asg_notifications_lambda.js

var https = require('https');
var util = require('util');
var webhook = '/services/webhook';
var errorMessage = "ERROR";

exports.handler = function(event, context) {
    console.log(JSON.stringify(event, null, 2));
    console.log('From SNS:', event.Records[0].Sns.Message);

    var postData = {
        "channel": "#monitoring",
        "icon_emoji": ":cloud:",
    };

    var message = JSON.parse(event.Records[0].Sns.Message);

    postData.attachments = [{
         "text": message.Description,
         "title": "AWS ASG Notifications",
         "color": getStatusColor(message.Event),
    }];

    try {
        postData.attachments[0]["fields"] = [];
        for (var key of ['AutoScalingGroupName', 'Cause', 'Event', 'EC2InstanceId', 'Progress', 'StartTime']) {
            var field = {
                title: key,
                value: message[key],
                short: false
            };
            postData.attachments[0]["fields"].push(field);
        }
    } catch (err) {
        console.log("Message body was not a JSON payload");
    }
    
    var options = {
        method: 'POST',
        hostname: 'hooks.slack.com',
        port: 443,
        path: webhook
    };

    var req = https.request(options, function(res) {
      res.setEncoding('utf8');
      res.on('data', function (chunk) {
        context.done(null);
      });
    });
    
    req.on('error', function(e) {
      console.log('problem with request: ' + e.message);
    });    

    req.write(util.format("%j", postData));
    req.end();
};

String.prototype.contains = function(str, ignoreCase) {
  return (ignoreCase ? this.toUpperCase() : this)
    .indexOf(ignoreCase ? str.toUpperCase() : str) >= 0;
};

/*  returns a Slack color depending on the modulus event type. Crash should be red, deploy should be
 *  green, and everything else will be orange.
 */

var getStatusColor = function(messageEvent) {
  if(messageEvent.contains(errorMessage)) {
    return 'danger';
  } else {
    return 'warning';
  }
};