python - Message: Unable to find a matching set of capabilities error using Selenium and GeckoDriver while loading on live server

Question

I have to build an web application on a linux webserver that will use selenium with firefox . When I run the application the the linux server "localhost:5000" it works perfectly fine . But when i tried it with "127.0.0.1:80" it is not giving me an error during webdriver loading:

driver = webdriver.Firefox(executable_path='/usr/local/bin/geckodriver')

Error:

"Message: Unable to find a matching set of capabilities"  

In nginx access.log it is producing a http 200 and there is nothing on error.log in geckodriver.log it produce:

Listening on port 41209

Environment details:

• selenium = 3.8.0
• geckodriver = 0.18.0
• Firefox version 53
• python = 3.6

nginx imageApp.conf

server {
listen 80;
server_name 127.0.0.1;

location / {
    include proxy_params;
    proxy_pass http://unix:/home/administator/imageDetectionApplication/imageDetectionApplication.sock;
    }
}

imageDetectionApplication.service

I am completely new in linux server...!!

Answer 1

This error message...

Message: Unable to find a matching set of capabilities

...implies that the GeckoDriver was unable to initiate/spawn a new Browsing Context i.e. Firefox Browser session.

Your main issue is the incompatibility between the version of the binaries you are using as follows:

• Your Selenium Client version is 3.8.0 which is almost 2.5 years older.
• Your JDK version is unknown to us.
• Your GeckoDriver version is 0.18.0 which is older.
• Your Firefox version is 53 which is also pretty old.

So there is a clear mismatch between the Selenium Client v3.8.0 , GeckoDriver v0.18.0 and the Firefox Browser v53

---

Solution

Ensure that:

• JDK is upgraded to current levels JDK 8u251.
• Selenium is upgraded to current levels Version 3.141.59.
• GeckoDriver is upgraded to GeckoDriver v0.26.0 level.
• Firefox is upgraded to current Firefox v72.0 levels.
• GeckoDriver is present in the desired location.
• GeckoDriver is having executable permission for non-root users.
• Clean your Project Workspace through your IDE and Rebuild your project with required dependencies only.
• If your base Web Client version is too old, then uninstall it install a recent GA and released version of Web Client.
• Take a System Reboot.
• Execute your Test as a non-root user.
• Always invoke driver.quit() within tearDown(){} method to close & destroy the WebDriver and Web Client instances gracefully.

---

References

You can find a couple of relevant discussions in:

• Selenium “Unable to find a matching set of capabilities” despite driver being in /usr/local/bin
• selenium.common.exceptions.SessionNotCreatedException: Message: Unable to find a matching set of capabilities with Firefox 46 through Selenium
• Selenium WebDriver, Firefox, Centos, unable to find a matching set of capabilities
• Unable to find a matching set of capabilities with selenium 3.4.3, firefox 54.0 and gecko driver 0.17
• selenium.common.exceptions.SessionNotCreatedException: Message: Unable to find a matching set of capabilities with GeckoDriver, Selenium and Firefox