art of a tutorial on greenido.wordpress.com to show the power of Apps script as a simple site monitor

apps_script_site_monitor_2.js

//
// The main logic to check the site and do a quick 2nd check in case we 
// did not get 200 as return code
//
function checkAndNotify(monitorObj, curCode) {
  var status = monitorObj.status;
  if (curCode === 200) {
    if (status === 503) {
       // Site was down previously but up on second check
       logToSheet(monitorObj.url, "The site is Up");
    }
    // We are cool
    return curCode;
  }
  
  // Site was up previously but is now down
  if (curCode === 503 ) {
    if (status === 200) {
      // Run another check after 1 minutes to prevent false positives
      quickCheck();
    }
    else if (status === 503 ) {
      // Site was down previously and is down again 
      quickCheck();
      logToSheet(monitorObj.url, "Process is Down");
    }
    return curCode;
  }

  Logger.log("WARN: We did not catch code: " + curCode + " - let's check why");
  return curCode;
}

//
// Log our alerts to the main sheet and get info from
// The 'Form' sheet in order to mute the alerts.
//
function logToSheet(url, message) {
  var formSheet = SpreadsheetApp.getActiveSpreadsheet().getSheets()[1];
  
  // We wish to see what is the last response from the 'mute alerts' form
  var toStopEmailsRow = formSheet.getLastRow();
  var toStopEmails = formSheet.getRange(toStopEmailsRow, 2).getValue();  
  
  // The logger sheet
  var sheet = SpreadsheetApp.getActiveSpreadsheet().getSheets()[0];
  var row   = sheet.getLastRow() + 1;    
  var time  = new Date();  
  sheet.getRange(row,1).setValue(time);
  sheet.getRange(row,2).setValue(message + " : " + url);
  
  var alert = "At: " + time + " Our site on: " + url + 
    " is " + message.toLowerCase() + 
    "  | To stop emails: http://bit.ly/please-stop-email-now";
  
  if (toStopEmails === "Yes") {
    Logger.log(alert + " But with no email");
  }
  else {
    // Send an email with the alert
    Logger.log(alert);
    MailApp.sendEmail(sheet.getRange("B3").getValue(), "Site " + message, alert);    
  }
}

//
// Let's check the site again to confirm that it's down
//
function secondCheck() {
  // first we clean all the triggers to keep our house clean
  var checksTriggers = ScriptApp.getProjectTriggers();
  for (var i=0; i< checksTriggers.length; i++) {
    if (checksTriggers[i].getHandlerFunction() == "secondCheck") {
      ScriptApp.deleteTrigger(checksTriggers[i]);
    }
  }
  // Back to our main function
  blogMonitor();
}

//
// Our const - you should put it at another file that contain all your
// configurations.
//
var HALFMinute = 30000;

// 
// Wait 30sec and check again
//
function quickCheck() {
  ScriptApp.newTrigger("secondCheck").timeBased().after(HALFMinute).create();
}