from https://medium.com/@milanaleksic/using-aws-lambda-to-verify-uptime-5a459fc3bef6#.mz46smtde

siteuptime.js

'use strict';
var aws = require('aws-sdk');
var https = require('https');
var ses = new aws.SES();
var processingContext = {
    noOfSuccesses: 0, 
    failures: [],
    endpoints: [
    {url: "https://www.test.com", statusCode: 200},
    {url: "https://www.test2.com", statusCode: 200}
    ]
};
exports.handler = function (event, context) {
    var processingContextRunning = JSON.parse(JSON.stringify(processingContext));
    processingContextRunning.nodeJsContext = context;
    callEndpoints(processingContextRunning);
};
function callEndpoints(processingContext) {
    var endpoint = processingContext.endpoints.shift();
    if (endpoint) {
        https
            .get(endpoint.url, processOK(endpoint, processingContext))
            .on('error', processError(endpoint, processingContext));
    }
}
function processOK(endpoint, processingContext) {
    return function(result) {
        if (result.statusCode == endpoint.statusCode) {
            console.log(["Site ", endpoint.url, " seems OK"].join(""));
            processingContext.noOfSuccesses++;
        } else {
            var msg = ["Site ", endpoint.url, " failed, statusCode=", result.statusCode, ", expected: ", endpoint.statusCode].join("");
            console.log(msg);
            processingContext.failures.push(msg);
        }
        nextCall(processingContext);
    };
}
function processError(endpoint, processingContext) {
    return function(err) {
        var msg = [
            "Site ", 
            endpoint.url,
            " failed with error: ",
            err.message]
            .join("");
        console.log(msg);
        processingContext.failures.push(msg);
    };
}
function nextCall(processingContext) {
    if (processingContext.endpoints.length > 0) {
        callEndpoints(processingContext);
    } else {
        if (processingContext.failures.length>0) {
            sendEmail(processingContext);
        } else {
            processingContext.nodeJsContext
            .done([
                "Failures: ", 
                processingContext.noOfFailures, 
                ", successes: ", 
                processingContext.noOfSuccesses
            ].join(""));
        }
    }
}
function sendEmail(processingContext) {
    ses.sendEmail({
        Destination: {
            ToAddresses: [
            "alarmemail@gmail.com"
            ]
        },
        Message: {
            Subject: {
                Data: "AWS Lambda site check failed",
                Charset: 'UTF-8'
            },
            Body: {
                Text: {
                    Data: ["Failures encountered: ", processingContext.failures].join("\n"),
                    Charset: 'UTF-8'
                }
            }
        },
        Source: "alarmemail@gmail.com"
    }, function (err, data) {
        if (err) {
            console.log(err, err.stack);
            processingContext.nodeJsContext.fail('Internal Error: The email could not be sent.');
        } else {
            console.log("Email sent")
            processingContext.nodeJsContext.done('Email sent');
        }
    });
}