# S3 to Lambda

This CDK stack deploys a Lambda function, a S3 bucket, and the minimum IAM resources required to run the application.

When items are written in the S3 bucket, the changes are sent to a stream. This pattern configures a Lambda function to poll this stream, and log some information to CloudWatch. The function is invoked with a payload containing the information of the event.

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
* [Node and NPM](https://nodejs.org/en/download/) installed
* [Git Installed](https://git-scm.com/book/en/v2/Getting-Started-Installing-Git)
* [AWS Cloud Development Kit](https://docs.aws.amazon.com/cdk/latest/guide/getting_started.html#getting_started_install) (AWS CDK) installed

## Deployment Instructions

1. Create a new directory, navigate to that directory in a terminal and clone the GitHub repository:
    ```sh
    git clone https://github.com/aws-samples/serverless-patterns
    ```
1. Change directory to the pattern directory:
    ```sh
    cd s3-lambda-cdk/src
    ```
1. From the command line, use npm to install dependencies:
    ```sh
    npm install
    ```
1. Finally, use AWS CDK to deploy the AWS resources for the pattern as specified in the `lib/s3-to-lambda-cdk-stack.ts` file:
    ```sh
    cdk deploy
    ```

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

## Testing

1. Run the following S3 CLI command to upload a text file to the S3 bucket. Replace `{SourceBucketName}` with the name of the stack that was created. This is provided in the stack outputs in your terminal following `cdk deploy`.

```bash
aws s3 cp './events/test.txt'  s3://{SourceBucketName}
```

2. Go to the [Cloudwatch Log Groups](https://console.aws.amazon.com/cloudwatch/home?#logsV2:log-groups) page and search for the name of the created Lambda function. The CDK deployment process outputs will print the value for **S3ToLambdaCdkStack.LambdaFunctionArn**. If you are using the default one, the function name will be something like `S3ToLambdaCdkStack-readStream-*`, and the log group will be `/aws/lambda/S3ToLambdaCdkStack-readStream-*`

3. If you are able to see the logs with the Event name and request, it worked!

![Cloudwatch](images/cloudwatch-logs.png)


## Cleanup
 
1. Delete the stack
    ```bash
    cdk destroy
    ```
1. Confirm the stack has been deleted
    ```bash
    aws cloudformation list-stacks --query "StackSummaries[?contains(StackName,'STACK_NAME')].StackStatus"
    ```
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