log4net RollingFileAppender deletes all old files

Question

I have a log4net logger in an IIS-hosted WCF service. The logger is configured as a rolling file appender by size. The service is deployed to 3 different environments - QA, TEST and PROD.

The problem, which only happens on QA environment, is that no old log files are being saved. When a new log file is opened, it replaces the old file.

This is the log4net configuration from the QA environment which has the problem:

<configSections>
    <section name="log4net" type="log4net.Config.Log4NetConfigurationSectionHandler, log4net"/>
</configSections>
<log4net>
    <appender name="B2BAppender" type="log4net.Appender.RollingFileAppender, log4net">
      <!--<param name="File" type="log4net.Util.PatternString" value="Log/%property{LogName}"/>-->
      <param name="File" type="log4net.Util.PatternString" value="Log/B2BService.log"/>
      <param name="AppendToFile" value="true"/>
      <param name="RollingStyle" value="Size"/>
      <param name="MaximumFileSize" value="50KB"/>
      <param name ="MaxSizeRollBackups" value="-1"/>
      <param name="StaticLogFileName" value="true"/>
      <param name="countDirection" value="1"/>
      <param name="PreserveLogFileNameExtension" value="true"/>
      <layout type="log4net.Layout.PatternLayout, log4net">
        <param name="ConversionPattern" value="%date{dd/MM/yyyy HH:mm:ss.fff} [%level]: %message"/>
      </layout>
    </appender>
    <logger name="B2BLog">
      <level value="ALL"/>
      <appender-ref ref="B2BAppender"/>
    </logger>
</log4net>

In this environment, the file B2BService.log is being overridden every time. No old log files are preserved.

This is the log4net configuration from the PROD environment which works OK:

<configSections>
    <section name="log4net" type="log4net.Config.Log4NetConfigurationSectionHandler, log4net"/>
  </configSections>
<log4net>
    <appender name="B2BAppender" type="log4net.Appender.RollingFileAppender, log4net">
      <!--<param name="File" type="log4net.Util.PatternString" value="Log/%property{LogName}"/>-->              
      <param name="File" type="log4net.Util.PatternString" value="Log/B2BService.log"/>
      <param name="AppendToFile" value="true"/>
      <param name="RollingStyle" value="Size"/>
      <param name="MaximumFileSize" value="10MB"/>
      <param name ="MaxSizeRollBackups" value="-1"/>
      <param name="StaticLogFileName" value="true"/>
      <param name="countDirection" value="1"/>
      <param name="PreserveLogFileNameExtension" value="true"/>
      <layout type="log4net.Layout.PatternLayout, log4net">
        <param name="ConversionPattern" value="%date{dd/MM/yyyy HH:mm:ss.fff} [%level]: %message%newline"/>
      </layout>
    </appender>
    <logger name="B2BLog">
      <level value="ALL"/>
      <appender-ref ref="B2BAppender"/>
    </logger>
</log4net>

In this environment, old log files are being preserved with names B2BService.1.log, B2BService.2.log etc.

As you can see, the only differences are the MaximumFileSize (which is way too small in QA, I know, will be changed) and the ConversionPattern. Both shouldn't affect the file rolling by size.

Any ideas?

chester89 chester89 · Accepted Answer · 2014-10-07T08:27:39

May be you need to remove StaticLogFileName and PreserveFileNameExtension options (or set them to false)? Your config says 'dont keep backups, use same filename all the time' - so log4net tries it's best. Just my assumption here

log4net RollingFileAppender deletes all old files

1 Answers