Manual:$wgDebugLogFile/zh

细节
The file name of the debug log, or empty if disabled. appends to this file.

It is also used for structured logging, when a message goes to a channel that is not otherwise configured.

注释
If the debug file gets too big, some servers will generate an internal server error until you delete said file.

If the file isn't generated after doing some requests to the server, check if the webserver has permissions to write on that location, and if PHP can access that file (normally restricted by the  directive).

参见

 * Manual:How to debug#Logging