ASP.NET Core Web App log 404 requests as warning

user_98491 0
Viewed 1789

If I create a new ASP.NET Core Web App (Model-View-Controller) with dotnet new mvc it has already logging configured out of the box.

However, http request error codes are logged as info event.

info: Microsoft.AspNetCore.Hosting.Internal.WebHost[1]
      Request starting HTTP/1.1 GET https://localhost:5001/doesnotexists
info: Microsoft.AspNetCore.Hosting.Internal.WebHost[2]
      Request finished in 4.4052ms 404

Is it possible to changed this behaviour to (4xx -> warning, 5xx -> error) .i.e by investigating and rewriting log events.

I already read https://docs.microsoft.com/en-us/aspnet/core/fundamentals/logging/?view=aspnetcore-2.2

this looked promissing but I didn't find a hook for this purpose

    var webHost = new WebHostBuilder()
        .UseKestrel()
        .UseContentRoot(Directory.GetCurrentDirectory())
        .ConfigureLogging((hostingContext, logging) =>
        {
            // investigate and rewrite log event
        })
        .UseStartup<Startup>()
        .Build()
asp.net-core logging asp.net c#
2 Answers

Single line solution

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;

using Microsoft.Extensions.Logging;

namespace temp
{
    public class Startup
    {    
        public void Configure(IApplicationBuilder app, IHostEnvironment env, ILogger<Startup> logger)
        {

            ...

            app.UseStatusCodePages(async context =>
            {
                var code = context.HttpContext.Response.StatusCode;
                if (code == 404) {
                    logger.Log(LogLevel.Error, null, "log message");
                }
            });

            ...

        }
    }
}
user_73883070

You need to implement your own ILogger and ILoggerProvider.

A simple demo like:

  1. CustomLogger 

        public class CustomLogger : ILogger
    {
        public CustomLogger() { }

        public IDisposable BeginScope<TState>(TState state)=> NullScope.Instance;

        public bool IsEnabled(LogLevel logLevel) => true;

        public void Log<TState>(
            LogLevel logLevel,
            EventId eventId,
            TState state,
            Exception exception,
            Func<TState, Exception, string> formatter
        )
        {

            var msg = formatter(state, exception);
            if (msg.Contains("404"))
            {
                logLevel = LogLevel.Warning;
            }

            Console.WriteLine($"{ GetLogLevelString(logLevel) } : { eventId } { msg } { exception }");
        }
        private static string GetLogLevelString(LogLevel logLevel)
        {
            switch (logLevel)
            {
                case LogLevel.Trace:
                    return "trce";
                case LogLevel.Debug:
                    return "dbug";
                case LogLevel.Information:
                    return "info";
                case LogLevel.Warning:
                    return "warn";
                case LogLevel.Error:
                    return "fail";
                case LogLevel.Critical:
                    return "crit";
                default:
                    throw new ArgumentOutOfRangeException(nameof(logLevel));
            }
        }

    }

  2. CustomLoggerProvider 

    public class CustomLoggerProvider : ILoggerProvider
{
    public ILogger CreateLogger(string categoryName)
    {
        return new CustomLogger();
    }

    public void Dispose()
    {

    }
}

  3. Register above code 

            public static IWebHostBuilder CreateWebHostBuilder(string[] args) =>
            WebHost.CreateDefaultBuilder(args)
                .UseStartup<Startup>()
                .ConfigureLogging(config => {
                    config.ClearProviders();
                    config.AddProvider(new CustomLoggerProvider());
                });

    You could check Logging and implement your own log provider.

user_62656200
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