Can Log4net have multiple appenders write to the same file?

Question

I\'m using a RollingFileAppender to log some info to a file with a conversionPattern (in the web.config) that looks like this for the header of each log section:

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Answer 1

Yes you can have two log4net appenders that append (write) to the same log file.

You need to place the following line in each of your Appenders:

<lockingModel type="log4net.Appender.FileAppender+MinimalLock" />

This will make log4net use a minimal locking model that allows multiple processes to write to the same file.

Here's an example XML that uses two appenders writing to the same log file:

<log4net debug="false">
<appender name="RollingLogFileAppender1" type="log4net.Appender.RollingFileAppender">
  <!-- this configures a log for the application messages -->
  <file value="TestLog.log" />
  <appendToFile value="true" />
  <!-- next line uses a minimal locking model that allows multiple processes to write to the same file -->
  <lockingModel type="log4net.Appender.FileAppender+MinimalLock" />
  <rollingStyle value="Size" />
  <maxSizeRollBackups value="10" />
  <maximumFileSize value="10MB" />
  <staticLogFileName value="true" />
  <!-- make the most recent log the highest numbered log -->
  <countDirection value="1" />
  <layout type="log4net.Layout.PatternLayout">
    <conversionPattern value="%-5level %date{MM-dd-yyyy HH:mm:ss.ff} [%property{NDC}] %message%newline [Thread: %thread] %c{1} Method:%method(%file{1}, Line:%line) %newline" />
  </layout>
  <!-- The following two filters insure only log requests of 
        version '1' use this Appender -->
</appender>
<appender name="RollingLogFileAppender2" type="log4net.Appender.RollingFileAppender">
  <file value="TestLog.log" />
  <appendToFile value="true" />
  <!-- next line uses a minimal locking model that allows multiple processes to write to the same file -->
  <lockingModel type="log4net.Appender.FileAppender+MinimalLock" />
  <rollingStyle value="Size" />
  <maxSizeRollBackups value="10" />
  <maximumFileSize value="10MB" />
  <staticLogFileName value="true" />
  <!-- make the most recent log the highest numbered log -->
  <countDirection value="1" />
  <layout type="log4net.Layout.PatternLayout">
    <conversionPattern value="%-5level %date{MM-dd-yyyy HH:mm:ss.ff} [%property{NDC}] [Thread: %thread] %c{1} Method:%method(%file{1}, Line:%line) %newline%message" />
  </layout>
</appender>
<root>
  <level value="DEBUG" />
  <appender-ref ref="RollingLogFileAppender1" />
  <appender-ref ref="RollingLogFileAppender2" />
</root>

This can be found in the Apache documentation here: Apache Log4Net Docs Just search on this page for 'same file'.

Hope this helps.

Answer 2

You could realize if there is any problem with log4net checking the output window on visual studio. The library log errors there, very useful to detect configuration mistakes.