API Gateway to Lambda Functions

Introduction

• Create a RESTful API Gateway endpoint to invoke a Lambda function.
• Return JSON to the client.

Steps

Create Lambda Function

1. Function Name: TransactionHandler.
2. Input: Event object with query string parameters.
3. Resource Setup: Transactions resource with a GET API forwarding requests to the Lambda function.
4. Response: Hard-coded response (in applications, process query parameters and interact with other AWS services).
5. Testing: Invoke endpoint from the browser and observe response.

Console Actions

Lambda Setup

1. Navigate to Lambda Section.
2. Create Function: From scratch, named TransactionProcessor.
3. Runtime: Python 3.6.
4. Permissions: Basic CloudWatch permissions (included in new role with basic Lambda permissions).
5. Click Create.

Coding in Sublime Text

1. Steps in Function
   • Parse query string parameters (transactionID, transactionType, amount).
   • Print parameters for verification.
   • Construct response body as a JSON object.
   • Include echo values received and a custom message.
   • Build HTTP response object with status code, headers, and body.
   • Return the response.
2. Code Move: Copy from Sublime Text to Lambda console and save.

API Gateway Setup

1. Navigate to API Gateway Section.
2. Create API: Select New API.
   • Name: TransactionAPIs.
   • Endpoint Type: Default.
3. Create Resource: Named transactions.
4. Create Method: GET method.
   • Backend: Lambda function.
   • Lambda Proxy Integration: True.
   • Lambda Function: TransactionProcessor.
   • Save and grant API Gateway permission to invoke Lambda.

Deploy API

1. Navigate to Deploy API.
2. Create Stage: Name it test.
3. Deploy: Test environment deployed.
   • Endpoint URL: Copy the URL.
4. Send Request from browser with query string parameters.

Testing and Verification

• Example Call: /transactions?transactionID=5&type=purchase&amount=500.
  • Expected JSON Response: { transactionID: 5, type: 'purchase', amount: 500, message: 'Hello from LambdaLand' }.

CloudWatch Logs

• Navigate to CloudWatch.
• Logs: Verify logs for transaction ID, type, and amount.

Conclusion

• Quick wrap-up of creating and testing API Gateway with Lambda integration.
• Encourage viewers to share use cases.
• Reminder to like and subscribe.