.net core 3.x 使用NLog输出日志到文件

.net core 升级到3.x，变化还是比较多，之前配置的NLog也出了问题，需要重新配置。

安装

直接在NuGet中搜索NLog.Web.AspNetCore，安装4.9+版本。

file

创建配置文件

<?xml version="1.0" encoding="utf-8" ?>
<nlog xmlns="http://www.nlog-project.org/schemas/NLog.xsd"
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      autoReload="true"
      throwExceptions="false"
      internalLogLevel="Warn"
      internalLogFile="Logs\internal-nlog.txt">

  <!-- enable asp.net core layout renderers -->
  <extensions>
    <add assembly="NLog.Web.AspNetCore"/>
  </extensions>

  <targets>
    <!-- 写入文件配置 -->
    <!-- write logs to file  -->
    <target xsi:type="File" name="allfile" fileName="Logs\nlog-all-${shortdate}.log"
            layout="${longdate}|${event-properties:item=EventId_Id}|${uppercase:${level}}|${logger}|${message} ${exception:format=tostring} ${newline}" />

    <!-- another file log, only own logs. Uses some ASP.NET core renderers -->
    <target xsi:type="File" name="ownFile-web" fileName="Logs\nlog-own-${shortdate}.log"
            layout="${longdate}|${event-properties:item=EventId_Id}|${uppercase:${level}}|${logger}|${message} ${exception:format=tostring}|url: ${aspnet-request-url}|action: ${aspnet-mvc-action} ${newline}" />
  </targets>

  <rules>
    <!--All logs, including from Microsoft-->
    <!--minlevel 改为Trace 跟踪全部 Error 只捕获异常-->
    <logger name="*" minlevel="Trace" writeTo="allfile" />

    <!--Skip non-critical Microsoft logs and so log only own logs-->
    <logger name="Microsoft.*" maxlevel="Info" final="true" /> <!-- BlackHole without writeTo -->
    <logger name="*" minlevel="Trace" writeTo="ownFile-web" />
  </rules>
</nlog>

这是官方提供的最简单的配置示例，我稍微修改了输出格式。完整配置参考官方文档。

启用拷贝到bin文件夹

<ItemGroup>
  <Content Update="nlog.config" CopyToOutputDirectory="PreserveNewest" />
</ItemGroup>

在program.cs中配置Nlog

using System;
using NLog.Web;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Hosting;

public static void Main(string[] args)
{
    var logger = NLog.Web.NLogBuilder.ConfigureNLog("nlog.config").GetCurrentClassLogger();
    try
    {
        logger.Debug("init main");
        CreateHostBuilder(args).Build().Run();
    }
    catch (Exception exception)
    {
        //NLog: catch setup errors
        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)
        NLog.LogManager.Shutdown();
    }
}

public static IHostBuilder CreateHostBuilder(string[] args) =>
    Host.CreateDefaultBuilder(args)
      .ConfigureWebHostDefaults(webBuilder =>
      {
          webBuilder.UseStartup<Startup>();
      })
      .ConfigureLogging(logging =>
      {
          // logging.ClearProviders(); // 这个方法会清空所有控制台的输出
          logging.SetMinimumLevel(Microsoft.Extensions.Logging.LogLevel.Trace);
      })
      .UseNLog(); // 使用NLog
}

这也是官方示例的例子，我把ClearProviders()方法注释掉了，因为它会清空所有控制台输出，在测试时看不到任何信息，甚至看不到启动信息，有点尴尬。。。

配置appsettings.json

{
  "Logging": {
    "IncludeScopes": false,
    "LogLevel": {
      "Default": "Trace",
      "Microsoft": "Warning",
      "Microsoft.Hosting.Lifetime": "Information"
    }
  },
  "AllowedHosts": "*"
}

使用

使用的方式和之前没有什么区别。

using Microsoft.Extensions.Logging;

public class HomeController : Controller
{
    private readonly ILogger<HomeController> _logger;

    public HomeController(ILogger<HomeController> logger)
    {
        _logger = logger;
        _logger.LogDebug(1, "发生了一个Bug");
    }

    public IActionResult Index()
    {
        _logger.LogCritical("Index中发生了一个致命的严重错误，需要马上解决");
        return View();
    }
}