Hook AWS notifications into Slack with a Lambda function
inopinatus

We have AWS RDS instances that send lifecycle notifications to an SNS topic. This was ending up in email, but I prefer to receive notifications in a Slack channel. Fortunately they are easy to integrate using AWS Lambda and Slack’s webhooks.

Here’s the Lambda function I’m using*, which parses the message object (if it can) and formats the notifications before posting.

console.log('Loading function');

const https = require('https');
const url = require('url');
const slack_url = 'https://hooks.slack.com/services/...';
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) {
        console.log('problem with request: ' + e.message);
        context.fail(e.message);
      });

      var text_msg = JSON.stringify(rec.Sns.Message, null, '  ');
      try {
        var msg_data = [];
        var parsed = JSON.parse(rec.Sns.Message);
        for (var key in parsed) {
          msg_data.push(key + ': ' + parsed[key]);
        }
        text_msg = msg_data.join("\n");
      } catch (e) {
        console.log(e);
      }

      var params = {
        attachments: [{
          fallback: text_msg,
          pretext: rec.Sns.Subject,
          color: "#D00000",
          fields: [{
            "value": text_msg,
            "short": false
          }]
        }]
      };
      req.write(JSON.stringify(params));

      req.end();
    }
  });
};

Note: the following links will require both AWS and Slack logins.

To do it yourself, create the webhook in Slack. Then publish the code above as a Lambda function in your AWS account (a basic execution role will be fine). Update line 5 with your own webhook URL. Have RDS notify a SNS topic and subscribe the Lambda function to that topic.

You can check the integration using Lambda’s standard SNS test event. For an end-to-end & event parsing test I suggest creating and deleting a RDS snapshot.