[FIXED] WebDriverException: unknown error: DevToolsActivePort file doesn't exist while trying to initiate Chrome browser (1)

Issue

I've upgraded Ubuntu to 20.04. It seems that Chrome isn't available as APT package but via snap. After the upgrade I'm getting the error while trying to instantiate Chrome browser:

>>> from selenium.webdriver import Chrome
>>> from selenium.webdriver.chrome.options import Options
>>> o = Options()
>>> o.headless = True
>>> o.add_argument('--disable-dev-shm-usage')
>>> o.add_argument('--no-sandbox')
>>> Chrome(options=o)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/var/www/order/lib/python3.8/site-packages/selenium/webdriver/chrome/webdriver.py", line 76, in __init__
    RemoteWebDriver.__init__(
  File "/var/www/order/lib/python3.8/site-packages/selenium/webdriver/remote/webdriver.py", line 157, in __init__
    self.start_session(capabilities, browser_profile)
  File "/var/www/order/lib/python3.8/site-packages/selenium/webdriver/remote/webdriver.py", line 252, in start_session
    response = self.execute(Command.NEW_SESSION, parameters)
  File "/var/www/order/lib/python3.8/site-packages/selenium/webdriver/remote/webdriver.py", line 321, in execute
    self.error_handler.check_response(response)
  File "/var/www/order/lib/python3.8/site-packages/selenium/webdriver/remote/errorhandler.py", line 242, in check_response
    raise exception_class(message, screen, stacktrace)
selenium.common.exceptions.WebDriverException: Message: unknown error: DevToolsActivePort file doesn't exist

chromedriver version is 87.0.4280.20 chromium-browser version is Chromium 87.0.4280.66 snap

I read this discussion. The case is however isn't same. I run python as a regular user. However I've disabled dev-shm-usage and sandbox. But still it doesn't work. It worked before I've upgraded to Ubuntu 20.04. So I assume it has something to do with snap version of Chrome.

I have found out following configuration works:

Start first Chrome chromium-browser --headless --remote-debugging-port=9222 and then:

>>> from selenium.webdriver import Chrome
>>> from selenium.webdriver.chrome.options import Options
>>> o = Options()
>>> o.add_experimental_option('debuggerAddress', 'localhost:9222')
>>> b = Chrome(options=o)
>>> b.get('https://google.com')
>>> b.title
'Google'
>>>

So it seems the problem is with starting the browser.

Opened a bug report

Solution

Good explanation was provided by ChromeDriver development team in a response to the ticket I've submitted:

ChromeDriver uses the /tmp directory to communicate with Chromium, but Snap remaps /tmp directory to a different location (specifically, to /tmp/snap.chomium/tmp). This causes errors because ChromeDriver can't find files created by Chromium. ChromeDriver is designed and tested with Google Chrome, and it may have compatibility issues with third-party distributions.

There are a couple of workarounds:

1. Tell ChromeDriver to use a location in your home directory, instead of /tmp. For example, if your home directory is /home/me, you can add the following line of code to your script:
   o.add_argument('--user-data-dir=/home/me/foo')

2. Explicitly select a port for ChromeDriver to communiate with Chromium. You need to carefully select a port (e.g., 9222) that isn't already in use, and then add the following line to your script:
   o.add_argument('--remote-debugging-port=9222')

and

Another (probably better) workaround is to use the ChromeDriver installed by Snap, which is at /snap/bin/chromium.chromedriver. E.g., driver = Chrome('/snap/bin/chromium.chromedriver', options=o)

Since this version of ChromeDriver runs inside Snap, its /tmp directory is redirected in the same way as Chromium

Answered By - Ralfeus