Simple AWS SAM Application

Updated Feb 11, 2025 ·

Overview

AWS Serverless Application Model (SAM) is framework for developing and deploying serverless applications in AWS.

All the configuration for SAM is stored in YAML code.
Deploy the services automatically (similar to CloudFormation).
Help to run Lambda, API Gateway and DynamoDB locally.
SAM can used CodeDeploy for quick deployments and pipelines.

For more information, please see AWS SAM.

Pre-requisites

You will need to install the following in your local computer:

If you are using Ubuntu 22.04, you might only be able to install Python 3.10.

Python 3.12

Authenticate Your CLI

To use the AWS SAM CLI, first create an IAM user in the AWS Console and generate access keys for that user. Attach the AdministratorAccess policy to this user temporarily to ensure they have the necessary permissions to run AWS SAM CLI commands.

For more information, see IAM Users and Access Keys.

Create the Base Configuration File

We can create our own base configuration file, but we can also let AWS SAM initialize a base config file.

sam init

It will return the following response. Enter 1 to select quickstart templates for testing and then choose the Hello World example. You can choose the runtime as well as enable tX-Ray tracing and CloudWatch Insights. For lab purposes, we just need the structured logging.

It will create a directory that contains the configuration files.

$ ls -la
total 24
drwxrwxrwx 1 joseeden joseeden  512 Nov  2 16:48 .
drwxrwxrwx 1 joseeden joseeden  512 Nov  2 16:48 ..
-rwxrwxrwx 1 joseeden joseeden 3730 Nov  2 16:48 .gitignore
-rwxrwxrwx 1 joseeden joseeden 8329 Nov  2 16:48 README.md
-rwxrwxrwx 1 joseeden joseeden    0 Nov  2 16:48 __init__.py
drwxrwxrwx 1 joseeden joseeden  512 Nov  2 16:48 events
drwxrwxrwx 1 joseeden joseeden  512 Nov  2 16:48 hello_world
-rwxrwxrwx 1 joseeden joseeden  669 Nov  2 16:48 samconfig.toml
-rwxrwxrwx 1 joseeden joseeden 1965 Nov  2 16:48 template.yaml
drwxrwxrwx 1 joseeden joseeden  512 Nov  2 16:48 tests

The Lambda function code can be found in hello_world/app.py:

import json

# import requests


def lambda_handler(event, context):
    """Sample pure Lambda function

    Parameters
    ----------
    event: dict, required
        API Gateway Lambda Proxy Input Format

        Event doc: https://docs.aws.amazon.com/apigateway/latest/developerguide/set-up-lambda-proxy-integrations.html#api-gateway-simple-proxy-for-lambda-input-format

    context: object, required
        Lambda Context runtime methods and attributes

        Context doc: https://docs.aws.amazon.com/lambda/latest/dg/python-context-object.html

    Returns
    ------
    API Gateway Lambda Proxy Output Format: dict

        Return doc: https://docs.aws.amazon.com/apigateway/latest/developerguide/set-up-lambda-proxy-integrations.html
    """

    # try:
    #     ip = requests.get("http://checkip.amazonaws.com/")
    # except requests.RequestException as e:
    #     # Send some context about this error to Lambda Logs
    #     print(e)

    #     raise e

    return {
        "statusCode": 200,
        "body": json.dumps({
            "message": "hello world",
            # "location": ip.text.replace("\n", "")
        }),
    }
 

Build and Package the Application

After initializing the project, the next step is to build and package the application. Go to the project directory and run:

cd sam-app
sam build
sam deploy 

After it's done, it will print the outputs, including the application URL.

CloudFormation outputs from deployed stack
-------------------------------------------------------------------------------------------------------------   
Outputs                                                                                                         
-------------------------------------------------------------------------------------------------------------   
Key                 HelloWorldFunctionIamRole                                                                   
Description         Implicit IAM Role created for Hello World function                                          
Value               arn:aws:iam::841234567890:role/sam-app-HelloWorldFunctionRole-ojmSC0FUjVZg                  

Key                 HelloWorldApi                                                                               
Description         API Gateway endpoint URL for Prod stage for Hello World function                            
Value               https://6doirma1pc.execute-api.ap-southeast-1.amazonaws.com/Prod/hello/                     

Key                 HelloWorldFunction                                                                          
Description         Hello World Lambda Function ARN                                                             
Value               arn:aws:lambda:ap-southeast-1:841234567890:function:sam-app-HelloWorldFunction-             
Nob9YL9Sg1YW                                                                                                    
-------------------------------------------------------------------------------------------------------------

Open a web browser and enter the URL:

https://6doirma1pc.execute-api.ap-southeast-1.amazonaws.com/Prod/hello/

In the AWS dashboard, we should also see the created Lambda function.

Cleanup

To delete the function:

sam delete

Enter y twice to confirm:

Are you sure you want to delete the stack sam-app in the region ap-southeast-1 ? [y/N]: y
Do you want to delete the template file 0cfc681b8281d439d475f4ca2090e4ac.template in S3? [y/N]: y
- Deleting S3 object with key 472b4bdb4a2b33287061ad1bf41a08ed
- Deleting S3 object with key 0cfc681b8281d439d475f4ca2090e4ac.template
- Deleting Cloudformation stack sam-app

Deleted successfully 

Overview​

Pre-requisites​

Authenticate Your CLI​

Create the Base Configuration File​

Build and Package the Application​

Cleanup​