Cloud API Gateway doesn't allow with CORS

Question

I have Cloud Gateway API that connects to Cloud Function. It worked great with an API key that I generated, but then when I restricted the key to enable access for my specific domain only - example.com, I started to get CORS errors on the client. ( it worked without domain restriction)

So I enabled CORS in the config file in the Console, the file had no errors, but I still get a CORS error when accessing the API URL from my domain with the key:

https://project-xxxx.uc.gateway.dev/search?key=AIxxxxxxxxx

Config :

swagger: "2.0"
info:
  title: projectapi
  description: "data api"
  version: "1.0.0"
schemes:
  - "https"
host: "project-xxxxxxxx.apigateway.xxxxx-xxxxx.cloud.goog"
x-google-endpoints:
- name: "project-xxxxxxxx.apigateway.xxxxx-xxxxx.cloud.goog"
  allowCors: True  
paths:
  "/search":
    get:
      description: "data"
      operationId: "project"
      x-google-backend:
        address: https://us-central1-projectName.cloudfunctions.net/search
      security:
        - api_key: [key]
      responses:
        200:
          description: "Success."
          schema:
            type: string
        400:
          description: "Invalid"

securityDefinitions:
 api_key:
    type: "apiKey"
    name: "key"
    in: "query" 

My Cloud Function does allow CORS, and works great if called directly with the link here in the address key.

Why this config wont allow CORS for the Gateway ?

Answer 1

Solved ! You must enable the key not only for your domain name, but also for your specific API name from the list, go to APIs & Services => Credentials => API keys => your key => API restrictions => choose your API name from the list !

This allow access to a Function from a specific domain - without using a Balancer.