Log4net: Skeleton of (app/web).config File

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Introduction

In log4net first article, Log4net: How to setup and use at first time, I explained very basic steps to setup and use log4net for logging.

In this article, I am going to detail a very basic structure of app.config/web.config file for log4net.

Config Section for Log4net

You already know that after adding log4net.dll in application type project, you will be adding config-section for log4net in configuration file as follows:

<configSections>
    <section name="log4net" type="log4net.Config.Log4NetConfigurationSectionHandler, log4net"/>
</configSections>

Sample App.config

And this is a sample of app.config file to clearly understand log4net config-setup:

<log4net>
   <appender name="B_SampleRollingAppenderTest" type="log4net.Appender.RollingFileAppender">
     <param name="CountDirection" value="1"/>
     <param name="threshold" value="DEBUG"/>
     <datePattern>_dd_MMMM_yyyy_dddd_HH_mm</datePattern>
     <dateTimeStrategy type="log4net.Appender.RollingFileAppender+LocalDateTime"/>
     <maximumFileSize>100KB</maximumFileSize>
     <preserveLogFileNameExtension>true</preserveLogFileNameExtension>
     <rollingStyle>date</rollingStyle>
     <file type="log4net.Util.PatternString" value="%envFolderPath{Desktop}\RahulLog.txt"/>
     <immediateFlush>true</immediateFlush>
     <param name="layout" type="log4net.Layout.PatternLayout">
       <param name="conversionPattern">
         MyLoggerName: %stacktracedetail{5},%newline  %identity
         %newline [AppDomain_a] = %2.4a . %newline [AppDomainFull] = %2.4appdomain .
         %newline [AppSetting1] = %2.4appsetting . %newline [AppSetting2] = %AppSetting .
         %newline [AppSetting3] = %appSetting . %newline [LocalDate_d] = %2.4d .
         %newline [LocalDate_Full] = %2.4date . %newline [EnvironmentFolderPath] = %2.4envFolderPath .
         %newline [Environment] = %env . %newline [Identity_u] = %2.4u .
         %newline [Identity_Full] = %2.4identity . %newline [Literal] = %literal .
         %newline [New-Line_Full] = %newline . %newline [New-Line_n] = %n .
         %newline [ProcessId] = %2.4processid . %newline [Property_P] = %P .
         %newline [Property_Full] = %2.4property . %newline [Property_Plural] = %2.4properties .
         %newline [Property_X] = %2.4X . %newline [Property_mdc] = %2.4mdc .
         %newline [RandomString] = %2.4random . %newline [User_w] = %2.4w .
         %newline [User_Full] = %2.4username . %newline [Utc_Time1] = %2.4utcdate .
         %newline [Utc_Time2] = %2.4utcDate . %newline [Utc_Time3] = %2.4UtcDate .
         %newline [AspNet-Cache_Data] = %aspnet-cache .
         %newline [AspNetContextData] = %aspnet-context .
         %newline [AspNetRequest] = %aspnet-request . %newline [AspNetSession] = %aspnet-session .
         %newline [Logger_c] = %2.4c . %newline [Logger_Full] = %2.4logger .
         %newline [TypeName_C] = %2.4C . %newline [TypeName_class] = %2.4class .
         %newline [TypeName_type] = %2.4type . %newline [Exception] = %2.4exception. %newline %newline
         %newline %2.4exception{message} %newline --> %2.4exception{source}
         %newline --> %2.4exception{stacktrace} %newline --> %2.4exception{targetsite}
         %newline --> %2.4exception{helplink}  . %newline [File_F] = %2.4F .
         %newline File_Full] = %2.4file . %newline [Location_l] = %2.4l .
         %newline [Location_Full] = %2.4location . %newline [LineNumber_L] = %2.4L .
         %newline [LineNumber_line] = %2.4line . %newline [Message_m] = %2.4m .
         %newline [Message_message] = %2.4message . %newline [Method_M] = %2.4M .
         %newline [Method_Method] = %2.4method . %newline [LogLevel_p] = %2.4p .
         %newline [LogLevel_Level] = %2.4level . %newline [RelativeTime_r] = %2.4r .
         %newline [RelativeTime_timestamp] = %2.4timestamp . %newline [StackTrace] = %2.4stacktrace .
         %newline [Thread_t] = %2.4t . %newline [Thread_Full] = %2.4thread .
         %newline [NDC_x] = %2.4x . %newline [NDC_Full] = %2.4ndc .
         %newline [stacktracedetail] = %2.4stacktracedetail .
       </param>
     </param>
     <lockingModel type="log4net.Appender.FileAppender+MinimalLock"/>
   </appender>
   <appender name="EventLogAppender_A" type="log4net.Appender.EventLogAppender">
     <param name="threshold" value="DEBUG"/>
     <category value="1"/>
     <applicationName  type="log4net.Util.PatternString">%2.4appsetting{Name1}</applicationName>
     <mapping>
       <eventLogEntryType value="Error"/>
       <level value="Error"/>
     </mapping>
     <mapping>
       <eventLogEntryType value="Warning"/>
       <level value="Warn"/>
     </mapping>
     <mapping>
       <eventLogEntryType value="Information"/>
       <level value="Info"/>
     </mapping>
     <mapping>
       <eventLogEntryType value="SuccessAudit"/>
       <level value="Debug"/>
     </mapping>
     <mapping>
       <eventLogEntryType value="FailureAudit"/>
       <level value="Fatal"/>
     </mapping>
     <eventId>23</eventId>
     <logName type="log4net.Util.PatternString">Rahul1</logName>
     <layout type="log4net.Layout.DynamicPatternLayout">
       <header value="%newline**** Trace Opened Local:
       %date{yyyy-MM-dd HH:mm:ss.fff} UTC: %utcdate{yyyy-MM-dd HH:mm:ss.fff} ****%newline"/>
       <footer value="**** Trace Closed %date{yyyy-MM-dd HH:mm:ss.fff} ****%newline"/>
       <conversionPattern value="%newline Logged Message : %message"/>
     </layout>
     <securityContext type="log4net.Util.WindowsSecurityContext">
       <credentials>user</credentials>
       <domainName>Domain</domainName>
       <password>welcom@123</password>
       <userName>TESTUser</userName>
     </securityContext>
   </appender>
   <root>
     <level value="DEBUG"/>
     <appender-ref ref="B_SampleRollingAppenderTest"/>
   </root>
 </log4net>

