Manual:$wgDebugLogGroups/en

Details
Set to an array of log group keys to filenames. If set,  output for that group will go to that file instead of the regular. Useful for enabling selective logging in production.

Log destinations may be one of the following:


 * false to completely remove from the output, including from $wgDebugLogFile.
 * string values specifying a filename or URI.
 * associative array with keys:
 * 'destination' desired filename or URI.
 * 'sample' an integer value, specifying a sampling factor (optional)
 * 'level' A \Psr\Log\LogLevel constant, indicating the minimum level log (optional, since 1.25)

When  is set to a non-default value,   will probably be ignored, and the method of configuring log files will be determined by whatever logging system is invoked by.

Example
This example logs debug messages of group "ConfirmEditExtension" to "debug-ext_confirmedit.log" and those of group "SpamRegex" to "debug-spam.log".

Example:

Advanced example:

Some common debug log groups

 * ,,   - errors
 * - deprecation warnings
 * ,,  /  - cache
 * ,,   - database
 * - all DB queries
 * - response cookies
 * - shell commands
 * ,  - hitting rate limits ( and other)
 * ,  - ResourceLoader
 * ,  - HTTP requests to external services (via the  /  classes)
 * - API
 * ,,   - image-related
 * - job queue
 * ,  - parser
 * - warnings about pages that take long to parse
 * ,  - parser
 * - warnings about pages that take long to parse