Dynamically reconfigure Log4Net

Question

I'm looking for tips on the best way to reconfigure the Log4Net logging level dynamically in my ASP.NET apps. I generally use a simple configuration where the root logger defines the default logging level, e.g.

<log4net>
    <root>
    <level value="INFO" />
    <appender-ref ref="..." />
    <appender-ref ref="..." />
    ... etc ...     
    </root>
    ... etc

and there may be several appenders, each with filters to define the logging levels they use.

1. The first thing I'd like to be able to do would be to allow Administrators to connect to an admin page that enables them to (a) view the current level for the root logger and (b) dynamically change it. I don't want to use "ConfigureAndWatch" and write to the configuration file on disk because I don't want these changes to persist when the application is recycled.

2. Next I'd like to go further, and on an Admin page be able to display a TreeView with all current Loggers that exist in the application, and their current logging level. And allow the administrator to be able to change the logging level selectively at any level of the hierarchy.

The idea is to to create a generic admin page that I can put into all my apps that allows administrators to selectively enable DEBUG-level logging dynamically for troubleshooting purposes.

I find the Log4Net APIs a bit confusing, can anyone point to samples or show the best way to achieve this.

Update:

Both answers are equally good so I've accepted the first - thanks. To reprise, I can get all current loggers as follows:

foreach (log4net.ILog log in log4net.LogManager.GetCurrentLoggers())
{
    log4net.Repository.Hierarchy.Logger logger = 
         (log4net.Repository.Hierarchy.Logger)log.Logger;
    Debug.WriteLine(
        String.Format("{0} Parent {1} Level {2} EffectiveLevel {3}<br>",
        logger.Name,
        logger.Parent.Name,
        logger.Level == null ? "<null>" : logger.Level.Name,
        logger.EffectiveLevel
        )
        );
}

• EffectiveLevel is the effective level - same as Level if the latter is not null, otherwise inherited from the parent.

• At least one of the loggers returned above will have the root logger as parent, which enables me to get a reference to the root logger.

With the above it should be possible to reconstruct the logger hierarchy.

Update 2

Thanks again. I've implemented an ASP.NET server control that displays the logger hierarchy in a TreeView with checkboxes, and allows the user to dynamically change the logging level at any node in the hierarchy. Works great and I'll be putting it on Admin page in all my ASP.NET Web and Web Service apps!

Answer 1

Are you looking for something like this (untested code):

foreach (ILog logger in log4net.LogManager.GetCurrentLoggers())
{
  ((log4net.Repository.Hierarchy.Logger)logger).Level = 
      log4net.Core.Level.Error;
}

You could obviously pull out the logger name, etc. in the same manner.

Answer 2

I have successfully programmatically changed the Logging level of a log4net logger, but it's not obvious how to do so from the public API. Given this Logger:

private readonly log4net.ILog mylogger;

You have to do the following fancy footwork to set it to Debug:

((log4net.Repository.Hierarchy.Logger)mylogger.Logger).Level =
 log4net.Core.Level.Debug;

For some situations -- I don't know what causes this more complicated requirement -- you may need to follow the extra steps shown in the article log4net and changing the logger levels.

Answer 3

May be not quite exactly what you want , yet:

using System;
using System.Collections.Generic;
using System.Text;
using log4net;
using log4net.Config;
using NUnit.Framework;

namespace ExampleConsoleApplication
{
  enum DebugLevel : int
  { 
    Fatal_Msgs = 0 , 
    Fatal_Error_Msgs = 1 , 
    Fatal_Error_Warn_Msgs = 2 , 
    Fatal_Error_Warn_Info_Msgs = 3 ,
    Fatal_Error_Warn_Info_Debug_Msgs = 4 
  }


    class TestClass
    {

     private static readonly ILog logger =
        LogManager.GetLogger ( typeof ( TestClass ) );


     static void Main ( string[] args )
     {
      TestClass objTestClass = new TestClass ();

      Console.WriteLine ( " START " );

      int shouldLog = 4; //CHANGE THIS FROM 0 TO 4 integer to check the functionality of the example
      //0 -- prints only FATAL messages 
      //1 -- prints FATAL and ERROR messages 
      //2 -- prints FATAL , ERROR and WARN messages 
      //3 -- prints FATAL  , ERROR , WARN and INFO messages 
      //4 -- prints FATAL  , ERROR , WARN , INFO and DEBUG messages 

      string srtLogLevel = String.Empty ; 
      switch (shouldLog)
      {
        case (int)DebugLevel.Fatal_Msgs :
          srtLogLevel = "FATAL";
          break;
        case (int)DebugLevel.Fatal_Error_Msgs:
          srtLogLevel = "ERROR";
          break;
        case (int)DebugLevel.Fatal_Error_Warn_Msgs :
          srtLogLevel = "WARN";
          break;
        case (int)DebugLevel.Fatal_Error_Warn_Info_Msgs :
          srtLogLevel = "INFO"; 
          break;
        case (int)DebugLevel.Fatal_Error_Warn_Info_Debug_Msgs :
          srtLogLevel = "DEBUG" ;
          break ;
        default:
          srtLogLevel = "FATAL";
          break;
      }

        objTestClass.SetLogingLevel ( srtLogLevel );


      objTestClass.LogSomething ();


      Console.WriteLine ( " END HIT A KEY TO EXIT " );
      Console.ReadLine ();
      } //eof method 