Now there is a parent tag log4net and inside this log4net tag, one root tag and one or many appender tags will be added.

So let’s start first with log4net tag.

<log4net> tag

This is actually a root tag for log4net setup in config file. We define all appenders and one child tag named root inside it.

Attributes

I am talking about its main attribute threshold here, which is used mostly.

Threshold

This attribute is used to define log-level based filtering on log messages like which level of log messages should be written to target and which should be ignored simply.

Common behavior of this property for all possible values:

Log-Level Possible Values

You can log messages with level other than popular levels (DEBUG, INFO, WARN, ERROR, FATAL) by below implementation in SampleLog4NetLogger class:

public void Log(Level logLevel, object message, Exception exceptionData)
        {
            log4NetReal.Logger.Log(null, logLevel, message, exceptionData);
        }

How to Set It in app.config

We define threshold on log4net tag like below:

<log4net threshold="ALL">

<appender> Tag

This is the tag, by which, we define/configure an instance of any type of appender.

How to Set It in app.config

<appender name="B_SampleRollingAppenderTest" type="log4net.Appender.RollingFileAppender">
      <param name="CountDirection" value="1"/>
      <param name="threshold" value="DEBUG"/>
      <maximumFileSize>100KB</maximumFileSize>
      <preserveLogFileNameExtension>true</preserveLogFileNameExtension>
      <rollingStyle>size</rollingStyle>
      <file type="log4net.Util.PatternString" value="..\..\Logs\RahulLog.txt"/>
      <immediateFlush>true</immediateFlush>
      <layout type="log4net.Layout.PatternLayout">
        <conversionPattern value="%newline Logged Message : %message %newline "/>
      </layout>
      <lockingModel type="log4net.Appender.FileAppender+MinimalLock"/>
    </appender>

As this tag defines the instance of specific type of appender, so there are 2 mandatory attributes available on this tag:

1. Type

This attribute is used to define appender type for instantiation. We define namespace qualified full name of appender class in it.

Common behavior of this property for all possible values:

2. Name

This property is used to define name of appender instance. It could be any string value. Name of each instance should be unique in that app.config file.

Common behavior of this property for all possible values:

<root> tag

<root> tag is used to define all active appenders for logging and apply log-level based filter on all those active appenders uniformly.

Inside <root> tag, we define below child tags:

Appender-ref:

As we can define n-number of instances of more than one type of appender (provided by log4net) inside <log4net> tag, this property is used to define only active appender instances to be considered for logging each incoming message.

There could be one or more than one <appender-ref> tags inside <root> tag to represent each active appender instance individually.

Appender instances which are defined inside <log4net> tag, but not declared in <root> tag won’t be executed at all.

Common behavior of this property for all possible values:

How to Set It in app.config

<root> <level value="DEBUG"/> 
<appender-ref ref="SampleRollingAppenderTest"/> 
<appender-ref ref="B_SampleRollingAppenderTest"/> </root>

Level

This property is used to define log-level filtering on log messages for only active appender instances defined inside <root> tag.

Common behavior of this property for all possible values:

It’s possible values and behavior are already defined in <log4net> threshold section above. (Refer to the table captioned "Log-Level Possible Values" above).

How to Set It in app.config

<root>
      <level value="DEBUG"/>
      <appender-ref ref="SampleRollingAppenderTest"/>
      <appender-ref ref="B_SampleRollingAppenderTest"/>
</root>

So, this is the very basic structure of configuration file for log4net setup.

Points of Interest

By exploring log4net, I tried to explore the basic structure of configuration for log4net. As there are many things done in this file for the same, so detailing all these helps me to remember such complex things for a long time.