Running Selenium on Windows in the Cloud

I was tasked to create a windows selenium-grid over three years ago and I still see people struggling with the same issues I ran into. There are great SAAS providers like Sauce Labs, but sometimes you need to build your own for proprietary reasons. Here is a list of gotchas that I had to work around.

Note that selenium-grid contains a hub (master) and nodes (slaves). If you are building selenium as a standalone, then substitute where I mention node with standalone.

Gotcha #1 - GUI Service

While the selenium hub can run as a windows service, that is not the case for a selenium node. Windows services run in Session 0 Isolation. This means the service can't drive the Graphical User Interface. So what do you do?

You have to start the application from a command shell. To do this, create a command file e.g., selenium.cmd to start selenium node and place it the user's startup folder:

C:\Users\<user name>\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup.

If you use Chef configuration management, the selenium cookbook can do perform this step for you.

If you use Chocolatey, the selenium package will do this for you.

Gotcha #2 - Auto Login

While windows services automatically start on server reboot, the user account won't. So how do you manage that? By setting windows registry to auto logon to that account e.g.,

[HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon]
"AutoAdminLogon"="1"
"DefaultUsername"="<user name>"
"DefaultPassword"="mypassword"
"DefaultDomainName"=""

If you use Chef configuration management, the windows_autologin cookbook can perform this step for you.

If you use Chocolatey, the autologon package will do this for you.

Gotcha #3 - Display Resolution

When running a windows server in the cloud, there is not a display device attached. This is considered headless mode. If you are on Amazon, the default resolution of the display driver can be pretty low. So how do you go about changing the default resolution? Well, create another user e.g., rdp_local and create a startup script to RDP into other user account at resolution desired e.g.,

cmdkey.exe /add:localhost /user:rdp_local /pass:"mypassword" | mstsc.exe /v localhost /w:1280 /h:1024.

You will also have to set some registry settings to enable RDP and suppress remote computer cannot be verified prompt e.g.,

[HKLM\SYSTEM\CurrentControlSet\Control\Terminal Server]
"fDenyTSConnections"=dword:00000000

[HKLM\SOFTWARE\Microsoft\Terminal Server Client]
"AuthenticationLevelOverride"=dword:000000000

Finally, add RDP firewall rule:

netsh advfirewall firewall add rule name="RDP" protocol=TCP dir=in profile=public localport=3389 remoteip=localsubnet localip=any action=allow

If you use Chef configuration management, the windows_screenresolution cookbook can perform these steps for you.

If you use Chocolatey, the screen-resolution package will do this for you.

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I hope this information helps those struggling with windows. If you have a better way of doing this, find something inaccurate, or want to share your experience, then please share via issues.