作为技术人员的我们，应该如何有效的书写日志，如何更好地查看日志，如何有效地定位BUG呢？ 我希望您花时间看完，这对您的职业生涯将有非常大的帮助。

什么是Nlog

NLog is a flexible and free logging platform for various .NET platforms, including .NET standard. NLog makes it easy to write to several targets. (database, file, console) and change the logging configuration on-the-fly.

NLog是一个灵活的、免费的日志记录平台，适用于各种。net平台，包括。net标准平台。NLog使写入多个目标变得容易。(数据库、文件、控制台)，并动态更改日志记录配置。

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为什么推荐使用它

很多开发人在编写程序代码时，常常忘记处理异常 try catch ，导致没有记录异常日志，在bug来临时，无处安放的小手这才开始try catch

  • Nlog可以检测系统引发的异常，自动记录日志，避免我们忘记try catch
  • 同时支持自定义日志模板、写入渠道等
  • 还支持写入seq，一种微服务的日志服务框架

如何使用

1、在 csproj 中手动添加依赖项或使用 NuGet 添加依赖项

<ItemGroup>
  <PackageReference Include="NLog.Web.AspNetCore" Version="4.*" />
  <PackageReference Include="NLog" Version="4.*" />
</ItemGroup>

2、创建一个配置文件。

在项目的根目录中创建 nlog.config（全部小写）文件。
我们使用这个例子：

<?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"
      internalLogLevel="Info"
      internalLogFile="c:\temp\internal-nlog-AspNetCore.txt">

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

  <!-- the targets to write to -->
  <targets>
    <!-- File Target for all log messages with basic details -->
    <target xsi:type="File" name="allfile" fileName="c:\temp\nlog-AspNetCore-all-${shortdate}.log"
            layout="${longdate}|${event-properties:item=EventId_Id:whenEmpty=0}|${level:uppercase=true}|${logger}|${message} ${exception:format=tostring}" />

    <!-- File Target for own log messages with extra web details using some ASP.NET core renderers -->
    <target xsi:type="File" name="ownFile-web" fileName="c:\temp\nlog-AspNetCore-own-${shortdate}.log"
            layout="${longdate}|${event-properties:item=EventId_Id:whenEmpty=0}|${level:uppercase=true}|${logger}|${message} ${exception:format=tostring}|url: ${aspnet-request-url}|action: ${aspnet-mvc-action}|${callsite}" />

    <!--Console Target for hosting lifetime messages to improve Docker / Visual Studio startup detection -->
    <target xsi:type="Console" name="lifetimeConsole" layout="${MicrosoftConsoleLayout}" />
  </targets>

  <!-- rules to map from logger name to target -->
  <rules>
    <!--All logs, including from Microsoft-->
    <logger name="*" minlevel="Trace" writeTo="allfile" />

    <!--Output hosting lifetime messages to console target for faster startup detection -->
    <logger name="Microsoft.Hosting.Lifetime" minlevel="Info" writeTo="lifetimeConsole, ownFile-web" final="true" />

    <!--Skip non-critical Microsoft logs and so log only own logs (BlackHole) -->
    <logger name="Microsoft.*" maxlevel="Info" final="true" />
    <logger name="System.Net.Http.*" maxlevel="Info" final="true" />
    
    <logger name="*" minlevel="Trace" writeTo="ownFile-web" />
  </rules>
</nlog>

有关配置文件的更多详细信息，请单击此处。
Configuration options

3、更新程序

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

namespace ASP.NET_Core_5_NLog_Example
{
    public class Program
    {
        public static void Main(string[] args)
        {
            var logger = NLog.LogManager.Setup().LoadConfigurationFromAppSettings().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();
                    logging.SetMinimumLevel(LogLevel.Trace);
                })
                .UseNLog();  // NLog: Setup NLog for Dependency injection
    }
}

4、写入日志

将 ILogger 注入控制器：

using Microsoft.Extensions.Logging;

