This is the only way I know how to do this in log4net. We do this to
handle remote logging from embedded controllers. We use .NET remoting
appenders in this case, so we get the HostName property of each remote
host logging to the sink. But if you're local you could do the same
thing with a string filter or other property filter. This gives you
individual layout control over each appender, and hence each log source.

If only log4net would add in a layout-ref tag so we wouldn't have to
repeat ourselves 75 times...


<log4net>
<appender name="ConsoleAppender" type="log4net.Appender.ConsoleAppender">
<layout type="log4net.Layout.PatternLayout">
<param name="ConversionPattern" value="%property{log4net:HostName}
%d{MM/dd/yyyy HH:mm:ss.fff} [%p] %c{1}: %m%n" />
</layout>
</appender>

<appender name="Comp1" type="log4net.Appender.RollingFileAppender">
<file value="Comp1/Comp1.log" />
<staticLogFileName value="true" />
<filter type="log4net.Filter.PropertyFilter">
<Key value="log4net:HostName" />
<StringToMatch value="Comp1" />
</filter>
<filter type="log4net.Filter.DenyAllFilter" />
<appendToFile value="true" />
<rollingStyle value="Date" />
<datePattern value="yyyyMMdd’.log’" />
<layout type="log4net.Layout.PatternLayout">
<param name="ConversionPattern" value="%d{MM/dd/yyyy HH:mm:ss.fff} [%p]
%c{1}: %m%n" />
</layout>
</appender>

<appender name="Comp2" type="log4net.Appender.RollingFileAppender">
<file value="Comp2/Comp2.log" />
<staticLogFileName value="true" />
<filter type="log4net.Filter.PropertyFilter">
<Key value="log4net:HostName" />
<StringToMatch value="Comp2" />
</filter>
<filter type="log4net.Filter.DenyAllFilter" />
<appendToFile value="true" />
<rollingStyle value="Date" />
<datePattern value="yyyyMMdd" />
<layout type="log4net.Layout.PatternLayout">
<param name="ConversionPattern" value="%d{MM/dd/yyyy HH:mm:ss.fff} [%p]
%c{1}: %m%n" />
</layout>
</appender>

<appender name="Comp3" type="log4net.Appender.RollingFileAppender">
<file value="Comp3/Comp3.log" />
<staticLogFileName value="true" />
<filter type="log4net.Filter.PropertyFilter">
<Key value="log4net:HostName" />
<StringToMatch value="Comp3" />
</filter>
<filter type="log4net.Filter.DenyAllFilter" />
<appendToFile value="true" />
<rollingStyle value="Date" />
<datePattern value="yyyyMMdd" />
<layout type="log4net.Layout.PatternLayout">
<param name="ConversionPattern" value="%d{MM/dd/yyyy HH:mm:ss.fff} [%p]
%c{1}: %m%n" />
</layout>
</appender>

...

<root>
<level value="ALL" />
<appender-ref ref="ConsoleAppender" />
<appender-ref ref="Comp1" />
<appender-ref ref="Comp2" />
<appender-ref ref="Comp3" />
...
</root>
</log4net>

If you don't want to type the same pattern over and over, extend PatternLayout and provide your own default pattern:

 <layout type="Company.Logging.MyPatternLayout, Company.Logging" />

That can be overridden when necessary:

 <layout type="Company.Logging.MyPatternLayout, Company.Logging">
  <conversionPattern" value="%d %m%n" />
 </layout>

You can also extend RollingFileAppender and set default values in there:

 <appender name="Comp1" type="Company.Logging.CompRollingFileAppender, Company.Logging">
  <comp value="1"/>
 </appender>
 <appender name="Comp2" type="Company.Logging.CompRollingFileAppender, Company.Logging">

<comp value="2"/>
 </appender>
 <appender name="Comp3" type="Company.Logging.CompRollingFileAppender, Company.Logging">

<comp value="3"/>
  <layout type="Company.Logging.MyPatternLayout, Company.Logging">
   <conversionPattern" value="%d %m%n" />
  </layout>
 </appender>
 <appender name="Comp4" type="Company.Logging.CompRollingFileAppender, Company.Logging">

<comp value="4"/>
 </appender>