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CoreUtilities

This project contains source code and supporting files for a serverless application that you can deploy with the SAM CLI. It includes Powertools for AWS Lambda (Java) for operational best practices, and the following files and folders.

  • HelloWorldFunction/src/main - Code for the application's Lambda function.
  • events - Invocation events that you can use to invoke the function.
  • HelloWorldFunction/src/test - 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 and an API Gateway API. 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.

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 plug-in for popular IDEs that uses the SAM CLI to build and deploy serverless applications on AWS. The AWS Toolkit also adds a simplified step-through debugging experience for Lambda function code. See the following links to get started.

Deploy the sample application

This sample is based on Serverless Application Model (SAM). To deploy it, check out the instructions for getting started with SAM in the examples directory

Use the SAM CLI to build and test locally

Build your application with the sam build command.

Coreutilities$ sam build

The SAM CLI installs dependencies defined in HelloWorldFunction/pom.xml, 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.

Coreutilities$ sam local invoke HelloWorldFunction --event events/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.

Coreutilities$ sam local start-api
Coreutilities$ curl http://localhost:3000/

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

Add a resource to your application

The application template uses AWS Serverless Application Model (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 not included in the SAM specification, you can use standard AWS CloudFormation resource types.

Fetch, tail, and filter Lambda function logs

To simplify troubleshooting, SAM CLI has a command called sam logs. sam logs lets you fetch logs generated by your deployed 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 AWS Lambda functions; not just the ones you deploy using SAM.

Coreutilities$ sam logs -n HelloWorldFunction --stack-name <Name-of-your-deployed-stack> --tail

You can find more information and examples about filtering Lambda function logs in the SAM CLI Documentation.

Unit tests

Tests are defined in the HelloWorldFunction/src/test folder in this project.

Coreutilities$ cd HelloWorldFunction
HelloWorldFunction$ mvn test

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 <Name-of-your-deployed-stack>

Appendix

Powertools

Tracing

Tracing utility provides functionality to reduce the overhead of performing common tracing tasks. It traces the execution of this sample code including the response and exceptions as tracing metadata - You can visualize them in AWS X-Ray.

Logger

Logging utility creates an opinionated application Logger with structured logging as the output, dynamically samples a percentage (samplingRate) of your logs in DEBUG mode for concurrent invocations, log incoming events as your function is invoked, and injects key information from Lambda context object into your Logger - You can visualize them in Amazon CloudWatch Logs.

Metrics

Metrics utility captures cold start metric of your Lambda invocation, and could add additional metrics to help you understand your application KPIs - You can visualize them in Amazon CloudWatch.

Resources

See the AWS SAM developer guide for an introduction to SAM specification, the SAM CLI, and serverless application concepts.

Check the Powertools for AWS Lambda (Java) for more information on how to use and configure such tools

Next, you can use AWS Serverless Application Repository to deploy ready to use Apps that go beyond hello world samples and learn how authors developed their applications: AWS Serverless Application Repository main page