CloudFront Invalidation using Lambda via SNS

app.zip

s3-invalidation.js

console.log('Loading event');

var Q = require('q');
var aws = require('aws-sdk');
var cloudfront = new aws.CloudFront();

exports.handler = function (event, context) {
  _log('Received event: ', event);
  
  if (event.Records[0].EventSource == "aws:sns")
  {
    if(event.Records[0].Sns.Subject == "Amazon S3 Notification")
    { // overwrite S3 event object from payload
      event=JSON.parse(event.Records[0].Sns.Message);
    }
  }
  
  if(event.Records[0].eventSource != "aws:s3")
  {
    context.fail('unexpected event');
  }
  else
  {
    var bucket = event.Records[0].s3.bucket.name;
    var key = event.Records[0].s3.object.key;
    console.log('Bucket: '+bucket);
    console.log('Key: '+key);
  
    cloudfront.listDistributions({}, function (err, data) {
      var promises = [];
      if (err) {
        _log('Error: ', err);
        context.fail(err);
        return;
      }
  
      // Find a bucket which uses the backet as a origin.
      data.Items.map(function (distribution) {
        var deferred = Q.defer();
        var exists = false;
  
        distribution.Origins.Items.map(function (origin) {
          if (exists) return;
  
          if (origin.DomainName.indexOf(bucket) === 0) {
            exists = true;
            var name = distribution.DomainName;
            if (distribution.Aliases.Quantity > 0) {
              name = distribution.Aliases.Items[0];
            }
            console.log('Distribution: ' + distribution.Id + ' ('+ name + ')');
  
            // Parameters for a invalidation
            var params = {
              DistributionId : distribution.Id,
              InvalidationBatch : {
                CallerReference : '' + new Date().getTime(),
                Paths : {
                  Quantity : 1,
                  Items : [ '/'+key ]
                }
              }
            };
            _log('Params: ', params);
  
            // Invalidate
            cloudfront.createInvalidation(params, function (err, data) {
              if (err) {
                _log('Error: ', err);
                deferred.reject();
                return;
              }
              _log('Success: ', data.InvalidationBatch);
              deferred.resolve();
            });
          }
        });
        if (! exists) deferred.resolve();
        promises.push(deferred.promise);
      });
      Q.all(promises).then(function() {
        context.succeed('');
      });
    });
  }

  function _log(caption, object) {
    console.log(caption + JSON.stringify(object, true, '  '));
  }
};