Invalidate CloudFront cache for static websites hosted on S3

example-event.json

{
   "Records":[
      {
         "eventVersion":"2.0",
         "eventSource":"aws:s3",
         "awsRegion":"us-west-2",
         "eventTime":"1970-01-01T00:00:00.000Z",
         "eventName":"ObjectCreated:Put",
         "userIdentity":{
            "principalId":"AIDAJDPLRKLG7UEXAMPLE"
         },
         "requestParameters":{
            "sourceIPAddress":"127.0.0.1"
         },
         "responseElements":{
            "x-amz-request-id":"C3D13FE58DE4C810",
            "x-amz-id-2":"FMyUVURIY8/IgAtTv8xRjskZQpcIZ9KG4V5Wp6S7S/JRWeUWerMUE5JgHvANOjpD"
         },
         "s3":{
            "s3SchemaVersion":"1.0",
            "configurationId":"testConfigRule",
            "bucket":{
               "name":"sourcebucket",
               "ownerIdentity":{
                  "principalId":"A3NL1KOZZKExample"
               },
               "arn":"arn:aws:s3:::sourcebucket"
            },
            "object":{
               "key":"HappyFace.jpg",
               "size":1024,
               "eTag":"d41d8cd98f00b204e9800998ecf8427e",
               "versionId":"096fKKXTRTtl3on89fVO.nfljtsv6qko"
            }
         }
      }
   ]
}

index.js

'use strict';

var Promise = require('bluebird');
var _ = require('lodash');
var Invalidation = require('./lib/Invalidation');
var AWS = require('aws-sdk');

var handle = function (event, context) {
  var cloudfront = new AWS.CloudFront();
  var s3 =  new AWS.S3();
  var s3Config = {
    Bucket: event.Records[0].s3.bucket.name,
    Key: '_my_cloudfront_config.json'
  };

  s3.getObject(s3Config, function (err, configObject) {
    if (err) {
      throw err;
    } else {
      var config = JSON.parse(configObject.Body.toString('utf8'));

      console.log(config);
      var invalidationPromises = _.map(event.Records, function (record) {
        var invalidation = new Invalidation(config, record);

        return invalidation.create(cloudfront);
      });

      Promise.all(invalidationPromises).then(function () {
        context.done();
      });
    }
  });
};

module.exports.handle = handle;

Invalidation.js

'use strict';

var crypto = require('crypto');
var path = require('path');
var Promise = require('bluebird');

var Invalidation = function (config, s3EventRecord) {
  this.record = s3EventRecord;

  this.config = config;
  this.resolver = Promise.pending();
};

Invalidation.prototype.params = function () {
  var refHash = crypto.createHash('md5');
  var s3Object = this.record.s3.object;
  var reference = s3Object.key + s3Object.eTag;
  var paths = this.paths();

  refHash.update(reference);
  var invalidationParams = {
    DistributionId: this.config.distributionId,
    InvalidationBatch: {
      CallerReference: refHash.digest('hex'),
      Paths: {
        Quantity: paths.length,
        Items: paths
      }
    }
  };

  console.log(invalidationParams.InvalidationBatch.Paths);

  return invalidationParams;
};

Invalidation.prototype.paths = function () {
  var s3ObjectKey = this.record.s3.object.key;
  var dirname = path.dirname(s3ObjectKey);

  if (path.basename(s3ObjectKey) === 'index.html') {
    if (dirname === '.') {
      dirname = '';
    }
    return [
      '/' + s3ObjectKey,
      path.normalize('/' + dirname + '/'),
      '/' + dirname
    ];
  } else {
    return ['/' + s3ObjectKey];
  }
};

Invalidation.prototype.create = function (cloudFrontDriver) {
  var resolver = this.resolver;

  cloudFrontDriver.createInvalidation(this.params(), function (err, data) {
    if (err) {
      resolver.reject(err);
    } else {
      resolver.fulfill(data);
    }
  });

  return resolver.promise;
};

module.exports = Invalidation;