Serilog Per Sink Filters

Posted

7/13/2023

Tags

Programming

C#

It's helpful to have all log events sent to the console to make development easier, but it's best to not have other logging sinks spammed with debug and verbose level logs.

Methods that don't work

• The usual way to filter events in Serilog is like this:

  loggerConfiguration
  	.MinimumLevel.Override("Microsoft", LogEventLevel.Warning)
  	.WriteTo.Whatever()
  	.WriteTo.Console();

  However, that will apply to all sinks, including the console.

• Another way is to apply the override inside a sub-logger:

  loggerConfiguration
  	.WriteTo.Logger(loggerConfiguration2 => loggerConfiguration2
  		.MinimumLevel.Override("Microsoft", LogEventLevel.Warning)
  		.WriteTo.Whatever())
  	.WriteTo.Console();

  However, the override will be ignored.

• Most sinks provide a restrictedToMinimumLevel option, but that applies to all log event sources.

A working method

A way that actually works is to use .Filter in a sub-logger:

loggerConfiguration
	.WriteTo.Logger(lc => lc
		// These are things like "CTRL+C to exit" messages
		// Use a sub-logger to let them go to the console, but not to the DB
		.Filter.ByExcluding(le => Matching.FromSource("Microsoft").Invoke(le)
			&& (le.Level == LogEventLevel.Verbose
				|| le.Level == LogEventLevel.Debug
				|| le.Level == LogEventLevel.Information))
		.WriteTo.Whatever())
	.WriteTo.Console();