Testing and deploying your APIs

Developing applications on AWS

Ricardo Sueiras

Principal Technologist

Infrastructure-as-Code for developers

 

• Cloud native apps deploy using Infrastructure-as-Code (IaC).
• Define cloud resources in configuration files.
• Avoids manual setup in the AWS Management Console (clickops).

AWS CloudFormation

 

• The foundational IaC service in AWS.
• Define AWS resources with YAML or JSON templates.

AWS Cloud Development Kit (CDK)

 

• CDK defines IaC using code.
• Write in Python, TypeScript, or Java instead of YAML or JSON.
• Apps synthesize into CloudFormation templates at deploy time.

AWS Serverless Application Model (SAM)

• Extends CloudFormation.
• Simplified syntax for serverless resources and APIs.
• Acts as a transformation layer.
• Translates SAM syntax into full CloudFormation templates.

 

SAM features

• Auto-generates least-privilege IAM roles, with room to fine-tune.
• Define your deployment pipeline as configuration.
• Package and deploy with sam build and sam deploy.
• Catch template errors early with sam validate.
• Emulate Lambda locally with sam local start-lambda.
  • Provides a persistent local endpoint

 

Testing with SAM

• Build, invoke, and test serverless apps locally before deploy.
• Test Lambda functions and API Gateway integrations.
• Invoke a function locally with sam local invoke.
  • One-shot invocation
• Emulate API Gateway with sam local start-api.

 

Unit tests

 

• Use SAM with unit tests to validate Lambda behavior.
• Local testing speeds up development cycles.
• Pair with frameworks like pytest, JUnit, or Jest.

Testing workflow

 

• Generate test events with sam local generate-event.
• It outputs JSON event files.
• Invoke locally with sam local invoke FunctionName -e event.json.
• Add framework assertions to verify the response before deploy.

Mocking AWS services

 

• Combine local testing with mocking libraries like moto.
• Interact with simulated AWS services, no real calls.
• Improves test speed.
• Reduces testing costs.
• Validates error scenarios like throttling or failures.

Continuous integration and continuous deployment (CI/CD)

• SAM apps are commonly deployed via CI/CD pipelines.
• Automate building, testing, packaging, and deploying.
• AWS CodeCommit stores code and SAM templates.
• AWS CodeBuild runs tests and sam build.
• AWS CodePipeline orchestrates the workflow.

 

CI/CD workflow

• Commit source code and SAM template to a repo.
• Run automated tests and validation.
• Package the app with sam build.
• Deploy resources with sam deploy.
• Monitor after deployment with CloudWatch.

 

Troubleshooting deployments

 

• Troubleshooting is a key operational skill.
• Common deployment failures:
• IAM permission issues.
• Invalid SAM or CloudFormation templates.
• Failed Lambda packaging or missing dependencies.
• Incorrect API Gateway configurations.

Troubleshooting deployments

 

• SAM deployments run on CloudFormation under the hood.
• Provides stack events and automatic rollback.
• Helps identify deployment failures.
• Rolls back to restore the previous environment state.

Troubleshooting deployments

 

• Troubleshoot issues using:
• CloudWatch Logs.
• API Gateway execution logs.
• Lambda logs.
• CloudWatch metrics.

Let's practice!

Developing applications on AWS