Programmatic configuration of NLog in ASP.NET Core application to filter unwanted chatter? - asp.net-core

Question

I'm attempting to filter out all the unnecessary chatter from the Microsoft hosting assemblies, while still allowing Debug-level messages from our own code to pass through to our logging targets.
Here's code that configures NLog and initializes a web app. Unfortunately, the Microsoft.* and System.* namespace filtering does not functional at all. The result is that all messages Debug and higher are logged.
I do not want to use the old nlog.config process. I want to be able to build the LoggingConfiguration in code.
I really must be missing something easy here, but I don't see it!
public static void Main(string[] args)
{
// Read configuration from a variety of sources to compose our final IConfiguration
var config = ReadOurConfigFromLotsOfPlaces();
var nLogConfig = new LoggingConfiguration();
var consoleTarget = new ColoredConsoleTarget("console")
{
AutoFlush = true,
ErrorStream = true,
Layout = #"${date:format=yyyy-MM-dd HH\:mm\:ss.fff} ${level} [${logger}] - ${message}${onexception:${newline}}${exception:format=shortType,message,stackTrace:maxInnerExceptionLevel=5}"
};
nLogConfig.AddTarget(consoleTarget);
nLogConfig.LoggingRules.Add(new LoggingRule("Microsoft.*", LogLevel.Warn, consoleTarget) {Final = true});
nLogConfig.LoggingRules.Add(new LoggingRule("System.*", LogLevel.Warn, consoleTarget) {Final = true});
nLogConfig.LoggingRules.Add(new LoggingRule("*", LogLevel.Debug, consoleTarget));
var logger = NLogBuilder.ConfigureNLog(nLogConfig).GetCurrentClassLogger();
logger.Debug("NLog initialization complete");
try
{
logger.Debug("init main");
CreateHostBuilder(config).Build().Run();
}
catch (Exception exception)
{
logger.Error(exception, "Stopped program because of exception");
throw;
}
finally
{
// Ensure to flush and stop internal timers/threads before application-exit (Avoid segmentation fault on Linux)
LogManager.Shutdown();
}
}
public static IWebHostBuilder CreateHostBuilder(IConfiguration config)
{
// we don't call CreateDefaultBuilder() because we already have assembled the configuration we want to use
return new WebHostBuilder()
.UseConfiguration(config)
.UseKestrel(options => options.UseSystemd())
.UseStartup<Startup>()
.ConfigureLogging(logging =>
{
logging.ClearProviders();
logging.SetMinimumLevel(Microsoft.Extensions.Logging.LogLevel.Trace);
})
.UseNLog();
}
Any tips would be greatly appreciated.

Answer 1

Ugh. I understand my problem now: The 'LoggingRules' is looking for a positive match between logger name and the min/max level values, so my first two LoggingRule objects did not match messages coming from the Microsoft.* and System.* namespaces, so the rules did nothing with those messages.
In order to accomplish the filtering I want, this is the solution:
var nLogConfig = new LoggingConfiguration();
var consoleTarget = new ColoredConsoleTarget("console")
{
AutoFlush = true,
ErrorStream = true,
Layout = #"${date:format=yyyy-MM-dd HH\:mm\:ss.fff} ${level} [${logger}] - ${message}${onexception:${newline}}${exception:format=shortType,message,stackTrace:maxInnerExceptionLevel=5}"
};
nLogConfig.AddTarget(consoleTarget);
var nullTarget = new NullTarget("null");
nLogConfig.AddTarget(nullTarget);
// matches every Microsoft.* logger with a LogLevel less than LogLevel.Warn
nLogConfig.LoggingRules.Add(new LoggingRule("Microsoft.*", LogLevel.Trace, LogLevel.Info, nullTarget) {Final = true});
// matches every System.* logger with a LogLevel less than LogLevel.Warn
nLogConfig.LoggingRules.Add(new LoggingRule("System.*", LogLevel.Trace, LogLevel.Info, nullTarget) {Final = true});
// and everything else, LogLevel.Debug and higher
nLogConfig.LoggingRules.Add(new LoggingRule("*", LogLevel.Debug, consoleTarget));