# Create Resources with AWS SAM

This project contains source code and supporting files for a serverless application that you can deploy with the AWS Serverless Application Model (AWS SAM) command line interface (CLI). This SAM application will create an AWS Lambda function that uses the SQS queue as its event source. Notice in particular the AWS CloudFormation dynamic reference contained in the template.yaml file that retrieves the SQS queue arn stored in SSM Parameter Store.

This project includes the following files and folders:

- `src` - Code for the application's Lambda function.
- `events` - Invocation events that you can use to invoke the function.
- `__tests__` - Unit tests for the application code. 
- `template.yaml` - A template that defines the application's AWS resources.

Resources for this project are defined in the `template.yaml` file in this project. You can update the template to add AWS resources through the same deployment process that updates your application code.

If you prefer to use an integrated development environment (IDE) to build and test your application, you can use the AWS Toolkit.  
The AWS Toolkit is an open-source plugin for popular IDEs that uses the AWS SAM CLI to build and deploy serverless applications on AWS. The AWS Toolkit also adds step-through debugging for Lambda function code. 

To get started, see the following:

* [CLion](https://docs.aws.amazon.com/toolkit-for-jetbrains/latest/userguide/welcome.html)
* [GoLand](https://docs.aws.amazon.com/toolkit-for-jetbrains/latest/userguide/welcome.html)
* [IntelliJ](https://docs.aws.amazon.com/toolkit-for-jetbrains/latest/userguide/welcome.html)
* [WebStorm](https://docs.aws.amazon.com/toolkit-for-jetbrains/latest/userguide/welcome.html)
* [Rider](https://docs.aws.amazon.com/toolkit-for-jetbrains/latest/userguide/welcome.html)
* [PhpStorm](https://docs.aws.amazon.com/toolkit-for-jetbrains/latest/userguide/welcome.html)
* [PyCharm](https://docs.aws.amazon.com/toolkit-for-jetbrains/latest/userguide/welcome.html)
* [RubyMine](https://docs.aws.amazon.com/toolkit-for-jetbrains/latest/userguide/welcome.html)
* [DataGrip](https://docs.aws.amazon.com/toolkit-for-jetbrains/latest/userguide/welcome.html)
* [VS Code](https://docs.aws.amazon.com/toolkit-for-vscode/latest/userguide/welcome.html)
* [Visual Studio](https://docs.aws.amazon.com/toolkit-for-visual-studio/latest/user-guide/welcome.html)

## Deploy the sample application

The AWS SAM CLI is an extension of the AWS CLI that adds functionality for building and testing Lambda applications. It uses Docker to run your functions in an Amazon Linux environment that matches Lambda. It can also emulate your application's build environment and API.

To use the AWS SAM CLI, you need the following tools:

* AWS SAM CLI - [Install the AWS SAM CLI](https://docs.aws.amazon.com/serverless-application-model/latest/developerguide/serverless-sam-cli-install.html).
* Node.js - [Install Node.js 14](https://nodejs.org/en/), including the npm package management tool.
* Docker - [Install Docker community edition](https://hub.docker.com/search/?type=edition&offering=community).

Navigate to the `terraform-sam-integration/sam` directory of this project.

To build and deploy your application for the first time, run the following in your shell:

```bash
sam build
sam deploy --guided
```

The first command will build the source of your application. The second command will package and deploy your application to AWS, with a series of prompts:

* **Stack Name**: The name of the stack to deploy to CloudFormation. This should be unique to your account and region, and a good starting point would be something matching your project name.
* **AWS Region**: The AWS region you want to deploy your app to.
* **Confirm changes before deploy**: If set to yes, any change sets will be shown to you before execution for manual review. If set to no, the AWS SAM CLI will automatically deploy application changes.
* **Allow SAM CLI IAM role creation**: Many AWS SAM templates, including this example, create AWS IAM roles required for the AWS Lambda function(s) included to access AWS services. By default, these are scoped down to minimum required permissions. To deploy an AWS CloudFormation stack which creates or modifies IAM roles, the `CAPABILITY_IAM` value for `capabilities` must be provided. If permission isn't provided through this prompt, to deploy this example you must explicitly pass `--capabilities CAPABILITY_IAM` to the `sam deploy` command.
* **Save arguments to samconfig.toml**: If set to yes, your choices will be saved to a configuration file inside the project, so that in the future you can just re-run `sam deploy` without parameters to deploy changes to your application.