    /// <summary>
    /// Activates debug level 
    /// </summary>
    /// <sourceurl>http://geekswithblogs.net/rakker/archive/2007/08/22/114900.aspx&lt;/sourceurl&gt;
    private void SetLogingLevel ( string strLogLevel )
    {
     string strChecker = "WARN_INFO_DEBUG_ERROR_FATAL" ;

      if (String.IsNullOrEmpty ( strLogLevel ) == true || strChecker.Contains ( strLogLevel ) == false)
        throw new Exception ( " The strLogLevel should be set to WARN , INFO , DEBUG ," );



      log4net.Repository.ILoggerRepository[] repositories = log4net.LogManager.GetAllRepositories ();

      //Configure all loggers to be at the debug level.
      foreach (log4net.Repository.ILoggerRepository repository in repositories)
      {
        repository.Threshold = repository.LevelMap[ strLogLevel ];
        log4net.Repository.Hierarchy.Hierarchy hier = (log4net.Repository.Hierarchy.Hierarchy)repository;
        log4net.Core.ILogger[] loggers = hier.GetCurrentLoggers ();
        foreach (log4net.Core.ILogger logger in loggers)
        {
          ( (log4net.Repository.Hierarchy.Logger)logger ).Level = hier.LevelMap[ strLogLevel ];
        }
      }

      //Configure the root logger.
      log4net.Repository.Hierarchy.Hierarchy h = (log4net.Repository.Hierarchy.Hierarchy)log4net.LogManager.GetRepository ();
      log4net.Repository.Hierarchy.Logger rootLogger = h.Root;
      rootLogger.Level = h.LevelMap[ strLogLevel ];
    }

    private void LogSomething ()
    {
      #region LoggerUsage
      DOMConfigurator.Configure (); //tis configures the logger 
      logger.Debug ( "Here is a debug log." );
      logger.Info ( "... and an Info log." );
      logger.Warn ( "... and a warning." );
      logger.Error ( "... and an error." );
      logger.Fatal ( "... and a fatal error." );
      #endregion LoggerUsage

    }
    } //eof class 

} //eof namespace 






#region TheAppConfig
/*
 <?xml version="1.0" encoding="utf-8" ?>
<configuration>
    <configSections>
     <section name="log4net"
        type="log4net.Config.Log4NetConfigurationSectionHandler, log4net" />
    </configSections>
    <log4net>
     <appender name="LogFileAppender" type="log4net.Appender.FileAppender">
      <param name="File" value="LogTest2.txt" />
      <param name="AppendToFile" value="true" />
      <layout type="log4net.Layout.PatternLayout">
       <param name="Header" value="[Header] \r\n" />
       <param name="Footer" value="[Footer] \r\n" />
       <param name="ConversionPattern" value="%d [%t] %-5p %c %m%n" />
      </layout>
     </appender>

     <appender name="ColoredConsoleAppender" type="log4net.Appender.ColoredConsoleAppender">
      <mapping>
       <level value="ERROR" />
       <foreColor value="White" />
       <backColor value="Red, HighIntensity" />
      </mapping>
      <layout type="log4net.Layout.PatternLayout">
       <conversionPattern value="%date [%thread] %-5level %logger [%property{NDC}] - %message%newline" />
      </layout>
     </appender>


     <appender name="AdoNetAppender" type="log4net.Appender.AdoNetAppender">
      <connectionType value="System.Data.SqlClient.SqlConnection, System.Data, Version=1.2.10.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" />
      <connectionString value="data source=ysg;initial catalog=DBGA_DEV;integrated security=true;persist security info=True;" />
      <commandText value="INSERT INTO [DBGA_DEV].[ga].[tb_Data_Log] ([Date],[Thread],[Level],[Logger],[Message]) VALUES (@log_date, @thread, @log_level, @logger, @message)" />

      <parameter>
       <parameterName value="@log_date" />
       <dbType value="DateTime" />
       <layout type="log4net.Layout.PatternLayout" value="%date{yyyy'-'MM'-'dd HH':'mm':'ss'.'fff}" />
      </parameter>
      <parameter>
       <parameterName value="@thread" />
       <dbType value="String" />
       <size value="255" />
       <layout type="log4net.Layout.PatternLayout" value="%thread" />
      </parameter>
      <parameter>
       <parameterName value="@log_level" />
       <dbType value="String" />
       <size value="50" />
       <layout type="log4net.Layout.PatternLayout" value="%level" />
      </parameter>
      <parameter>
       <parameterName value="@logger" />
       <dbType value="String" />
       <size value="255" />
       <layout type="log4net.Layout.PatternLayout" value="%logger" />
      </parameter>
      <parameter>
       <parameterName value="@message" />
       <dbType value="String" />
       <size value="4000" />
       <layout type="log4net.Layout.PatternLayout" value="%messag2e" />
      </parameter>
     </appender>
     <root>
      <level value="INFO" />
      <appender-ref ref="LogFileAppender" />
      <appender-ref ref="AdoNetAppender" />
      <appender-ref ref="ColoredConsoleAppender" />
     </root>
    </log4net>
</configuration>
 */
#endregion TheAppconfig

//this is the xml added replace here your log4net and Nunit paths
//<Reference Include="log4net, Version=1.2.10.0, Culture=neutral, PublicKeyToken=1b44e1d426115821, processorArchitecture=MSIL">
     //  <SpecificVersion>False</SpecificVersion>
     //  <HintPath>..\..\..\Log4Net\log4net-1.2.10\bin\net\2.0\release\log4net.dll</HintPath>
     //</Reference>
     //<Reference Include="nunit.framework, Version=2.4.8.0, Culture=neutral, PublicKeyToken=96d09a1eb7f44a77, processorArchitecture=MSIL" />