Invalidates objects on CloudFront triggered by S3 event

s3-cloudfront-invalidation.js

/**
 * Invalidates objects on CloudFront triggered by S3 event
 * Runtime: Node.js 6.10
 */

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

// returns if the Bucket is used in the Distribution
var bucketIsUsed = (distribution, bucketName) => {
    return distribution.Origins.Items.some(function(origin) {
        return (origin.DomainName.indexOf(bucketName) === 0);
    });
};

// creates an invalidation batch and returns Promise
var invalidate = (distribution, objectKey) => {
    return cloudfront.createInvalidation({
        DistributionId: distribution.Id,
        InvalidationBatch: {
            CallerReference: '' + new Date().getTime(),
            Paths: {
                Quantity: 1,
                Items: [ '/' + objectKey ]
            }
        }
    }).promise();
};

exports.handler = (event, context, callback) => {
    var bucketName = event.Records[0].s3.bucket.name;
	var objectKey = event.Records[0].s3.object.key;
	console.log('Bucket Name: '+bucketName);
	console.log('Object Key: '+objectKey);
	
	const listDistributionsPromise = cloudfront.listDistributions({}).promise();
	
	listDistributionsPromise.then( (data) => {
		var distributions = data.DistributionList.Items;
		var usedDistributions = distributions.filter( (distribution) => {
		    // filter distributions by the bucket name
		    return bucketIsUsed(distribution, bucketName)
		});
		
		return usedDistributions;
	}).then( (usedDistributions) => {
	    return Promise.all(usedDistributions.map( (usedDistribution) => {
    	    // perform invalidation
    	    return invalidate(usedDistribution, objectKey);
	    }));
	}).then( (data) => {
	    // done
	    console.log('done!');
	    console.log(JSON.stringify(data));
	    context.done(null, '');
	}).catch( (err) => {
		console.error('Error: ', err);
		context.done('error', err);
	})
};