DevToolsActivePort file doesn't exist error message. Selenium in Python running on MacOS

Question

I've got a project that uses the Chrome webdriver with Selenium and came across an intermittent DevToolsActivePort issue that prevented the webdriver from starting. As usual, it was a simple problem, but it took a while to determine the cause.

TLDR: Try manually opening and closing Chrome. Check your script's shutdown process.

Software Versions:

• macOS: 13.0.1
• Python: 3.9.6
• Selenium: 4.8.2
• Chrome: 113.0.5672.92

Error message:

Message: unknown error: Chrome failed to start: exited normally.
  (unknown error: DevToolsActivePort file doesn't exist)
  (The process started from chrome location /Applications/Google Chrome.app/Contents/MacOS/Google Chrome is no longer running, so ChromeDriver is assuming that Chrome has crashed.)

Here is a snippet of the driver initialization:

from selenium import webdriver
from selenium.webdriver.chrome.service import Service
from webdriver_manager.chrome import ChromeDriverManager

prefs = {
  "download.default_directory": Download_dir,
  'download.prompt_for_download': False,
  'directory_upgrade': True,
  'safebrowsing.enabled': True,
  'profile.default_content_setting_values.automatic_downloads': 1,
  'profile.default_content_settings.popups': 0,
}

options.add_argument("--headless=new")
options.add_argument("--window-size=1920,1080")
options.add_argument("--disable-extensions")
options.add_argument("--user-data-dir=/Users/<username>/Library/Application Support/Google/Chrome/")
options.add_argument('--profile-directory=Profile 3') # Profile Folder Name
options.binary_location = '/Applications/Google Chrome.app/Contents/MacOS/Google Chrome'
options.add_experimental_option("prefs", prefs)

driver = webdriver.Chrome(service=Service(ChromeDriverManager().install()), options=options)

I saw a lot of posts suggesting to add some options to the driver such as --no-sandbox, --disable-dev-shm-usage which both remove security layers, not ideal, and also did not resolve the issue in my case. I also saw a suggestion to add the --remote-debugging-port=<example port> option to manually choose the port. This is probably the cause of the issue, but I could not find the correct port to use.

I ended up solving the issue by simply opening and quitting Chrome before starting the script. I believe the error was caused by the script not properly closing the Chrome instance which may have caused the debugging port mismatch. By opening and closing Chrome manually, I could ensure a proper shutdown, and the selenium fired right up.

I have now added driver.close() / driver.quit() to the keyboard interrupt block and it seems to have resolved the issue.

Hope this helps the other noobs out there.

Tried:

Initializing the Chrome webdriver in Selenium.

Expected:

Selenium initializes Chrome webdriver.

Results:

Occasionally would fail unknown error: DevToolsActivePort file doesn't exist error.

Solution:

1. Stop the script.
2. Open Chrome.
3. Close Chrome.
4. Start the script.
5. Fix the shutdown procedure.
6. Profit?

Answer 1

If you run your tests on a server, it might help to set the DISPLAY variable to something (any nonempty value?). Even if Chrome runs in --headless mode.

I got these crashes while connecting to a Linux server (which I wanted to run my PHP/Codeception tests on) with ssh <servername> and then both Chrome and Chromium failed to start (to run tests in headless mode), resulting in
unknown error: DevToolsActivePort file doesn't exist.

Connecting with ssh -Y <servername> helped to get rid of the errors. My $DISPLAY variable on my ssh terminal was set to e.g. localhost:11.1 and that was sufficient.
A nonexisting DISPLAY variable led to errors.

(I haven't investigated this further).
(I just realized you run tests on a Mac, so my advice might not apply, but perhaps it helps someone else)