Simple AWS Lambda script to notify by SNS if a domain is expiring within 3 days

daily_whois_halil_im.js

// Simple AWS Lambda function to notify if the domain halil.im is expiring within 3 days.
// Tested on Node.js 6.10 runtime.
// * Create an SNS topic and an SNS subscription with the email you want to be notified
// * Create the function with a trigger of "CloudWatch Events - Schedule" with rate: 1 day
// * Provide the SNS topic ARN to the function as an environment variable
// * Create and attach a policy to the role of this function with sns:Publish on the SNS topic ARN
//   (logs:CreateLogGroup, logs:CreateLogStream & logs:PutLogEvents on a logs ARN should already be there)

/* eslint-env node,es6 */
/* eslint no-console: "off" */

'use strict';

const WHOIS_HOST = 'whois.nic.im';
const WHOIS_PORT = 43;
const DOMAIN = 'halil.im';
const SNS_TOPIC_ARN = process.env.sns_topic_arn;

const net = require('net');
const AWS = require('aws-sdk');
const SNS = new AWS.SNS({ apiVersion: '2010-03-31' });

function SNSpublish(subject, message, errorPrefix) {
  SNS.publish(
    {
      Subject: subject,
      Message: message,
      TopicArn: SNS_TOPIC_ARN,
    },
    (err) => {
      if (errorPrefix && err) {
        console.error(`${errorPrefix}: ${err}`);
      }
    }
  );
}

exports.handler = () => {
  let socket = new net.Socket();
  socket.setTimeout(10000);

  socket.connect(WHOIS_PORT, WHOIS_HOST, () => {
    socket.write(`${DOMAIN}\r\n`);
  });

  let received = '';
  socket.on('data', (chunk) => {
    received += chunk;
  });

  socket.on('timeout', () => {
    socket.destroy();
    console.error('The socket timed out');
  });

  socket.on ('error', (err) => {
    console.error(`Socket error: ${err}`);
  });

  socket.on('close', () => {
    if (!received) {
      console.error('No data received');
      SNSpublish('No data received', `No data received querying the domain ${DOMAIN}`);
      return;
    }

    // .im specific
    let matched = received.match(/Expiry Date: 0?(\d+)\/0?(\d+)\/(\d+)/mi);
    if (!matched) {
      const errTitle = "Couldn't detect the expiry date";
      const errMsg = `${errTitle}, the format might have changed. Received data:\n${received}`;
      console.error(errMsg);
      SNSpublish(errTitle, errMsg);
      return;
    }

    let [, day, month, year] = matched;
    let expiryDate = new Date(year, month - 1, day);
    let daysRemaining = Math.round((expiryDate.getTime() - Date.now()) / 86400000);
    if (daysRemaining <= 3) {
      SNSpublish(
        `${DOMAIN} is expiring in ${daysRemaining} days`,
        `The domain ${DOMAIN} is expiring in ${daysRemaining} days`,
        "Couldn't publish expiry notification"
      );
    }
  });
};