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IRIS

Description

CDN/Media Server infrastructure with the capability of resizing images on the fly. Built using the Serverless Framework.

Usage

There are three different types of URLs you can build to create your dynamically sized images:

Type URL
Original /path/to/image.jpg
Rectangle /300x250/path/to/image.jpg
Rectangle w/ command /300x250@max/path/to/image.jpg

Anatomy of the URL

/{width}x{height}@{command}/{path_to_original_image}

Valid commands

Command Description
max Preserving aspect ratio, resize the image to be as large as possible while ensuring its dimensions are less than or equal to the width and height specified. Sharp documentation on max
min Preserving aspect ratio, resize the image to be as small as possible while ensuring its dimensions are greater than or equal to the width and height specified. Sharp documentation on min

Limitations

  • width must be less than or equal to 1920
  • height must be less than or equal to 1080
  • Decimals are not allowed in the height and width

Requirements

Important: Be sure to set up proper AWS credentials on your machine, otherwise the Serverless deploy commands will fail.

Setup

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. We will use Docker to download Amazon Linux, install Node.js and developer tools, and build the extensions.

Run make dist

2. Provision AWS infrastructure with Serverless

The Serverless Framework was designed to provision your AWS Lambda Functions, Events and infrastructure Resources safely and quickly. This will take several minutes. Don't worry if it seems to hang, particularly during the Cloudfront setup.

Run serverless deploy

Note: You can specify a stage while deploying by using the --stage flag. e.g. serverless deploy --stage production. Defaults to dev if no --stage is set.

3. Add IndexDocument and ErrorDocument to S3

Next, we need to manually upload index.html, 404.html, and favicon.ico to our newly created S3 bucket:

  1. Go to the S3 Console
  2. Open our iris-{stage}-mediaserver-xxxxx bucket
  3. In the upper left, click the "Upload" button
  4. Upload the files inside of the ./etc/s3-default-documents directory. Be sure to make these public!

Automating this process is on the road map.

That's it!

We now have all of our AWS infrastructure in place for our media server, and the first version of the Resize Image function deployed.

Deploying changes to Lambda functions

The majority of deployments will be in maintaining the functions deployed to Lambda. Whenever changes are made to files inside of the ./lambda directory, we will need to repackage and deploy the changes.

This can be done by running the following commands:

  1. make dist
  2. serverless deploy --package

Serverless CLI Reference

https://serverless.com/framework/docs/providers/aws/cli-reference/

Quick Reference

Deploy to production

serverless deploy --stage production

For more, see Serverless CLI documentation for deploy

Remove provisioned infrastructure

serverless remove

For more, see Serverless CLI documentation for remove

Setting up a custom domain and SSL certificate

Cloudfront, by default, will issue a random domain name; something like abcde12345.cloudfront.net. Thankfully, it's possible to use your own domain name (e.g. cdn.example.com).

We can do this with a few changes to serverless.yml and then a new deployment:

  1. In the environment variables section, uncomment CERT_DOMAIN, CERT_VALIDATION_DOMAIN, and CDN_ARN
  2. Change CERT_DOMAIN. This will be the domain(s) that you want have SSL certs for. e.g. *.example.com or subdomain.example.com
  3. Change CERT_VALIDATION_DOMAIN. This is the root domain that you will receive a validation email at. Domain must match the above TLD. e.g. example.com
  4. In the Resources section, uncomment the CDNCert section, as well as the Aliases and ViewerCertificate options under the MediaCDN section
  5. sls deploy

During this step, Amazon will send an email to you with a link for you to click to validate your domain. If your CERT_VALIDATION_DOMAIN is example.com, they will send a validation email to all of the following addresses:

NOTE: The serverless deployment will hang until you validate your domain, so keep that in mind if you need to coordinate with other people during this step.

After the domain has been validated, the deployment will continue as normal. Your Cloudfront distribution will restart during this process, so it will probably take a number of minutes for the deployment to complete.

You should now be able to use your shiny new cdn.example.com domain!

AWS Services Used

  • Amazon API Gateway
  • Amazon Cloudfront
  • Amazon S3
  • AWS Lambda