cluster-ip.md

ClusterIP

ClusterIP accesses the services through proxy. ClusterIP can access services only inside the cluster.

We can test this by running a simple HTTP client inside your Kubernetes Cluster

Test ClusterIP from a Internal client

1. We can deploy a utility container, network-tools, pod to test requests to our services via it's ClusterIP

# Use this manifest to create our dnsutil Pod:
kubectl apply -f deployments/tools/network-tools.yaml

pod/network-tools created

# Verify its status
kubectl get pods network-tools

NAME                READY     STATUS    RESTARTS   AGE
network-tools   1/1       Running   0          <some-time>

2. Get the ClusterIP address for our Coffee and Tea services (coffee-svc and tea-svc )

kubectl get services -n cafe

NAME         TYPE        CLUSTER-IP       EXTERNAL-IP   PORT(S)   AGE
coffee-svc   ClusterIP   10.100.104.173   <none>        80/TCP    50m
tea-svc      ClusterIP   10.100.23.145    <none>        80/TCP    50m

We can also save the ClusterIP addresses into variables for next step

# coffee-svc 
coffee_cluster_ip=$(kubectl get services/coffee-svc -n cafe | grep -Eo '[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}')

# tea-svc 
tea_cluster_ip=$(kubectl get services/tea-svc -n cafe | grep -Eo '[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}')

3. Now exec a curl command in that that pod to retrieve response header information from the coffee and tea services

# coffee-svc
kubectl exec -i -t network-tools -- curl http://$coffee_cluster_ip -I

HTTP/1.1 200 OK
Server: nginx/1.17.6
Date: Fri, 20 Nov 2020 20:43:22 GMT
Content-Type: text/html
Connection: keep-alive
Expires: Fri, 20 Nov 2020 20:43:21 GMT
Cache-Control: no-cache

# tea-svc
kubectl exec -i -t network-tools -- curl http://$tea_cluster_ip -I

HTTP/1.1 200 OK
Server: nginx/1.17.6
Date: Fri, 20 Nov 2020 20:52:35 GMT
Content-Type: text/html
Connection: keep-alive
Expires: Fri, 20 Nov 2020 20:52:34 GMT
Cache-Control: no-cache