Issue with node.js app stopping on AWS

I have a node.js app that pings a url and then sends a message to Slack if it gets an error code. It works fine for two days but then it just stops working. I'm using Screen to keep it running but it still seems to stop. Any help would be greatly appreciated.

The code is below:

var request = require("request")
var Hapi = require('hapi');
var Slack = require('slack-node');
var h = 0;
var s = 0;
var e = 0;

function onlineBooking(){
request({
    url: "http://example.com",
    json: true
}, function (error, response, body) {

    if (!error && response.statusCode === 200) {

        // 'if/else' checks that it receives an up respsose four times in a row 
        // the variable e is increased by .25 for every 200(ok response) until e reaches 1
        // it will then send a message that the server is up
        if(e < 1  && response.statusCode === 200){
            setTimeout(function () {
           console.log(response.statusCode) // Print the response code
            e =e+0.25;
            }, 6000); // 6 seconds delay between each response 
        }

    else {
          while(h == 0){
        console.log(response.statusCode) // Print the response code
        console.log("********************")
        slackReviewBot("Website :robot_face: ", response.statusCode + " - OK", "http://example.com", "");
            h++;
            s = 0; 
          } 
        }// end of else
    }// end of if
    else {
        console.log(response.statusCode) // Print the response code
        e = 0;
        setTimeout(function () {  
        while(s == 0){

        console.log(response.statusCode) // Print the response code
        console.log("********************")
        slackReviewBot("Website :robot_face: ", response.statusCode, "http://example.com", "");
            s++;
            h=0;
        }}, 3000);
    } // end of else

})

}

// sets the loop for checking every 7 seconds

setInterval(function(){

    onlineBooking();

}, 7000); 


//  this function sends server name, a message and url to slack
function slackReviewBot(servername, body, urls, bod) {

var time = require('time');
// Create a new Date instance
var now = new time.Date();
now.setTimezone("Europe/London");

    var bo = body; 
    var bod = bod;
    var urls = urls;
    var sname = servername; 
    // you'll need to replace the slack webhook below
    // you'll find info on webhooks here https://api.slack.com/incoming-webhooks
    var webhook_url = 'https://hooks.slack.com/services/xxxxxxxxxxxxxxxxxxxxxx';
    slack = new Slack();
    slack.setWebhook(webhook_url);

        slack.webhook({
        channel: "#server-uptime",
        username: "Server:",
        icon_emoji: "http://4.bp.blogspot.com/-mYCTaPOu-60/VK98X5CJEyI/AAAAAAAAApM/0oplbclvnUY/s1600/unnamed.png",
        text: " " + "\n" + 
            "*" + sname + " * " + "\n" +
            "Status: " + bo + "\n" +
            now + "\n" +
            "Check the status here: " + urls + "\n" 

        }, function(err, response) {      
        console.log(response);
        }); 
}



// below is so you can send a test json object to the server
// http POST localhost:1337/jsonpost test=Test 
// you'll get a slack message letting you know the server is running
var server = new Hapi.Server();
server.connection({
    port: 1337
});

exports.add = function(i, j) {
    return i + j;
};

//  Slack function for sending the test reply
function slackReviewBot2(testserver) {
    testserver = testserver;
      // you'll need to replace the slack webhook below
    // you'll find info on webhooks here https://api.slack.com/incoming-webhooks
    var webhook_url = 'https://hooks.slack.com/services/xxxxxxxxxxxxxxxxxxxxxxxxxx';
    slack2 = new Slack();
    slack2.setWebhook(webhook_url);


        slack.webhook({
        channel: "#server-uptime",
        username: "Server-Test-Reply:",
        icon_emoji: "http://www.wonderfulwebsites.ie/logo.png",
        text: ":star: :star: :star: :star: :star:" + "\n" + 
            "\n" + 
            "Sever is up and running!!!"

        }, function(err, response) {

        console.log(response);
        });
}


// take the json object for testing
server.route({
  method: 'POST'
, path: '/jsonpost',
handler: function(req, reply) {

     var review = {
      userName: req.payload.userName
      }
            //passes the review to the slackbot function 
            slackReviewBot2(review.userName);
            reply("Received");
    } 
});

// prints a server running message 
server.start(function(){
    console.log('server running at: ', server.info.url);
});

You can find a post explaining how it works below http://codingyoda.com/slack-pinging-tool.php