automatically register GCE instances in google cloud DNS?

Question

How do I have my GCE instances register with an internal GCP DNS zone? Is there a built in way to do this?

Edit: looks like I can do this https://cloud.google.com/sdk/gcloud/reference/dns/record-sets/transaction/add

Answer 1

For a full guide on this, check out Google Cloud Platform in Action .

You can use the Cloud DNS API to register the instance, which is pretty straight forward. I think the part that isn't well documented would be how to get the right IP address and such in a start-up script.

The following code snippet has some helpers in Node.js that pull down instance names, zones, and IP addresses which you can then use to register with Cloud DNS.

const request = require('request');

const metadataUrl = 'http://metadata.google.internal/computeMetadata/v1/';
const metadataHeader = {'Metadata-Flavor': 'Google'};

const getMetadata = (path) => {
  const options = {
    url: metadataUrl + path,
    headers: metadataHeader
  };
  return new Promise((resolve, reject) => {
    request(options, (err, resp, body) => {
      resolve(body) ? err === null : reject(err);
    });
  });
};

const getInstanceName = () => {
  return getMetadata('instance/name');
};

const getInstanceZone = () => {
  return getMetadata('instance/zone').then((data) => {
    const parts = data.split('/');
    return parts[parts.length-1];
  })
};

const getInstanceIp = () => {
  const path = 'instance/network-interfaces/0/access-configs/0/external-ip';
  return getMetadata(path);
};

const getInstanceDetails = () => {
  const promises = [getInstanceName(), getInstanceZone(), getInstanceIp()];
  return Promise.all(promises).then((data) => {
    return {
      name: data[0],
      zone: data[1],
      ip: data[2]
    };
  });
};

So then in Cloud DNS, you could register using these helpers by doing something like the following (note this was written using an early version of the DNS library -- you can install it by running npm install @google-cloud/dns@0.6.1 ).

const dns = require('@google-cloud/dns')({
  projectId: 'your-project-id'
});
const zone = dns.zone('mydomain-dot-com');

getInstanceDetails().then((details) => {
  return zone.record('a', {
    name: [details.name, details.zone].join('-') + '.mydomain.com.',
    data: details.ip,
    ttl: 86400
  });
}).then((record) =>{
  return zone.createChange({add: record});
}).then((data) => {
  const change = data[0];
  console.log('Change created at', change.metadata.startTime,
              'as Change ID', change.metadata.id);
  console.log('Change status is currently', change.metadata.status);
});

Answer 2

It sounds like you want an internal DNS registration, in which case this happens automatically. See https://cloud.google.com/compute/docs/internal-dns .

For example, if you create an instance named "instance-1", it will be automatically resolvable from any instance in the same network and project as either instance-1 or the FQDN: [HOST_NAME].c.[PROJECT_ID].internal .

Note: automatic external DNS registration is now in alpha: https://issuetracker.google.com/issues/35904549