python - How to fix "WebDriverException: Message: connection refused"?

Question

I am using a very complex setup to test various non-public webpages. I use jenkins to run the python-selenium tests within a dockerimage. That way, I am completly independent of the jenkins environment and can create my own environment. In this environment I have the following software installed:

• Firefox: 57.0.1
• geckodriver: 0.18.0
• nosetests: 1.3.7
• selenium: 3.8.0

The selenium tests create the WebDriver the following way:

profile = webdriver.FirefoxProfile()
profile.set_preference("browser.download.dir", self.downloadpath)
profile.set_preference("browser.download.folderList", 2)
profile.set_preference("browser.download.useDownloadDir", True)
profile.set_preference("browser.download.manager.showWhenStarting", False)
profile.set_preference("pdfjs.disabled", True)
profile.set_preference("browser.helperApps.neverAsk.saveToDisk",
"application/force-download, image/png, text/html, text/plain, "
"image/tiff, text/csv, application/zip, application/octet-stream")
profile.set_preference("browser.download.manager.alertOnEXEOpen", False)
profile.set_preference("browser.download.manager.focusWhenStarting", False)
profile.set_preference("browser.helperApps.alwaysAsk.force", False)
profile.set_preference("browser.download.manager.alertOnEXEOpen", False)
profile.set_preference("browser.download.manager.closeWhenDone", True)
profile.set_preference("browser.download.manager.showAlertOnComplete", False)
profile.set_preference("browser.download.manager.useWindow", False)
profile.set_preference("services.sync.prefs.sync.browser.download.manager.showWhenStarting",
False)
self.driver = webdriver.Firefox(profile, log_path = logfile)

where logfile and self.downloadpath are two valid paths in the docker setup.

The whole test suite consists of 6 independant test cases, each with the same setup as above. They normally run fine and complete without problems.

But without any change to the tests or the general setup, a test sometimes fails with the following error message:

  File "/root/tests/bsp_usecase_tests/tools/basicsuite.py", line 210, in set_driver_firefox
    self.driver = webdriver.Firefox(profile, log_path = logfile)
  File "/usr/local/lib/python2.7/dist-packages/selenium/webdriver/firefox/webdriver.py", line 158, in __init__
    keep_alive=True)
  File "/usr/local/lib/python2.7/dist-packages/selenium/webdriver/remote/webdriver.py", line 154, in __init__
    self.start_session(desired_capabilities, browser_profile)
  File "/usr/local/lib/python2.7/dist-packages/selenium/webdriver/remote/webdriver.py", line 243, in start_session
    response = self.execute(Command.NEW_SESSION, parameters)
  File "/usr/local/lib/python2.7/dist-packages/selenium/webdriver/remote/webdriver.py", line 311, in execute
    self.error_handler.check_response(response)
  File "/usr/local/lib/python2.7/dist-packages/selenium/webdriver/remote/errorhandler.py", line 237, in check_response
    raise exception_class(message, screen, stacktrace)
WebDriverException: Message: connection refused

I have two questions:

1. What connection is refused here? What is the meaning of the error message
2. How can I possibly fix this error?

Addendum:

• When I used a time.sleep(10) just before the webdriver.Firefox line, the error did not show up anymore. Shoud I put that line in a while-try-except loop?

Answer 1

The error you are seeing is :

WebDriverException: Message: connection refused

As per the documentation WebDriverException is the Base webdriver exception which is as follows :

exception selenium.common.exceptions.WebDriverException(msg=None, screen=None, stacktrace=None)

So connection is refused here means that Selenium is unable to establish the connecting which you wanted to establish through :

self.driver = webdriver.Firefox(profile, log_path = logfile)

A possible solution would be to provide the complete name of the logfile along with the logical location of the logfile (from Project Level) as follows :

self.driver = webdriver.Firefox(firefox_profile=profile, log_path='./Log/geckodriver.log')

Here you can find a similar Discussion

Again, as you mentioned When I used a time.sleep(10) just before the webdriver.Firefox line, the error did not show up anymore, so I assume there was an instance of GeckoDriver and Firefox Browser client active previously. Hence, similarly as @Florent B. mentioned you have to shield your script against facing Race Around Condition which can stem out from either of the following :

• Accessing the same logfile by the new session which previous session have't released yet.
• Accessing the same port number by GeckoDriver or Marionette by the new session which previous session have't released yet.
• Lack of access to CPU
• Lack of Physical Memory
• Lack of Swap Memory
• Lack of Disc Cache
• Lack of Network Bandwidth
• Docker Image ran out of memory

Here you can find a similar Discussion.

As per the above mentioned causes, you need to follow a few steps as follows :

• Always use the latest released version of Selenium-Python client, WebDriver variant (GeckoDriver) and Web Browser (Firefox Browser)
• Always use quit() in the tearDown() method so that the webdriver and the webclient both are properly destroyed.
• Clean the Project Workspace from your IDE before and after executing your Test Suite.
• Clear the Browser Cache before and after the execution of your Tests
• Use CCleaner tool regularly to wipe away the OS chores including the stale rust_mozprofile directories.