AWS EC2 Instance and API Gateway Integration: Troubleshooting JavaScript Errors

Troubleshooting JavaScript Errors

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Question

You have an application that is hosted on an EC2 Instance.

This application is part of a custom domain www.demo.com.

The application has been changed to make calls to the API gateway.

But the browser is not rendering the responses and Javascript errors are being seen in the developer console.

What must be done to ensure that this issue can be resolved?

Answers

Explanations

Click on the arrows to vote for the correct answer

A. B. C. D.

Answer - D.

This is given in the AWS Documentation.

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When your API's resources receive requests from a domain other than the API's own domain, you must enable cross-origin resource sharing (CORS) for selected methods on the resource.

This amounts to having your API respond to the OPTIONS preflight request with at least the following CORS-required response headers:

Access-Control-Allow-Methods.

Access-Control-Allow-Headers.

Access-Control-Allow-Origin.

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Option A is invalid because you should not make the architecture change, since this is not the underlying issue.

Option B is invalid because this is the problem with CORS and not the stage itself.

Option C is invalid because using Cognito user pools would add one more unnecessary layer of authentication which is not part of the question requirement.

For more information on CORS for API gateway, please refer to the below URL-

https://docs.aws.amazon.com/apigateway/latest/developerguide/how-to-cors.html

The issue here is that the application hosted on the EC2 instance is making calls to the API Gateway, but the browser is not rendering the responses and JavaScript errors are being seen in the developer console. This indicates a cross-origin resource sharing (CORS) issue, as the browser is blocking the API Gateway responses due to the security policy in place.

To resolve this issue, we need to enable CORS for the API Gateway. This can be done by configuring the API Gateway to include the necessary CORS headers in its responses. The headers can be set up in the API Gateway's integration response configuration.

Enabling CORS allows the application hosted on the EC2 instance to access the API Gateway, which is hosted on a different domain. This is necessary to allow the browser to render the responses correctly and prevent JavaScript errors from occurring.

Option A, making the application call a Lambda function instead, would not resolve the CORS issue. This option is not relevant to the problem at hand.

Option B, defining a new stage, would also not resolve the CORS issue. This option is related to API Gateway configuration and versioning, but it is not relevant to the problem at hand.

Option C, making use of Cognito user pools, is not relevant to the problem at hand. Cognito user pools are used for user authentication and authorization, but they do not address the CORS issue.

Therefore, the correct answer is option D, enabling CORS for the API Gateway.