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

    public HomeController(ILogger<HomeController> logger)
    {
        _logger = logger;
        _logger.LogDebug(1, "NLog injected into HomeController");
    }

    public IActionResult Index()
    {
        _logger.LogInformation("Hello, this is the index!");
        return View();
    }

6、示例输出

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使用appsettings.json配置Nlog

https://github.com/NLog/NLog.Extensions.Logging/wiki/NLog-configuration-with-appsettings.json

以下是我已经配置好的json ，可直接拷贝使用

"Logging": {
   "LogLevel": {
     "Default": "Debug",
     "System": "Warning",
     "Microsoft": "Warning",
     "Hangfire": "Warning"
   },
   "NLog": {
     "IncludeScopes": true //true启用nlog  ，false 禁用
   }
 },
 "NLog": {
   "autoReload": true,
   "throwConfigExceptions": true,
   "internalLogLevel": "Info",
   "internalLogFile": "logs/internal-nlog.txt", //修改项目名称即可
   "extensions": [
     {
       "assembly": "NLog.Extensions.Logging"
     },
     {
       "assembly": "NLog.Web.AspNetCore"
     },
     { 
       "assembly": "NLog.Targets.Seq"
     }
   ],
   "variables": {
     "var_logdir": "logs" //修改项目名称即可
   },
   "time": {
     "type": "AccurateUTC"
   },
   "default-wrapper": {
     "type": "AsyncWrapper",
     "overflowAction": "Block"
   },
   "targets": {
     "all-file": {
       "type": "File",
       "fileName": "${var_logdir}/nlog-all-${shortdate}.log",
       "layout": {
         "type": "JsonLayout",
         "Attributes": [
           {
             "name": "eventId",
             "layout": "${event-properties:item=EventId_Id:whenEmpty=0}"
           },
           {
             "name": "time",
             "layout": "${longdate}"
           },
           {
             "name": "level",
             "layout": "${level:upperCase=true}"
           },
           {
             "name": "message",
             "layout": "${message}",
             "escapeUnicode": false,
             "escapeForwardSlash": false,
             "includeEmptyValue": true
           },
           {
             "name": "httpRequestId",
             "layout": "${aspnet-traceidentifier}",
             "escapeUnicode": false,
             "escapeForwardSlash": false,
             "includeEmptyValue": true
           },
           {
             "name": "url",
             "layout": "${aspnet-request-url}",
             "escapeUnicode": false,
             "escapeForwardSlash": false,
             "includeEmptyValue": true
           },
           {
             "name": "method",
             "layout": "${aspnet-request-method}",
             "escapeUnicode": false,
             "escapeForwardSlash": false,
             "includeEmptyValue": true
           },
           {
             "name": "queryString",
             "layout": "${aspnet-request-querystring}",
             "escapeUnicode": false,
             "escapeForwardSlash": false,
             "includeEmptyValue": true
           },
           {
             "name": "referrer",
             "layout": "${aspnet-request-referrer}",
             "escapeUnicode": false,
             "escapeForwardSlash": false,
             "includeEmptyValue": true
           },
           {
             "name": "host",
             "layout": "${aspnet-request-host}",
             "escapeUnicode": false,
             "escapeForwardSlash": false,
             "includeEmptyValue": true
           },
           {
             "name": "serverIp",
             "layout": "${local-ip}",
             "escapeUnicode": false,
             "escapeForwardSlash": false,
             "includeEmptyValue": true
           },
           {
             "name": "clientIp",
             "layout": "${aspnet-request-ip}",
             "escapeUnicode": false,
             "escapeForwardSlash": false,
             "includeEmptyValue": true
           },
           {
             "name": "iisSiteName",
             "layout": "${iis-site-name}",
             "escapeUnicode": false,
             "escapeForwardSlash": false,
             "includeEmptyValue": true
           },
           {
             "name": "responseCode",
             "layout": "${aspnet-response-statuscode}",
             "escapeUnicode": false,
             "escapeForwardSlash": false,
