Let's take a look at the insight of the service using describe in the kubectl command. We will create one Kubernetes service with the type LoadBalancer, which will dispatch the traffic into two endpoints, 192.168.79.9 and 192.168.79.10 with port 80:
$ kubectl describe service my-first-nginx
Name: my-first-nginx
Namespace: default
Labels: run=my-first-nginx
Annotations: <none>
Selector: run=my-first-nginx
Type: LoadBalancer
IP: 10.103.85.175
Port: <unset> 80/TCP
TargetPort: 80/TCP
NodePort: <unset> 31723/TCP
Endpoints: 192.168.79.10:80,192.168.79.9:80
Session Affinity: None
External Traffic Policy: Cluster
Events: <none>
The port here is an abstract service port, which will allow any other resources to access the service within the cluster. The nodePort will be indicating the external port to allow external access. The targetPort is the port the container allows traffic into; by default, it will be the same port.
In the following diagram, external access will access the service with nodePort. The service acts as a load balancer to dispatch the traffic to the pod using port 80. The pod will then pass through the traffic into the corresponding container using targetPort 80:
In any nodes or master, once the inter-connection network is set up, you should be able to access the nginx service using ClusterIP 192.168.61.150 with port 80:
// curl from service IP
$ curl 10.103.85.175:80
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
body {
width: 35em;
margin: 0 auto;
font-family: Tahoma, Verdana, Arial, sans-serif;
}
</style>
</head>
<body>
<h1>Welcome to nginx!</h1>
<p>If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.</p>
<p>For online documentation and support please refer to
<a href="http://nginx.org/">nginx.org</a>.<br/>
Commercial support is available at
<a href="http://nginx.com/">nginx.com</a>.</p>
<p><em>Thank you for using nginx.</em></p>
</body>
</html>
It will be the same result if we curl to the target port of the pod directly:
// curl from endpoint, the content is the same as previous nginx html
$ curl 192.168.79.10:80
<!DOCTYPE html>
<html>
...
If you'd like to try out external access, use your browser to access the external IP address. Please note that the external IP address depends on which environment you're running in.
In the Google compute engine, you could access it via a ClusterIP with a proper rewall rules setting:
$ curl http://<clusterIP>
In a custom environment, such as on-premise data center, you could go through the IP address of nodes to access :
$ curl http://<nodeIP>:<nodePort>
You should be able to see the following page using a web browser:
