Goal

In this post, I will show you how to use Amazon S3 Object Lambda to resize images on the fly. The  Serverless Framework will be used to define the Infrastructure as Code and to simplify the deployment. Sharp will be used to resize the images. Lambda will be written using the Node.js 14x  Lambda runtime

What’s Amazon S3 Object Lambda

One of the most common Lambda patterns is to transform data stored inside Amazon S3. Generally, a lambda function is invoked after a file has been uploaded. Lambda would retrieve that file, apply any needed transformation (e.g. converting type of file) and store the result in S3.

That pattern was working well, however, it would require some work done onto a file despite that being accessed in the future or not.

If you needed to convert a file on the fly you should have created a Lambda function, invoke it via Amazon API GW and wait for the lambda to perform the transformation.

AWS has recently introduced  Amazon S3 Object Lambda in a good post by Danilo Poccia. S3 Object Lambda allows creating a Lambda directly connected to the S3 bucket (using  S3 Access Points) that is automatically invoked when retrieving the object from S3!

That means that our application needs only to send an S3 Get Object request to retrieve the original or transformed data

Also, a very important peculiarity of using Amazon S3 Object Lambda it’s that the file you want to retrieve doesn’t need to exist on S3! We will make use of this for our scenario

_Note: High-level AWS CLI S3 commands (e.g. _aws s3 cp_) don’t currently support S3 Object Lambda, instead we need to use low-level S3 API commands (e.g. __aws s3api get-object)_

Common Use Cases

In his post, Danilo highlighted the most common use cases for Amazon S3 Object Lambda:

• Converting across data formats (e.g. XML to JSON)
• Compressing or decompressing files on the fly
• Resizing images on the fly (our use case!)
• Many more (left to the devs’ creativity)

#aws-lambda #serverless #aws-s3 #aws