API Gateway calling Cloud Function via Load Balancer causes CORS errors in web application. How do I modify the OpenAPI config to support CORS and add custom authentication endpoint?
Based on my experience, I addressed the CORS issue by revising the OpenAPI configuration to include an OPTIONS method at the path level for each endpoint. I configured the responses to automatically include the necessary headers, such as Access-Control-Allow-Origin, Access-Control-Allow-Methods, and Access-Control-Allow-Headers. For custom authentication, I integrated a separate endpoint that validates tokens before the main function receives the request, using API Gateway’s security definitions. Adjusting these settings and testing in different environments resolved the errors and streamlined the authentication flow.