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[🐛 Bug]: Can't use DevTools features with Selenium Grid on Docker

See original GitHub issue

What happened?

Not sure if this is strictly a bug, but at least the documentation regarding this issue is missing.

I managed to work with DevTools features in Selenium 4 locally, but when I tried to use it on Selenium Grid, it didn’t work.

In order to investigate it, I installed a local grid with one Chrome node using docker-compose and I got the same error:

OpenQA.Selenium.WebDriverException : Unexpected error creating WebSocket DevTools session.
  ----> System.Net.WebSockets.WebSocketException : Unable to connect to the remote server
  ----> System.Net.Http.HttpRequestException : A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond. (172.18.0.3:4444)
  ----> System.Net.Sockets.SocketException : A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond.

Where 172.18.0.3 is the private IP of chrome-node container.

I guess that the main reason is that I don’t have access to that IP from the host, and that’s probably a docker configuration matter, on which I’m not an expert. But that wasn’t the only problem.

Using the debugger, I was able to track that the driver tries to use this address due to the following capability that is returned from the driver after creation: "se:cdp": "ws://172.18.0.3:4444/session/2c519f679e1060cdc926ca74e63e222f/se/cdp". I then tweaked this value (in the debugger, before trying to create the connection to the DevTools protocol) to use localhost instead of the private IP, and then I got the following error: IOException: The response ended prematurely..

What do I need to do in order to use the DevTools features of Selenium through Selenium Grid (and docker)?

PS: also posted this question on StackOverflow here.

How can we reproduce the issue?

Docker-compose:

# To execute this docker-compose yml file use `docker-compose -f docker-compose-v3.yml up`
# Add the `-d` flag at the end for detached execution
# To stop the execution, hit Ctrl+C, and then `docker-compose -f docker-compose-v3.yml down`
version: "3"
services:
  chrome:
    image: selenium/node-chrome:4.4.0-20220831
    shm_size: 2gb
    depends_on:
      - selenium-hub
    environment:
      - SE_EVENT_BUS_HOST=selenium-hub
      - SE_EVENT_BUS_PUBLISH_PORT=4442
      - SE_EVENT_BUS_SUBSCRIBE_PORT=4443
    ports:
      - "4444:4444"

  selenium-hub:
    image: selenium/hub:4.4.0-20220831
    container_name: selenium-hub
    ports:
      - "4442:4442"
      - "4443:4443"
      - "4445:4444"

(Note: I exposed port 4444 from the node-chrome container and redirected the hub’s 4444 to 4445, so that both will be accessible from the host)

public class MyTestClass
{
        [Test]
        public void ConnectToRemoteDevTools()
        {
            var chromeOptions = new ChromeOptions();
            using var driver = new RemoteWebDriver(new Uri("http://localhost:4445/"), chromeOptions.ToCapabilities(), TimeSpan.FromMinutes(10));

            // This line throws the exception:
            var devTools = driver.GetDevToolsSession(104);
        }
}