InvalidArgumentException: Message: invalid argument: user data directory is already in use error using –user-data-dir to start Chrome using Selenium

This error message…

selenium.common.exceptions.InvalidArgumentException: Message: invalid argument: user data directory is already in use, please specify a unique value for --user-data-dir argument, or don't use --user-data-dir

…implies that the ChromeDriver was unable to initiate the new Chrome Browser session using the specified user data directory as it was already in use.

This error can be reproduced as follows:

• Code Block:

  from selenium import webdriver
  import getpass
  
  options = webdriver.ChromeOptions() 
  options.add_argument("start-maximized")
  options.add_argument(r"--user-data-dir=C:\Users\{}\AppData\Local\Google\Chrome\User Data".format(getpass.getuser()))
  driver = webdriver.Chrome(options=options, executable_path=r'C:\WebDrivers\chromedriver.exe')
  driver.get("https://www.google.com/")
  

• Complete relevant traceback:

  [12148:21412:0204/035557.731:ERROR:cache_util_win.cc(21)] Unable to move the cache: Access is denied. (0x5)
  [12148:21412:0204/035557.731:ERROR:cache_util.cc(141)] Unable to move cache folder C:\Users\Soma Bhattacharjee\AppData\Local\Google\Chrome\User Data\ShaderCache\GPUCache to C:\Users\Soma Bhattacharjee\AppData\Local\Google\Chrome\User Data\ShaderCache\old_GPUCache_000
  [12148:21412:0204/035557.731:ERROR:disk_cache.cc(178)] Unable to create cache
  [12148:21412:0204/035557.731:ERROR:shader_disk_cache.cc(605)] Shader Cache Creation failed: -2
  Opening in existing browser session.
  Traceback (most recent call last):
    File "C:\Users\Soma Bhattacharjee\Desktop\Debanjan\PyPrograms\yandex_ru.py", line 18, in <module>
      driver = webdriver.Chrome(options=options, executable_path=r'C:\WebDrivers\chromedriver.exe')
    File "C:\Python\lib\site-packages\selenium\webdriver\chrome\webdriver.py", line 81, in __init__
      desired_capabilities=desired_capabilities)
    File "C:\Python\lib\site-packages\selenium\webdriver\remote\webdriver.py", line 157, in __init__
      self.start_session(capabilities, browser_profile)
    File "C:\Python\lib\site-packages\selenium\webdriver\remote\webdriver.py", line 252, in start_session
      response = self.execute(Command.NEW_SESSION, parameters)
    File "C:\Python\lib\site-packages\selenium\webdriver\remote\webdriver.py", line 321, in execute
      self.error_handler.check_response(response)
    File "C:\Python\lib\site-packages\selenium\webdriver\remote\errorhandler.py", line 242, in check_response
      raise exception_class(message, screen, stacktrace)
  selenium.common.exceptions.InvalidArgumentException: Message: invalid argument: user data directory is already in use, please specify a unique value for --user-data-dir argument, or don't use --user-data-dir
  

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Analysis

The error stack trace clearly complains of Access is denied as the program was unable to move the cache folder ..\ShaderCache\GPUCache to ..\ShaderCache\old_GPUCache_000. hence the creation of cache failed and subsequently creation of Shader Cache Creation failed. Though these issues raises the InvalidArgumentException but forcefully able to open a new window within the existing Chrome Browser Session.

Though the error is thrown, still the new Chrome window gets initiated but remains attached with the already opened Chrome session but the new window can’t be controlled by the WebDriver instance. Hence you see data:, in the url bar.

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Solution

You need to take care of a couple of things:

• If you are using the Default Chrome Profile to access webpages for your other work on the same Test Machine, you shouldn’t set user-data-dir as the User Data as it remains locked by the other Chrome process you have initiated manually.
  • In the above scenario you need to create and use another Chrome Profile and you can find a detailed discussion in How to open a Chrome Profile through Python
• If you are executing your tests in a isolated test system, you can set user-data-dir as ..\User Data\Default to access the Default Chrome Profile.
  • In the above scenario you need to create and use another Chrome Profile and you can find a detailed discussion in How to use Chrome Profile in Selenium Webdriver Python 3
• However as per best practices you must always create a new Chrome Profile to execute your tests as the Default Chrome Profile may contain Extensions, Bookmarks, Browsing History, etc, and may not load properly.
  • You can find a detailed discussion in How to open a Chrome Profile through –user-data-dir argument of Selenium