zelfick / sam-dynamodb-local

Example app for run SAM with DynamoDB locally

sam-dynamoDB-local

This project contains source code and supporting files for a serverless application that you can deploy with the SAM CLI. It includes the following files and folders.

• hello-world - Code for the application's Lambda function.
• events - Invocation events that you can use to invoke the function.
• hello-world/tests - Unit tests for the application code.
• template.yaml - A template that defines the application's AWS resources.

The application uses several AWS resources, including Lambda functions, API Gateway and DynamoDB. These resources 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.

Tools required

The Serverless Application Model Command Line Interface (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 SAM CLI, you need the following tools.

• SAM CLI - Install the SAM CLI
• Node.js - Install Node.js 12, including the NPM package management tool.
• Docker - Install Docker community edition

Run DynamoDB locally

In the root path of the project create a service for DynamoDB

sam-dynamoDB-local$ docker-compose up -d

Create the table

sam-dynamoDB-local$ bash dynamodb-create-table.sh 

Check if the table has Items

sam-dynamoDB-local$ bash dynamodb-scan-table.sh 

Use the SAM CLI to build and test locally

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

sam-dynamoDB-local$ sam local invoke HelloWorldFunction

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 and pass a json as a parameter.

sam-dynamoDB-local$ sam local invoke PostUser --event event.json

The SAM CLI can also emulate your application's API. Use the sam local start-api to run the API locally on port 3000.

sam-dynamoDB-local$ sam local start-api --docker-network sam-backend
sam-dynamoDB-local$ curl http://localhost:3000/hello

The SAM CLI reads the application template to determine the API's routes and the functions that they invoke. The Events property on each function's definition includes the route and method for each path.

      Events:
        HelloWorld:
          Type: Api
          Properties:
            Path: /hello
            Method: get

Unit tests

Tests are defined in the hello-world/tests folder in this project. Use NPM to install the Mocha test framework and run unit tests.

sam-app-example$ cd hello-world
hello-world$ npm install
hello-world$ npm run test

Build And Deploy

Important

If you want to deploy you need to check that you have the correct environment variables in each lambda funtion and in template.yaml

Create a sam.yml with the following command

sam package --template-file template.yaml --output-template-file sam.yml --s3-bucket "your S3 bucket name"

Deploy to your aws account

sam deploy --template-file sam.yml --stack-name example-sam --capabilities CAPABILITY_IAM

• 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 modified 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.

Cleanup

To delete the sample application that you created, use the AWS CLI. Assuming you used your project name for the stack name, you can run the following:

aws cloudformation delete-stack --stack-name example-sam