This page explains how to expose your application to external traffic. To learn about how Services work, refer to Service.
After you deploy an application to your cluster using a Deployment or StatefulSet object, its Pods are automatically assigned Pod IP addresses, which can be used to communicate within the cluster. To enable communication beyond the cluster, you need to expose the application to external traffic.
Pods be grouped into Services. Services target Pods using label selectors, which are defined in Pod specifications. When users access the Service, they are automatically load-balanced to a Pod that serves your application.
Before you begin
To prepare for this task, perform the following steps:
- Ensure that you have enabled the Kubernetes Engine API. Enable Kubernetes Engine API
- Ensure that you have installed the Cloud SDK.
- Set your default project ID:
gcloud config set project [PROJECT_ID]
- Set your default compute zone:
gcloud config set compute/zone [COMPUTE_ZONE]
- Update all
gcloudcommands to the latest version:
gcloud components update
Configuring a workload to accept external traffic
The following sections explain how to configure a workload to accept external traffic before exposing the workload.
Expose a port for your Pods
For a workload's Pods to accept traffic, you need to expose a port for the Pods to use. When you deploy a workload, such as a Deployment, you must specify a port to expose.
For example, suppose that you have created the following Deployment,
apiVersion: extensions/v1beta1 kind: Deployment metadata: name: my-app labels: run: my-app spec: replicas: 3 selector: matchLabels: run: my-app template: metadata: labels: run: my-app spec: containers: - image: gcr.io/google-samples/hello-app:1.0 name: my-app ports: - containerPort: 8080
my-app is labelled
run: my-app, runs on three replicated Pods, and opens
TCP port 8080 on each Pod.
Inspecting the exposed Pods
After deploying a workload, you should inspect its Pods to ensure their IP addresses are provisioned.
When you run
kubectl get pods -o wide, you see the following output, which
includes each Pod's IP address:
NAME READY STATUS RESTARTS AGE IP NODE my-app-3800858182-jr4a2 1/1 Running 0 13s 10.244.3.4 ... my-app-3800858182-kna2y 1/1 Running 0 13s 10.244.2.5 ...
If you connect to any node in the cluster, you can interact with Pods using their IP addresses. Because the Pods' containers do not use the exposed port, you can run multiple Pods on the same node without an overlap.
Creating a Service
You can create a Service in the following ways:
- Exposing an existing Pod or Deployment using
- Writing a Service manifest, then using
kubectl applyto deploy the resource.
- Using Google Cloud Platform Console.
When you run
kubectl expose, Kubernetes Engine creates a new Service that
automatically targets the workload you specify.
For example, consider the example Deployment,
the preceding section. The following command exposes
my-app. The command
LoadBalancer type Service named
kubectl expose deployment my-app --type=LoadBalancer --name=my-service
When you run
kubectl get service my-app -o=yaml, the following Service
manifest is returned:
apiVersion: v1 kind: Service metadata: labels: run: my-app name: my-service spec: clusterIP: 12.34.567.890 externalTrafficPolicy: Cluster ports: - nodePort: 32752 port: 8080 protocol: TCP targetPort: 8080 selector: run: my-app sessionAffinity: None type: LoadBalancer status: loadBalancer: ingress: - ip: 12.34.567.890
Since you didn't refer to a port in
kubectl expose, the Service uses the
Deployment's open port, 8080.
The following is an example of a Service manifest,
Service targets a set of Pods that expose port 8080 and are labelled
kind: Service apiVersion: v1 metadata: name: my-service # Service name spec: type: LoadBalancer selector: run: my-app # Label selector. The Service targets Pods that use this label ports: port: 80 # Port used to access the Service from within the cluster. targetPort: 8080 # Port opened by targeted Pods
To create this Service, run the following command:
kubectl apply -f config.yaml
To expose a workload, perform the following steps:
Visit the Kubernetes Engine Workloads menu in GCP Console.
Select the desired workload.
- Click Actions, then click Expose.
- From New port mapping, fill the Port field with the desired port and the Target port field with 80 (the container port).
- From the Service type drop-down menu, select Load balancer.
- Click Expose.
Inspecting the Service
To inspect the Service, run the following command:
kubectl describe service my-nginx
To inspect the Service, perform the following steps:
Visit the Kubernetes Engine Services menu in GCP Console.
Select the desired Service.
Whitelisting access to load balancers
When you create a
LoadBalancer Service, you can specify the IP ranges that are
allowed to access the load balancer in the
loadBalancerSourceRanges field of
your Service's specification. Currently, you can only specify this field when
you write a Service manifest file or by editing an existing Service.
To learn more, refer to Configure Your Cloud Provider's Firewalls in the Kubernetes documentation.