Performance issues with connection::request() with HTTP 500 status, delays up to 16 seconds

Hi,

I recently faced an issue while doing requests of the following way:

 const requestOptions: HttpRequest = {
      method: 'GET',
      url: `/services/apexrest/website/some-apex-endpoint/${data-id}`,
      headers: {
        'content-type': 'application/json',
      }
    };

   // ...... some code
 const response = await conn.request(requestOptions);

If some-apex-endpoint returns a HTTP 500, the request() call can take up to 16 seconds to return. Adding the option { responseType: 'text' }has had no effect on reducing the execution time.

Replacing the code with a regular Javascript fetch() has reduced the execution back to a more sensible 200 ms average execution time.

Start by reproducing the delay through the conn.request() entry point with an HTTP 500 response, then compare it with the reported fetch() behavior. Inspect the request implementation and determine what causes the excess wait; done means HTTP 500 responses return without the reported delay. No file or test is named in the issue.