# Integration of Amazon API Gateway REST API with Amazon Lambda and Amazon SNS

The SAM template deploys a API Gateway REST API with Lambda function integration, an SNS topic and the IAM permissions required to run the application. Whenever the REST API is invoked, the Lambda function publishes a message to the SNS topic. The AWS SAM template deploys the resources and the IAM permissions required to run the application.

Learn more about this pattern at Serverless Land Patterns: https://serverlessland.com/patterns/apigw-lambda-sns/.

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
    ``` 
    
2. Change directory to the pattern directory:
    ``` 
    cd apigw-lambda-sns
    ``` 
3. From the command line, use AWS SAM to deploy the AWS resources for the pattern as specified in the template.yaml file:
    ``` 
    sam deploy --guided
    ``` 
4. 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.
    
5. Note the outputs from the SAM deployment process. These contain the resource names and/or ARNs which are used for testing.
    

## Testing

The stack will output the *api endpoint*. You can use Postman or curl to send a GET request to the API Gateway endpoint.

```
curl --location --request GET 'https://<api_id>.execute-api.<region>.amazonaws.com/s1'
```
In order to receive a notification, please make sure to configure subscription in the SNS topic.


## Cleanup


1. Delete the stack 
    ```
    aws cloudformation delete-stack —stack-name STACK_NAME
    ```
2. Confirm the stack has been deleted 
    ```
    aws cloudformation list-stacks —query "StackSummaries[?contains(StackName,'STACK_NAME')].StackStatus"
    ```

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