AWSLambdaSlackNotification

index.js

var event = {
  "Records": [
    {
      "EventVersion": "1.0",
      "EventSubscriptionArn": "arn:aws:sns:EXAMPLE",
      "EventSource": "aws:sns",
      "Sns": {
        "SignatureVersion": "1",
        "Timestamp": "1970-01-01T00:00:00.000Z",
        "Signature": "EXAMPLE",
        "SigningCertUrl": "EXAMPLE",
        "MessageId": "95df01b4-ee98-5cb9-9903-4c221d41eb5e",
        // "Message": "Hello from SNS!",
        "Message": '{"configurationItemDiff":{"changedProperties":{},"changeType":"CREATE"},"configurationItem":{"relatedEvents":[],"relationships":[],"configuration":{"alarmName":"awsapplicationelb-app-SampleAppELB-4cfa0c9ece494773-High-HTTP-4XX","alarmArn":"arn:aws:cloudwatch:ap-northeast-1:916766174167:alarm:awsapplicationelb-app-SampleAppELB-4cfa0c9ece494773-High-HTTP-4XX","alarmDescription":"Created from EC2 Console","alarmConfigurationUpdatedTimestamp":1498004451605,"actionsEnabled":true,"alarmActions":["arn:aws:sns:ap-northeast-1:916766174167:config-topic"],"insufficientDataActions":[],"metricName":"HTTPCode_Target_4XX_Count","namespace":"AWS/ApplicationELB","statistic":"Average","dimensions":[{"name":"LoadBalancer","value":"app/SampleAppELB/4cfa0c9ece494773"}],"period":60,"evaluationPeriods":1,"threshold":10.0,"comparisonOperator":"GreaterThanOrEqualToThreshold","okactions":[]},"supplementaryConfiguration":{},"tags":{},"configurationItemVersion":"1.2","configurationItemCaptureTime":"2017-06-21T00:32:13.684Z","configurationStateId":1498005133684,"awsAccountId":"916766174167","configurationItemStatus":"ResourceDiscovered","resourceType":"AWS::CloudWatch::Alarm","resourceId":"awsapplicationelb-app-SampleAppELB-4cfa0c9ece494773-High-HTTP-4XX","resourceName":"awsapplicationelb-app-SampleAppELB-4cfa0c9ece494773-High-HTTP-4XX","ARN":"arn:aws:cloudwatch:ap-northeast-1:916766174167:alarm:awsapplicationelb-app-SampleAppELB-4cfa0c9ece494773-High-HTTP-4XX","awsRegion":"ap-northeast-1","availabilityZone":"Not Applicable","configurationStateMd5Hash":"","resourceCreationTime":null},"notificationCreationTime":"2017-06-21T00:32:13.879Z","messageType":"ConfigurationItemChangeNotification","recordVersion":"1.2"}',
        "MessageAttributes": {
          "Test": {
            "Type": "String",
            "Value": "TestString"
          },
          "TestBinary": {
            "Type": "Binary",
            "Value": "TestBinary"
          }
        },
        "Type": "Notification",
        "UnsubscribeUrl": "EXAMPLE",
        "TopicArn": "arn:aws:sns:EXAMPLE",
        "Subject": "TestInvoke"
      }
    }
  ]
};

var context = {};
var callback = function(err, data) {
    return;
};

var myLambda = require('./lambda');
myLambda.handler(event, context, callback);

lambda.js

`use strict`

const AWS = require('aws-sdk');
const url = require('url');
const https = require('https');

// The base-64 encoded, encrypted key (CiphertextBlob) stored in the kmsEncryptedHookUrl environment variable
const kmsEncryptedHookUrl = process.env.kmsEncryptedHookUrl;
// The Slack channel to send a message to stored in the slackChannel environment variable
// const slackChannel = process.env.slackChannel;
const slackChannel = "fr_aws";
let hookUrl;
hookUrl="";

function postMessage(message, callback) {
    const body = JSON.stringify(message);
    const options = url.parse(hookUrl);
    options.method = 'POST';
    options.headers = {
        'Content-Type': 'application/json',
        'Content-Length': Buffer.byteLength(body),
    };

    const postReq = https.request(options, (res) => {
        const chunks = [];
        res.setEncoding('utf8');
        res.on('data', (chunk) => chunks.push(chunk));
        res.on('end', () => {
            if (callback) {
                callback({
                    body: chunks.join(''),
                    statusCode: res.statusCode,
                    statusMessage: res.statusMessage,
                });
            }
        });
        return res;
    });

    postReq.write(body);
    postReq.end();
}

function processEvent(event, callback) {
    const message = JSON.parse(event.Records[0].Sns.Message);
    // const alarmName = message.AlarmName;
    // var oldState = message.OldStateValue;
    // const newState = message.NewStateValue;
    // const reason = message.NewStateReason;
    // const slackMessage = {
    //     channel: slackChannel,
    //     text: `${alarmName} state is now ${newState}: ${reason}`,
    // };

    // const message = event.Records[0].Sns.Message;
    // const slackMessage = {
    //     channel: slackChannel,
    //     text: `${message}`
    // };

    const messageType = message.messageType;
    var text = `messageType: ${messageType}\r\n`;
    switch(messageType){
        case "ConfigurationItemChangeNotification":
            text += `Type:${message.configurationItemDiff.changeType}\r\n resourceName:${message.configurationItem.resourceName}`
        break;
        default:
        break;
    }
    const slackMessage = {
        channel: slackChannel,
        text: `${text}`
    };

    postMessage(slackMessage, (response) => {
        if (response.statusCode < 400) {
            console.info('Message posted successfully');
            callback(null);
        } else if (response.statusCode < 500) {
            console.error(`Error posting message to Slack API: ${response.statusCode} - ${response.statusMessage}`);
            callback(null);  // Don't retry because the error is due to a problem with the request
        } else {
            // Let Lambda retry
            callback(`Server error when processing message: ${response.statusCode} - ${response.statusMessage}`);
        }
    });
}


exports.handler = (event, context, callback) => {
    if (hookUrl) {
        // Container reuse, simply process the event with the key in memory
        processEvent(event, callback);
    } else if (kmsEncryptedHookUrl && kmsEncryptedHookUrl !== '<kmsEncryptedHookUrl>') {
        const encryptedBuf = new Buffer(kmsEncryptedHookUrl, 'base64');
        const cipherText = { CiphertextBlob: encryptedBuf };

        const kms = new AWS.KMS();
        kms.decrypt(cipherText, (err, data) => {
            if (err) {
                console.log('Decrypt error:', err);
                return callback(err);
            }
            hookUrl = `https://${data.Plaintext.toString('ascii')}`;
            processEvent(event, callback);
        });
    } else {
        callback('Hook URL has not been set.');
    }
};