yet another CloudWatch-to-Slack AWS Lambda function

slack-aws-lambda.js

const https = require('https');
const url = require('url');

const slack_url = ''; // put your slack webhook URL here

const slack_req_opts = url.parse(slack_url);
slack_req_opts.method = 'POST';
slack_req_opts.headers = {'Content-Type': 'application/json'};

exports.handler = function(event, context) {
	(event.Records || []).forEach(function (rec) {
		if (rec.Sns) {
			var req = https.request(slack_req_opts, function (res) {
				if (res.statusCode === 200) {
					context.succeed('posted to Slack');
				} else {
					context.fail('status code: ' + res.statusCode);
				}
			});

			req.on('error', function(e) {
				context.fail(e.message);
			});

			var payload = {
				username: 'Amazon AWS'  
			};

			try {
				var m = JSON.parse(rec.Sns.Message);

				var color =
				  (m.NewStateValue.toLowerCase() == 'ok') ? '#2AB27B' :
				  (m.NewStateValue.toLowerCase() == 'alarm') ? '#F85900' :
				  '#E8E8E7';

				payload.text = '_Alarm status changed:_ ' + m.OldStateValue + ' → *' + m.NewStateValue + '*';
				payload.attachments = [
  				{
  					title_link: 'https://console.aws.amazon.com/cloudwatch/home',
  					title: m.AlarmDescription,
  					text: m.NewStateReason,
  					color: color,
  					footer: m.AlarmName + ' - ' + m.Trigger.Namespace,
  					ts: Math.round(parseInt(Date.parse(m.StateChangeTime)) / 1000),
  					fields: m.Trigger.Dimensions.map(function(i) { return { title: i.name, value: i.value, short: true }; })
  				},
				];
			} catch (e) {
				payload.text = rec.Sns.Message;
				console.log(e);
			}

			req.write(JSON.stringify(payload));
			req.end();
		}
	});
};