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Zorluk: ZorAWS Serverless Application Model (SAM)

A developer is deploying a serverless application using AWS SAM. The application features a Lambda function triggered by an API Gateway HTTP API. After using the AWS SAM CLI to package and deploy the application, the developer observes two issues:
1. The CloudFormation stack deployment fails with an error indicating that the Lambda service is unauthorized to assume the execution role associated with the function.
2. After manual role adjustment, a test request to the API Gateway endpoint fails with a 502 Bad Gateway error, even though the Lambda function executes successfully without code exceptions.

Which TWO actions should the developer take to resolve these issues?

  1. Modify the trust policy of the IAM execution role to allow the lambda.amazonaws.com service principal to perform the sts:AssumeRole action.Cevap
  2. Ensure the Lambda function returns a structured JSON payload containing the statusCode and body keys to match the API Gateway Lambda proxy integration requirements.Cevap
  3. C
    Add the Transform: AWS::Serverless-2016-10-31 declaration inside the IAM execution role's trust policy statements.
  4. D
    Increase the function's Timeout parameter in the Globals section of the template.yaml file to 900 seconds.
  5. E
    Replace the API Gateway event source definition with an AWS Systems Manager Parameter Store dynamic reference in the template.

Cevap

To resolve the issues, the developer must modify the trust policy of the IAM execution role to allow the lambda.amazonaws.com service principal to assume the role, and ensure the Lambda function returns a structured JSON payload containing the statusCode and body keys to match API Gateway Lambda proxy integration requirements.
The correct configurations directly address the two distinct issues. First, the IAM execution role's trust policy must explicitly permit the 'lambda.amazonaws.com' service principal to assume the role via 'sts:AssumeRole'. Second, when using Lambda proxy integration with API Gateway, the Lambda function must return a JSON response containing 'statusCode' and a stringified 'body' for API Gateway to parse the integration response successfully without returning a 502 Bad Gateway error.

Adım Adım Çözüm

1
Analyze the CloudFormation error regarding role authorization.
Identify that the IAM execution role lacks a trust relationship (assume role policy) allowing the Lambda service to assume it.
Without a valid trust policy trusting lambda.amazonaws.com, the Lambda service cannot assume the role to run the code.
2
Analyze the API Gateway 502 Bad Gateway error.
Identify that the Lambda function, under Lambda proxy integration, must return a specific schema containing 'statusCode' and 'body'.
API Gateway requires this structured response to construct the HTTP response; returning arbitrary JSON structures causes a 502 error.
3
Formulate correct configuration adjustments.
Update the execution role's trust policy and modify the function code to return the required JSON response structure.
This fixes both the deployment-time trust issue and the execution-time integration format issue.

Anahtar Kavram

AWS SAM resources rely on correctly configured IAM service trust policies for function execution, and API Gateway Lambda proxy integrations demand a strict return payload contract from the backend Lambda function.
Tahmini Süre:2m 30s
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AWS Serverless Application Model (SAM)

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