Exposing an External IP Address to Access an Application in a Cluster
This page shows how to create a Kubernetes Service object that exposes an external IP address.
- Objectives
- Before you begin
- Creating a service for an application running in five pods
- Cleaning up
- What’s next
Objectives
- Run five instances of a Hello World application.
- Create a Service object that exposes an external IP address.
- Use the Service object to access the running application.
Before you begin
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Install kubectl.
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Use a cloud provider like Google Kubernetes Engine or Amazon Web Services to create a Kubernetes cluster. This tutorial creates an external load balancer, which requires a cloud provider.
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Configure
kubectlto communicate with your Kubernetes API server. For instructions, see the documentation for your cloud provider.
Creating a service for an application running in five pods
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Run a Hello World application in your cluster:
kubectl run hello-world --replicas=5 --labels="run=load-balancer-example" --image=gcr.io/google-samples/node-hello:1.0 --port=8080The preceding command creates a Deployment object and an associated ReplicaSet object. The ReplicaSet has five Pods, each of which runs the Hello World application.
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Display information about the Deployment:
kubectl get deployments hello-world kubectl describe deployments hello-world -
Display information about your ReplicaSet objects:
kubectl get replicasets kubectl describe replicasets -
Create a Service object that exposes the deployment:
kubectl expose deployment hello-world --type=LoadBalancer --name=my-service -
Display information about the Service:
kubectl get services my-serviceThe output is similar to this:
NAME CLUSTER-IP EXTERNAL-IP PORT(S) AGE my-service 10.3.245.137 104.198.205.71 8080/TCP 54sNote: If the external IP address is shown as <pending>, wait for a minute and enter the same command again.
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Display detailed information about the Service:
kubectl describe services my-serviceThe output is similar to this:
Name: my-service Namespace: default Labels: run=load-balancer-example Annotations: <none> Selector: run=load-balancer-example Type: LoadBalancer IP: 10.3.245.137 LoadBalancer Ingress: 104.198.205.71 Port: <unset> 8080/TCP NodePort: <unset> 32377/TCP Endpoints: 10.0.0.6:8080,10.0.1.6:8080,10.0.1.7:8080 + 2 more... Session Affinity: None Events: <none>Make a note of the external IP address exposed by your service. In this example, the external IP address is 104.198.205.71. Also note the value of Port. In this example, the port is 8080.
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In the preceding output, you can see that the service has several endpoints: 10.0.0.6:8080,10.0.1.6:8080,10.0.1.7:8080 + 2 more. These are internal addresses of the pods that are running the Hello World application. To verify these are pod addresses, enter this command:
kubectl get pods --output=wideThe output is similar to this:
NAME ... IP NODE hello-world-2895499144-1jaz9 ... 10.0.1.6 gke-cluster-1-default-pool-e0b8d269-1afc hello-world-2895499144-2e5uh ... 10.0.1.8 gke-cluster-1-default-pool-e0b8d269-1afc hello-world-2895499144-9m4h1 ... 10.0.0.6 gke-cluster-1-default-pool-e0b8d269-5v7a hello-world-2895499144-o4z13 ... 10.0.1.7 gke-cluster-1-default-pool-e0b8d269-1afc hello-world-2895499144-segjf ... 10.0.2.5 gke-cluster-1-default-pool-e0b8d269-cpuc -
Use the external IP address to access the Hello World application:
curl http://<external-ip>:<port>where
<external-ip>is the external IP address of your Service, and<port>is the value ofPortin your Service description.The response to a successful request is a hello message:
Hello Kubernetes!
Cleaning up
To delete the Service, enter this command:
kubectl delete services my-service
To delete the Deployment, the ReplicaSet, and the Pods that are running the Hello World application, enter this command:
kubectl delete deployment hello-world
What’s next
Learn more about connecting applications with services.