Poll GCE instance to make sure it hasn't died (or been pre-empted)...

gce-instance-pollster.js

var Compute = require('@google-cloud/compute');
var {poll} = require('@nkashy1/pollster');
var twilio = require('twilio');

// START gcp-related setup
const gcpProject = process.env.GOOGLE_CLOUD_PROJECT
const gcpSacred = process.env.GOOGLE_APPLICATION_CREDENTIALS
const gceZone = process.env.GOOGLE_COMPUTE_ZONE;
const gceInstance = process.env.GOOGLE_COMPUTE_INSTANCE;

if (!gcpProject || !gcpSacred || !gceZone || !gceInstance) {
    let message = (
            'One of these environment variables is undefined:\n' +
            `GOOGLE_CLOUD_PROJECT: ${!!gcpProject}\n` +
            `GOOGLE_APPLICATION_CREDENTIALS: ${!!gcpSacred}\n` +
            `GOOGLE_COMPUTE_ZONE: ${!!gceZone}\n` + 
            `GOOGLE_COMPUTE_INSTANCE: ${!!gceInstance}\n`
            );
    throw new Error(message);
}

var gce = new Compute({
    projectId: gcpProject,
    keyFilename: gcpSacred
});
// END gcp-related setup

// START twilio-related setup
var twilioAccountSid = process.env.TWILIO_ACCOUNT_SID;
var twilioAuthToken = process.env.TWILIO_AUTH_TOKEN;
var twilioPhoneNumber = process.env.TWILIO_PHONE_NUMBER;
var notificationPhoneNumber = process.env.NOTIFICATION_PHONE_NUMBER;

if (!twilioAccountSid || !twilioAuthToken || !twilioPhoneNumber || !notificationPhoneNumber) {
    let message = (
            'The following environment variables should be defined:\n' +
            `TWILIO_ACCOUNT_SID: ${!!twilioAccountSid}\n` +
            `TWILIO_AUTH_TOKEN: ${!!twilioAuthToken}\n` +
            `TWILIO_PHONE_NUMBER: ${!!twilioPhoneNumber}\n` +
            `NOTIFICATION_PHONE_NUMBER: ${notificationPhoneNumber}\n`
            );
    throw new Error(message);
}

var twilioClient = new twilio(twilioAccountSid, twilioAuthToken);
// END twilio-related setup

function smsSignaller(twilioClient, twilioPhoneNumber, notificationPhoneNumber, message) {
    function sendSignal(err) {
        if (!!err) {
            console.error(err);
            process.exit(1);
        }

        return twilioClient.messages.create({
            body: message,
            to: notificationPhoneNumber,
            from: twilioPhoneNumber
        }, function(err, message) {
            if (!!err) {
                console.error(err);
                process.exit(1);
            }
            console.log(
                    `Message sent: ${message.sid}`);
            process.exit(0);
        });
    }

    return sendSignal;
}

function vmStatusPredicate(alarmingStatuses) {
    function predicate(cb) {
        console.log(`${Date.now()} - polling status of ${gceInstance}...`);
        let vm = gce.zone(gceZone).vm(gceInstance);
        return vm.exists((err, existsp) => {
            if (!!err) {
                return cb(err);
            }

            if (!existsp) {
                console.log(`${gceInstance} non-existent`);
                return cb(null, true)
            }

            return vm.getMetadata((err, metadata, apiResponse) => {
                if (!!err) {
                    return cb(err);
                }

                let vmStatus = apiResponse.status;
                console.log(`Status: ${vmStatus}`);

                if (alarmingStatuses[vmStatus]) {
                    return cb(null, true);
                }

                return cb(null, false);
            });
        });
    }

    return predicate;
}

let watchStatuses = {
    STOPPING: true,
    TERMINATED: true
};
console.log(`Watching instance ${gceInstance} in zone ${gceZone} for the following statuses: ${Object.keys(watchStatuses).join(', ')}`);
poll(
        vmStatusPredicate(watchStatuses),
        5000,
        Infinity,
        smsSignaller(
            twilioClient,
            twilioPhoneNumber,
            notificationPhoneNumber,
            `Instance down: ${gceInstance}`)
    );

package.json

{
  "name": "@nkashy1/gce-monitor",
  "version": "0.0.1",
  "description": "Monitor state of GCE resources",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "nkashy1",
  "license": "Apache-2.0",
  "dependencies": {
    "@google-cloud/compute": "^0.10.0",
    "@nkashy1/pollster": "0.0.3",
    "twilio": "^3.15.1"
  }
}