cypress: XHR requests are cancelled and re-issued if they don't return in 30 seconds

Current behavior:

When an XHR request takes more than 30 seconds to complete, Cypress cancels the request and issues it again. Depending on what the server does with those requests, this can cause all sorts of problems (e.g. creating duplicate things, or directly resulting in failed tests when the server replies with a 5xx error that it wouldn’t have issued if the request hadn’t been sent twice).

Desired behavior:

Cypress should never retry an XHR request on its own, because it cannot know what the effects of a duplicate request could be.

Test code to reproduce

cypress-bug.zip (also contains the video generated by Cypress for the failing test).

I used the code in that zip file to generate the screen recording below. The idea is to set up a web server with an API call that takes 34 seconds to reply, then run a Cypress test that visits the home of the web server (which just issues an XHR call to the API method) and waits for the API response, with a timeout longer than the time it takes for the API to respond. You’ll see on the logs of the webserver that the API method gets called twice, the second one pretty much exactly 30 seconds after the first one.

To work with the code:

• run npm i on both the webserver and tester folders
• run node index.js from the webserver folder
• once it’s running, npm run cypress from the tester folder

You’ll see that the webserver logs one call to /, one to /api, and ~30 seconds later another call to /api. Cypress then reports a failed test.

Versions

The issue happens starting with Cypress 3.8.0 (tested with 3.6.1, 3.7.0, 3.8.0, 4.0.1) Windows 10 Headless tests with Electron

Additional information

I originally discovered this with the Cypress Docker images. In the project where I found it I could even see Nginx reporting that the client (Cypress running tests) had closed the connection, right before receiving the duplicate request.

Screen recording of the code above showing the issue.