NLog - 在运行时设置记录器级别？

Question

我正在使用最新的 NLog v3.1，并且对如何在运行时设置日志记录级别有疑问。我的 NLog.config 文件中只有一个目标和记录器。记录器名称 = "*" 和 minlevel = "Info"。我在模块中有以下代码来声明记录器以及函数 GetLoggingLevel，我可以传入记录器名称以检索它的级别。但是，如何设置日志记录级别？目前我必须打开 NLog.config XML 并修改 XML 中的 minlevel。由于我有 autoReload = "true"，它会生效 - 但希望有一种方法可以使用 NLog 方法/属性来设置它。

Imports System.Xml
Imports NLog

Module modLogging

Private m_Log As Logger

Public ReadOnly Property Log As Logger
    Get
        If (m_Log Is Nothing) Then
            m_Log = LogManager.GetCurrentClassLogger
        End If
        Return m_Log
    End Get
End Property

Public Sub LogShutdown()
    LogManager.Shutdown()
End Sub

Public Function GetLoggingLevel(ByVal loggerName) As String
    Dim level As String = String.Empty

    If (LogManager.GetLogger(loggerName).IsInfoEnabled) Then
        level = "Info"
    ElseIf (LogManager.GetLogger(loggerName).IsErrorEnabled) Then
        level = "Error"
    ElseIf (LogManager.GetLogger(loggerName).IsDebugEnabled) Then
        level = "Debug"
    End If

    Return (level)
End Function

有了这个，我可以在我的项目中轻松调用 Log.Info("some text") 或 Log.Error("some error") 等。我可以获得当前级别并将其显示给用户，但我希望用户能够将日志记录级别更改为调试、信息、错误等，但我无法弄清楚如何在配置文件中设置 minlevel在运行时无需直接加载和修改配置 XML。任何帮助将不胜感激。

最诚挚的问候

Answer 1

您可以访问 LogManager.Configuration.LoggingRules 并启用或禁用特定级别的日志记录。例如，使用带有 NLog 配置的小项目：

<nlog xmlns="http://www.nlog-project.org/schemas/NLog.xsd"
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <targets>    
    <target name="consoleDetailed" 
            xsi:type="Console" 
            layout="${message}"/>
  </targets>
  <rules>
    <logger name="*" minlevel="Debug" writeTo="consoleDetailed" />
  </rules>
</nlog>  

还有一个像

这样的控制台应用程序

Sub Main()

    Dim log As Logger = LogManager.GetCurrentClassLogger

    log.Debug("debug message")
    log.Info("info message")

    For Each rule As LoggingRule In LogManager.Configuration.LoggingRules
        rule.DisableLoggingForLevel(LogLevel.Debug)
    Next

    LogManager.ReconfigExistingLoggers()

    log.Debug("debug message") REM This line will not be logged
    log.Info("info message")

    Console.ReadLine()

End Sub

Answer 2

NLog 版本。 4.6.7 使您可以这样做：

<nlog>
   <variable name="myLevel" value="Warn" />
    <rules>
      <logger minLevel="${var:myLevel}" />
    </rules>
</nlog>

然后你可以执行这段代码，它会动态更新日志规则：

LogManager.Configuration.Variables["myLevel"] = "Debug";
LogManager.ReconfigExistingLoggers();

另请参阅：https://github.com/NLog/NLog/wiki/Filtering-log-messages#semi-dynamic-routing-rules

Answer 3

您需要实现ILoggerProvider 以返回您自己的自定义记录器。您创建的记录器可以实现ILogger。您将需要复制您的 nlog 配置文件并更改最小和最大级别以允许所有日志级别。这将在一个仅用于需要不同日志记录的特殊请求的类中被覆盖。

VB：

Public NotInheritable Class CustomLevelNLogProvider
    Inherits ILoggerProvider

    Private ReadOnly factory As NLog.LogFactory

    ' pass a separate nlog config path that has logging enabled all the way to trace level, you will override it down below in the LogWrapper class
    Public Sub New(ByVal customNlogConfigPath As String)
        factory = NLog.Web.NLogBuilder.ConfigureNLog(customNlogConfigPath)
    End Sub

    Public Function CreateLogger(ByVal categoryName As String) As ILogger
        Dim logger = factory.GetLogger(categoryName)
        Return New CustomLevelLogger(logger)
    End Function
End Class

Public NotInheritable Class CustomLevelLogger
    Inherits ILogger

    Private ReadOnly innerLogger As ILogger
    Private ReadOnly minLevel As LogLevel
    Private ReadOnly maxLevel As LogLevel

    Public Sub New(ByVal innerLogger As ILogger)
        Me.innerLogger = innerLogger
    End Sub

    ' call this method on each request that needs a temporary log level
    Public Sub SetLogLevels(ByVal minLevel As LogLevel, ByVal maxLevel As LogLevel)
        Me.minLevel = minLevel
        Me.maxLevel = maxLevel
    End Sub

    ' implement the ILogger interface, making sure to use minLevel and maxLevel properly, forward calls on to innerLogger if level matches
}
End Class

C#：

public sealed class CustomLevelNLogProvider : ILoggerProvider
{
    private readonly NLog.LogFactory factory;

    // pass a separate nlog config path that has logging enabled all the way to trace level, you will override it down below in the LogWrapper class
    public CustomLevelNLogProvider(string customNlogConfigPath)
    {
        factory = NLog.Web.NLogBuilder.ConfigureNLog(customNlogConfigPath);
    }

    ' call this method on each request that needs a temporary log level
    public ILogger CreateLogger(string categoryName)
    {
        var logger = factory.GetLogger(categoryName);
        return new CustomLevelLogger(logger);
    }
}

public sealed class CustomLevelLogger : ILogger
{
    private readonly ILogger innerLogger;
    private readonly LogLevel minLevel;
    private readonly LogLevel maxLevel;

    public CustomLevelLogger(ILogger innerLogger)
    {
        this.innerLogger = innerLogger;
    }

    // call this method on each request that needs a temporary log level
    public void SetLogLevels(LogLevel minLevel, LogLevel maxLevel)
    {
        this.minLevel = minLevel;
        this.maxLevel = maxLevel;
    }

    // implement the ILogger interface, making sure to use minLevel and maxLevel properly, forward calls on to innerLogger if level matches
}