exampledeploy
spec:
  type: LoadBalancer
  selector:
    app: frontend
  ports:
    - protocol: TCP
      port: 80
      targetPort: 3000
---
apiVersion: apps/v1beta1
kind: Deployment
metadata:
  name: backend
  namespace: exampledeploy
  labels:
    app: backend
spec:
  replicas: 3
  selector:
    matchLabels:
      app: backend
  template:
    metadata:
      labels:
        app: backend
    spec:
      containers:
      - name: nginx
        image: patientplatypus/backend_example
        ports:
        - containerPort: 5000
---
apiVersion: v1
kind: Service
metadata:
  name: backend
  namespace: exampledeploy
spec:
  type: LoadBalancer
  selector:
    app: backend
  ports:
    - protocol: TCP
      port: 80
      targetPort: 5000

The uploading to the cluster appears to work as I can see in my terminal:

patientplatypus:~/Documents/kubePlay:14:33:20$kubectl get all --namespace=exampledeploy 
NAME                            READY     STATUS    RESTARTS   AGE
pod/backend-584c5c59bc-5wkb4    1/1       Running   0          15m
pod/backend-584c5c59bc-jsr4m    1/1       Running   0          15m
pod/backend-584c5c59bc-txgw5    1/1       Running   0          15m
pod/frontend-647c99cdcf-2mmvn   1/1       Running   0          15m
pod/frontend-647c99cdcf-79sq5   1/1       Running   0          15m
pod/frontend-647c99cdcf-r5bvg   1/1       Running   0          15m

NAME               TYPE           CLUSTER-IP     EXTERNAL-IP      PORT(S)        AGE
service/backend    LoadBalancer   10.0.112.160   168.62.175.155   80:31498/TCP   15m
service/frontend   LoadBalancer   10.0.246.212   168.62.37.100    80:31139/TCP   15m

NAME                             DESIRED   CURRENT   UP-TO-DATE   AVAILABLE   AGE
deployment.extensions/backend    3         3         3            3           15m
deployment.extensions/frontend   3         3         3            3           15m

NAME                                        DESIRED   CURRENT   READY     AGE
replicaset.extensions/backend-584c5c59bc    3         3         3         15m
replicaset.extensions/frontend-647c99cdcf   3         3         3         15m

NAME                       DESIRED   CURRENT   UP-TO-DATE   AVAILABLE   AGE
deployment.apps/backend    3         3         3            3           15m
deployment.apps/frontend   3         3         3            3           15m

NAME                                  DESIRED   CURRENT   READY     AGE
replicaset.apps/backend-584c5c59bc    3         3         3         15m
replicaset.apps/frontend-647c99cdcf   3         3         3         15m

However, when I attempt to make the request I get the following error:

return from backend and error:  
Error: Network Error
Stack trace:
createError@http://168.62.37.100/static/js/bundle.js:1555:15
handleError@http://168.62.37.100/static/js/bundle.js:1091:14
App.js:14

Since the axios call is being made from the browser, I'm wondering if it is simply not possible to use this method to call the backend, even though the backend and the frontend are in different pods. I'm a little lost, as I thought this was the simplest possible way to network pods together.

EDIT X5

I've determined that it is possible to curl the backend from the command line by exec'ing into the pod like this:

patientplatypus:~/Documents/kubePlay:15:25:25$kubectl exec -ti frontend-647c99cdcf-5mfz4 --namespace=exampledeploy -- curl -v http://backend/test
* Hostname was NOT found in DNS cache
*   Trying 10.0.249.147...
* Connected to backend (10.0.249.147) port 80 (#0)
> GET /test HTTP/1.1
> User-Agent: curl/7.38.0
> Host: backend
> Accept: */*
> 
< HTTP/1.1 200 OK
< X-Powered-By: Express
< Content-Type: application/json; charset=utf-8
< Content-Length: 15
< ETag: W/"f-SzkCEKs7NV6rxiz4/VbpzPnLKEM"
< Date: Sun, 06 May 2018 20:25:49 GMT
< Connection: keep-alive
< 
* Connection #0 to host backend left intact
{"test":"test"}

What this means is, without a doubt, because the front end code is being executed in the browser it needs Ingress to gain entry into the pod, as http requests from the front end are what's breaking with simple pod networking. I was unsure of this, but it means Ingress is necessary.