# Amazon S3 with S3 Object Lambda - Returns image thumbnail from S3

The SAM template deploys a Lambda function, an S3 bucket, an S3 Access Point, and an S3 Object Lambda Access Point. This application uses S3 Object Lambda to return a thumbnail version of an image in S3.

Learn more about this pattern at Serverless Land Patterns: [https://serverlessland.com/patterns/s3-object-lambda](https://serverlessland.com/patterns/s3-object-lambda)

Important: this application uses various AWS services and there are costs associated with these services after the Free Tier usage - please see the [AWS Pricing page](https://aws.amazon.com/pricing/) for details. You are responsible for any AWS costs incurred. No warranty is implied in this example.

## Requirements

* [Create an AWS account](https://portal.aws.amazon.com/gp/aws/developer/registration/index.html) if you do not already have one and log in. The IAM user that you use must have sufficient permissions to make necessary AWS service calls and manage AWS resources.
* [AWS CLI](https://docs.aws.amazon.com/cli/latest/userguide/install-cliv2.html) installed and configured
* [Git Installed](https://git-scm.com/book/en/v2/Getting-Started-Installing-Git)
* [AWS Serverless Application Model](https://docs.aws.amazon.com/serverless-application-model/latest/developerguide/serverless-sam-cli-install.html) (AWS SAM) installed

## Deployment Instructions

1. Create a new directory, navigate to that directory in a terminal and clone the GitHub repository:
    ``` 
    git clone https://github.com/aws-samples/serverless-patterns
    ```
1. Change directory to the pattern directory:
    ```
    cd s3-object-lambda
    ```
1. From the command line, use AWS SAM to build and deploy the AWS resources for the pattern as specified in the template.yml file:
    ```
    sam build
    sam deploy --guided
    ```
1. During the prompts:
    * Enter a stack name
    * Enter the desired AWS Region
    * Allow SAM CLI to create IAM roles with the required permissions.

    Once you have run `sam deploy --guided` mode once and saved arguments to a configuration file (samconfig.toml), you can use `sam deploy` in future to use these defaults.

1. Note the outputs from the SAM deployment process. These contain the resource names and/or ARNs which are used for testing.

## How it works

When a request is made to the S3 Object Lambda Access Point, the Lambda function is invoked. Within the Lambda function code, the getObjectContext property contains the following useful information:

1. inputS3Url: a [presigned URL](https://docs.aws.amazon.com/AmazonS3/latest/userguide/ShareObjectPreSignedURL.html) that the function can use to download the original object from the supporting Access Point. In this way, the Lambda function does not need to have S3 read permissions to retrieve the original object and can only access the object processed by each invocation.
1. outputRoute, outputToken: used to send back the modified object using the [WriteGetObjectResponse](https://docs.aws.amazon.com/AmazonS3/latest/API/API_WriteGetObjectResponse.html) API.

The function uses the provided presigned URL to retrieve the requested image from S3 using [axios](https://www.npmjs.com/package/axios). The function resizes the image using [sharp](https://www.npmjs.com/package/sharp). Then the function returns a thumbnail version of the image back to S3 Object Lambda.

## Testing

Run the following S3 CLI command to upload two example images to the S3 bucket (example1.jpg, example2.jpg). Note, you must edit the {S3BucketName} placeholder with the name of the S3 Bucket. This is provided in the stack outputs.

```bash
aws s3 cp './images/' s3://{S3BucketName} --recursive
```

Run the following S3 CLI commands to download a thumbnail version of an example image. Note, you must edit the {S3ObjectLambdaAccessPoint} placeholder with the ARN of the S3 Object Lambda Access Point (eg: arn:aws:s3-object-lambda:us-east-2:111111111111:accesspoint/resize-olap). This is provided in the stack outputs.

```bash
aws s3api get-object --bucket '{S3ObjectLambdaAccessPoint}' --key example1.jpg './images/example1-thumbnail.jpg'
```

```bash
aws s3api get-object --bucket '{S3ObjectLambdaAccessPoint}' --key example2.jpg './images/example2-thumbnail.jpg'
```

NOTE: Upgrade to the latest AWS CLI version if you receive the following error when using the get-object command: `Parameter validation failed: Invalid bucket name: Bucket name must match the regex`

## Documentation

* [Introducing Amazon S3 Object Lambda – Use Your Code to Process Data as It Is Being Retrieved from S3](https://aws.amazon.com/blogs/aws/introducing-amazon-s3-object-lambda-use-your-code-to-process-data-as-it-is-being-retrieved-from-s3/)
* [Transforming objects with S3 Object Lambda](https://docs.aws.amazon.com/AmazonS3/latest/userguide/transforming-objects.html)
* [S3 Object Lambda pricing](https://aws.amazon.com/s3/pricing/)

## Cleanup
 
1. From the AWS Management Console, empty the S3 bucket that contains the example images.
1. Delete the stack
    ```bash
    aws cloudformation delete-stack --stack-name STACK_NAME
    ```
1. Confirm the stack has been deleted
    ```bash
    aws cloudformation list-stacks --query "StackSummaries[?contains(StackName,'STACK_NAME')].StackStatus"
    ```
----
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