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Zorluk: OrtaTroubleshooting API Gateway Errors and CORS

A `502 Bad Gateway` error occurs when a locally running Electron desktop application sends an HTTP `POST` request to an Amazon API Gateway REST API. The developer also notices a CORS failure message in the application logs: 'Origin http://localhost:8080 is not allowed by Access-Control-Allow-Origin'. The API Gateway endpoint uses a Lambda proxy integration. The backend Lambda function's logs in Amazon CloudWatch show that the function completes successfully and returns the following structure:

{
"status": 200,
"body": {
"message": "Data processed successfully",
"itemId": "12345"
}
}

Which changes must the developer make to resolve both the `502 Bad Gateway` error and the CORS block? (Select TWO.)

  1. Modify the Lambda function's output to use the key 'statusCode' instead of 'status', and convert the JSON object in 'body' into a stringified JSON format.Cevap
  2. Add a 'headers' object containing the 'Access-Control-Allow-Origin' key set to 'http://localhost:8080' inside the Lambda function's returned JSON payload.Cevap
  3. C
    Configure the API Gateway Integration Response for the POST method to inject the 'Access-Control-Allow-Origin' header.
  4. D
    Apply a CORS policy to the Amazon S3 bucket that hosts the static assets of the desktop application.
  5. E
    Change the integration type from Lambda Proxy to HTTP Proxy and define a URL path parameter mapping for the backend.

Cevap

To resolve the issues, the developer must modify the Lambda function to return a correctly formatted JSON response with a 'statusCode' key and a stringified JSON 'body' to resolve the 502 Bad Gateway error. The developer must also add the 'Access-Control-Allow-Origin' header to the 'headers' map in the Lambda function's response to resolve the CORS block.
To fix the 502 Bad Gateway error under a Lambda proxy integration, the Lambda function's output must contain the 'statusCode' key (rather than 'status') and the 'body' must be stringified. To resolve the CORS failure, the response payload from the Lambda function must explicitly contain the CORS headers, such as 'Access-Control-Allow-Origin', in the 'headers' object.

Adım Adım Çözüm

1
Correct the response key.
Change the key 'status' to 'statusCode' in the Lambda function's return payload.
API Gateway's parser requires the exact key name 'statusCode' to interpret the HTTP response status code in a Lambda proxy integration.
2
Stringify the body content.
Apply JSON.stringify() to the 'body' object.
Under Lambda proxy integration, API Gateway expects the 'body' property to be a raw text string, not a nested JSON object.
3
Add the CORS header to the Lambda response.
Insert 'headers': { 'Access-Control-Allow-Origin': 'http://localhost:8080' } into the Lambda return object.
Since Lambda proxy bypasses API Gateway's integration responses, the backend function must return all HTTP headers required by the client browser.

Anahtar Kavram

Lambda Proxy Integration Response Format and CORS Configuration
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Konular

Troubleshooting API Gateway Errors and CORS

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