Get the hostname of a Compute Engine instance

This sample retrieves the hostname of a given Compute Engine instance.

Code sample

Go

Before trying this sample, follow the Go setup instructions in the Compute Engine quickstart using client libraries. For more information, see the Compute Engine Go API reference documentation.

To authenticate to Compute Engine, set up Application Default Credentials. For more information, see Set up authentication for a local development environment.

import (
	"context"
	"fmt"
	"io"

	compute "cloud.google.com/go/compute/apiv1"
	computepb "cloud.google.com/go/compute/apiv1/computepb"
)

// getInstanceHostname prints the hostname of the Google Cloud VM instance.
func getInstanceHostname(w io.Writer, projectID, zone, instanceName string) error {
	// projectID := "your_project_id"
	// zone := "europe-central2-b"
	// instanceName := "your_instance_name"

	ctx := context.Background()
	instancesClient, err := compute.NewInstancesRESTClient(ctx)
	if err != nil {
		return fmt.Errorf("NewInstancesRESTClient: %w", err)
	}
	defer instancesClient.Close()

	req := &computepb.GetInstanceRequest{
		Project:  projectID,
		Zone:     zone,
		Instance: instanceName,
	}

	instance, err := instancesClient.Get(ctx, req)
	if err != nil {
		return fmt.Errorf("unable to get instance: %w", err)
	}

	// If a custom hostname is not set, the output for instance.GetHostname() will be ""
	fmt.Fprintf(w, "Instance %v has hostname: %v", instanceName, instance.GetHostname())

	return nil
}

Java

Before trying this sample, follow the Java setup instructions in the Compute Engine quickstart using client libraries. For more information, see the Compute Engine Java API reference documentation.

To authenticate to Compute Engine, set up Application Default Credentials. For more information, see Set up authentication for a local development environment.

import com.google.cloud.compute.v1.Instance;
import com.google.cloud.compute.v1.InstancesClient;
import java.io.IOException;

public class GetInstanceHostname {

  public static void main(String[] args) throws IOException {
    // TODO(developer): Replace these variables before running the sample.
    String project = "your-project-id";
    String zone = "zone-name"; // eg: "us-central1-a"
    String instanceName = "instance-name"; // Name of the VM instance to retrieve.

    getInstanceHostname(project, zone, instanceName);
  }

  // Retrieves the hostname of the Google Cloud VM instance.
  public static void getInstanceHostname(String projectId, String zone, String instanceName)
      throws IOException {
    try (InstancesClient instancesClient = InstancesClient.create()) {

      Instance instance = instancesClient.get(projectId, zone, instanceName);

      if (instance.hasHostname()) {
        // If a custom hostname is not set, the output for instance.getHostname() will be undefined.
        System.out.printf("Custom Hostname for the instance %s is: %s", instanceName,
            instance.getHostname());
      }
    }
  }

}

Node.js

Before trying this sample, follow the Node.js setup instructions in the Compute Engine quickstart using client libraries. For more information, see the Compute Engine Node.js API reference documentation.

To authenticate to Compute Engine, set up Application Default Credentials. For more information, see Set up authentication for a local development environment.

/**
 * TODO(developer): Uncomment and replace these variables before running the sample.
 */
// const projectId = 'YOUR_PROJECT_ID';
// const zone = 'europe-central2-b'
// const instanceName = 'YOUR_INSTANCE_NAME'

const compute = require('@google-cloud/compute');

async function getInstanceHostname() {
  const instancesClient = new compute.InstancesClient();

  const [instance] = await instancesClient.get({
    project: projectId,
    zone,
    instance: instanceName,
  });
  // If a custom hostname is not set, the output for instance.hostname will be undefined
  console.log(`Instance ${instanceName} has hostname: ${instance.hostname}`);
}

getInstanceHostname();

Python

Before trying this sample, follow the Python setup instructions in the Compute Engine quickstart using client libraries. For more information, see the Compute Engine Python API reference documentation.

To authenticate to Compute Engine, set up Application Default Credentials. For more information, see Set up authentication for a local development environment.

from google.cloud import compute_v1


def get_hostname(project_id: str, zone: str, instance_name: str) -> str:
    """
    Retrieve the hostname of given instance.

    Args:
        project_id: project ID or project number of the Cloud project you want to use.
        zone: name of the zone you want to use. For example: "us-west3-b"
        instance_name: name of the virtual machine to check.

    Returns:
        The hostname of an instance.
    """
    instance_client = compute_v1.InstancesClient()
    instance = instance_client.get(
        project=project_id, zone=zone, instance=instance_name
    )
    return instance.hostname

What's next

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