Serverless Image Resizing

Description

Resizes images on the fly using Amazon S3, AWS Lambda, and Amazon API Gateway. Using a conventional URL structure and S3 static website hosting with redirection rules, requests for resized images are redirected to a Lambda function via API Gateway which will resize the image, upload it to S3, and redirect the requestor to the resized image. The next request for the resized image will be served from S3 directly.

Usage

1. Build the Lambda function

   The Lambda function uses sharp for image resizing which requires native extensions. In order to run on Lambda, it must be packaged on Amazon Linux. You can accomplish this in one of two ways:

   • Upload the contents of the lambda subdirectory to an Amazon EC2 instance running Amazon Linux and run npm install, or

   • Use the Amazon Linux Docker container image to build the package using your local system. This repo includes Makefile that will download Amazon Linux, install Node.js and developer tools, and build the extensions using Docker. Run make all.

2. Deploy the CloudFormation stack (see last section for manual deployment)

   Run bin/deploy to deploy the CloudFormation stack. It will create a temporary Amazon S3 bucket, package and upload the function, and create the Lambda function, Amazon API Gateway RestApi, and an S3 bucket for images via CloudFormation.

   The deployment script requires the AWS CLI version 1.11.19 or newer to be installed.

3. Test the function

   Upload an image to the S3 bucket and try to resize it via your web browser to different sizes, e.g. with an image uploaded in the bucket called image.png:

   • http://[BucketWebsiteHost]/300x300/path/to/image.png
   • http://[BucketWebsiteHost]/90x90/path/to/image.png
   • http://[BucketWebsiteHost]/40x40/path/to/image.png

   You can find the BucketWebsiteUrl in the table of outputs displayed on a successful invocation of the deploy script.

4. (Optional) Restrict resize dimensions

   To restrict the dimensions the function will create, set the environment variable ALLOWED_DIMENSIONS to a string in the format (HEIGHT)x(WIDTH),(HEIGHT)x(WIDTH),....

   For example: 300x300,90x90,40x40.

Manual Deployment

More information at https://aws.amazon.com/blogs/compute/resize-images-on-the-fly-with-amazon-s3-aws-lambda-and-amazon-api-gateway/

<RoutingRules>
    <RoutingRule>
        <Condition>
            <KeyPrefixEquals/>
            <HttpErrorCodeReturnedEquals>404</HttpErrorCodeReturnedEquals>
        </Condition>
        <Redirect>
            <Protocol>https</Protocol>
            <HostName>__YOUR_API_HOSTNAME_HERE__</HostName>
            <ReplaceKeyPrefixWith>prod/resize?key=</ReplaceKeyPrefixWith>
            <HttpRedirectCode>307</HttpRedirectCode>
        </Redirect>
    </RoutingRule>
</RoutingRules>

• Create destination bucket

• Give destination bucket static website permission and make it public

• Add redirection to the static hosting configuration

• Create lambda

• Give read permissions to source bucket (where the original files exist)

• Give read and write permission to destination bucket (where the thumbnails are going to live)

• Configure the following properties in the lambda

SOURCE_BUCKET

Where the originals reside

THUMBNAIL_DESTINATION_BUCKET

Where the thumbnails are going to reside

URL

The cloud front URL

VIDEO_SCREENSHOT_TIME_MARK (Optional)

At what second of the video the screenshot is taken, defaults to 3

DEFAULT_VIDEO_CHUNK_SIZE

The default chunk size of the video (this is a chunk of the video needed for metadata) defaults to 10200

License

This reference architecture sample is licensed under Apache 2.0.