             "includeEmptyValue": true
           },
           {
             "name": "identity",
             "layout": "${aspnet-user-identity}",
             "escapeUnicode": false,
             "escapeForwardSlash": false,
             "includeEmptyValue": true
           },
           {
             "name": "exception",
             "layout": "${exception:format=tostring}",
             "escapeUnicode": false,
             "escapeForwardSlash": false,
             "includeEmptyValue": true
           }
         ]
       }
     },
     "own-console": {
       "type": "LimitingWrapper",
       "interval": "00:00:01",
       "messageLimit": 100,
       "target": {
         "type": "ColoredConsole",
         "layout": "${longdate}|${event-properties:item=EventId_Id:whenEmpty=0}|${uppercase:${level}}|${logger}|${message} ${exception:format=tostring}|${callsite}",
         "rowHighlightingRules": [
           {
             "condition": "level == LogLevel.Error",
             "foregroundColor": "Red"
           },
           {
             "condition": "level == LogLevel.Fatal",
             "foregroundColor": "Red",
             "backgroundColor": "White"
           },
           {
             "condition": "level == LogLevel.Info",
             "foregroundColor": "Blue"
           },
           {
             "condition": "level == LogLevel.Warning",
             "foregroundColor": "Yellow"
           }
         ]
       }
     },
     "seq": {
       "type": "BufferingWrapper",
       "bufferSize": 200,
       "flushTimeout": 2000,
       "slidingTimeout": false,
       "target": {
         "type": "Seq",
         "serverUrl": "http://192.168.1.227:5341/", //修改接受地址即可  http://dev.iduo.cc:8008/
         "apiKey": "d2Zt3M8OZCtgUVkjctyx", //修改ApiKey 即可
         "properties": [
           {
             "name": "eventId",
             "value": "${event-properties:item=EventId_Id:whenEmpty=0}"
           },
           {
             "name": "time",
             "value": "${longdate}"
           },
           {
             "name": "level",
             "value": "${level:upperCase=true}"
           },
           {
             "name": "message",
             "value": "${message}"
           },
           {
             "name": "httpRequestId",
             "value": "${aspnet-traceidentifier}"
           },
           {
             "name": "url",
             "value": "${aspnet-request-url}"
           },
           {
             "name": "method",
             "value": "${aspnet-request-method}"
           },
           {
             "name": "queryString",
             "value": "${aspnet-request-querystring}"
           },
           {
             "name": "referrer",
             "value": "${aspnet-request-referrer}"
           },
           {
             "name": "host",
             "value": "${aspnet-request-host}"
           },
           {
             "name": "serverIp",
             "value": "${local-ip}"
           },
           {
             "name": "clientIp",
             "value": "${aspnet-request-ip}"
           },
           {
             "name": "iisSiteName",
             "value": "${iis-site-name}"
           },
           {
             "name": "responseCode",
             "value": "${aspnet-response-statuscode}"
           },
           {
             "name": "exception",
             "value": "${exception:format=tostring}"
           }
         ]
       }
     }
   },
   "rules": [
     //{
     //  "logger": "*",
     //  "minLevel": "Info",
     //  "writeTo": "all-file"
     //},
     {
       "logger": "*",
       "minLevel": "Error",
       "writeTo": "own-console"
     },
     //{
     //  "logger": "*",
     //  "minLevel": "Info",
     //  "writeTo": "seq"
     //}
   ]
 }

对接Seq

部署

开放 5340 和 5341 端口

docker部署命令

docker run \
--name seq \
-d \
--restart unless-stopped \ 
-e ACCEPT_EULA=Y \
-v /home/administrator/applogs:/data \
-p 5340:80 \
-p 5341:5341 \
datalust/seq

此参数是seq日志文件存放路径，根据实际情况做出调整

-v /home/administrator/applogs:/data

程序修改

安装NuGet包 NLog.Targets.Seq

5341端口是写入日志的接口，换掉时，对应的appsetting.json 里 seq的 配置地址Nlog:targets:seq:serverUrl也需要变化。

针对每个项目使用不同的apiKey Nlog:targets:seq:apiKey

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示例效果

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