## Send a test message to the queue 

Once your deployment is complete you can send a message to the queue. The Lambda function will process the message. You can view the log results in CloudWatch logs.

```bash
aws sqs send-message --queue-url "<insert queue url here>" --message-body "Red five standing by." --region=us-west-1
```

## Check out SAM sync

SAM has the capability to synchronize your local code with your cloud environment to speed up developer iteration cycles. 

**[Watch this YouTube video](https://www.youtube.com/watch?v=DDhOa4ekn80&ab_channel=ServerlessLand)** for an explanation and demo. 

The video is 22 minutes long, but understanding SAM sync could save you hours of time. 

## Use the AWS SAM CLI to build and test locally

Build your application by using the `sam build` command.

```bash
sam build
```

The AWS SAM CLI installs dependencies that are defined in `package.json`, creates a deployment package, and saves it in the `.aws-sam/build` folder.

Test a single function by invoking it directly with a test event. An event is a JSON document that represents the input that the function receives from the event source. Test events are included in the `events` folder in this project.

Run functions locally and invoke them with the `sam local invoke` command.

```bash
sam local invoke SQSPayloadLogger --event events/event-sqs.json
```

## Add a resource to your application

The application template uses AWS SAM to define application resources. AWS SAM is an extension of AWS CloudFormation with a simpler syntax for configuring common serverless application resources, such as functions, triggers, and APIs. For resources that aren't included in the [AWS SAM specification](https://github.com/awslabs/serverless-application-model/blob/master/versions/2016-10-31.md), you can use the standard [AWS CloudFormation resource types](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-template-resource-type-ref.html).

Update `template.yaml` to add a dead-letter queue to your application. In the **Resources** section, add a resource named **MyQueue** with the type **AWS::SQS::Queue**. Then add a property to the **AWS::Serverless::Function** resource named **DeadLetterQueue** that targets the queue's Amazon Resource Name (ARN), and a policy that grants the function permission to access the queue.

```
Resources:
  MyQueue:
    Type: AWS::SQS::Queue
  SQSPayloadLogger:
    Type: AWS::Serverless::Function
    Properties:
      Handler: src/handlers/sqs-payload-logger.sqsPayloadLoggerHandler
      Runtime: nodejs14.x
      DeadLetterQueue:
        Type: SQS
        TargetArn: !GetAtt MyQueue.Arn
      Policies:
        - SQSSendMessagePolicy:
            QueueName: !GetAtt MyQueue.QueueName
```

The dead-letter queue is a location for Lambda to send events that could not be processed. It's only used if you invoke your function asynchronously, but it's useful here to show how you can modify your application's resources and function configuration.

Deploy the updated application.

```bash
sam deploy
```

Open the [**Applications**](https://console.aws.amazon.com/lambda/home#/applications) page of the Lambda console, and choose your application. When the deployment completes, view the application resources on the **Overview** tab to see the new resource. Then, choose the function to see the updated configuration that specifies the dead-letter queue.

## Fetch, tail, and filter Lambda function logs

To simplify troubleshooting, the AWS SAM CLI has a command called `sam logs`. `sam logs` lets you fetch logs that are generated by your Lambda function from the command line. In addition to printing the logs on the terminal, this command has several nifty features to help you quickly find the bug.

**NOTE:** This command works for all Lambda functions, not just the ones you deploy using AWS SAM.

```bash
sam logs -n SQSPayloadLogger --stack-name sam-app --tail
```

**NOTE:** This uses the logical name of the function within the stack. This is the correct name to use when searching logs inside an AWS Lambda function within a CloudFormation stack, even if the deployed function name varies due to CloudFormation's unique resource name generation.

You can find more information and examples about filtering Lambda function logs in the [AWS SAM CLI documentation](https://docs.aws.amazon.com/serverless-application-model/latest/developerguide/serverless-sam-cli-logging.html).

## Unit tests

Tests are defined in the `__tests__` folder in this project. Use `npm` to install the [Jest test framework](https://jestjs.io/) and run unit tests.

```bash
npm install
npm run test
```

## Cleanup

To delete the sample application and the bucket that you created:

```bash
sam delete
```

or

```bash
aws cloudformation delete-stack --stack-name sam-app
aws s3 rb s3://BUCKET_NAME
```

## Resources

For an introduction to the AWS SAM specification, the AWS SAM CLI, and serverless application concepts, see the [AWS SAM Developer Guide](https://docs.aws.amazon.com/serverless-application-model/latest/developerguide/what-is-sam.html).