c# - LogManager.ReconfigExistingLoggers() doesn't update loggers archive life time

Question

Nlog.config

<nlog xmlns="http://www.nlog-project.org/schemas/NLog.xsd"
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      xsi:schemaLocation="http://www.nlog-project.org/schemas/NLog.xsd NLog.xsd"
      autoReload="true"
      throwExceptions="false"
      internalLogLevel="DEBUG" internalLogFile="temp
log-internal.log">

  
  <variable name="LogLevel" value="DEBUG"/>
  <variable name="brief" value="${longdate} | ${level} | ${logger} | ${message}"/>
  <variable name="verbose" value="${longdate} | ${machinename} | ${processid} | ${processname} | ${level} | ${logger} | ${message}"/>
  <variable name="logLifetime"  value="3"/>

  
  
  <targets >
    <target name="Global" xsi:type="File" fileName="Logs/GlobalLog.txt"  archiveNumbering="Date" enableArchiveFileCompression="true" archiveFileName="Archive/IPSlog.{#}.zip" archiveDateFormat="yyyy-MM-dd" 
     maxArchiveDays="${logLifetime}"
    archiveEvery="Day" />
    <target name="S42K" xsi:type="File" layout="${brief}" fileName="Logs/S42K.txt" archiveNumbering="Date" enableArchiveFileCompression="true" archiveFileName="Archive/S42K.{#}.zip" archiveDateFormat="yyyy-MM-dd"
    maxArchiveDays="${logLifetime}"
    archiveEvery="Day" />
    <target name="ServerApp"  xsi:type="File" archiveDateFormat="yyyy-MM-dd" archiveNumbering="Date" enableArchiveFileCompression="true" archiveFileName="Archive/IPSlog.{#}.zip" fileName="Logs/ServerApp.txt" 
     maxArchiveDays="${logLifetime}"
    archiveEvery="Day" />
    <target name="Color" xsi:type="ColoredConsole"  />

      <target name="S42KRawData" xsi:type="File" layout="${brief}" fileName="Logs/S42KRawData.txt" archiveNumbering="Date" enableArchiveFileCompression="true" archiveFileName="Archive/S42KRawData.{#}.zip" archiveDateFormat="yyyy-MM-dd"
   maxArchiveDays="${logLifetime}"
   archiveEvery="Day" />
      <target name="Advancis" xsi:type="File" layout="${brief}" fileName="Logs/Advancis.txt" archiveNumbering="Date" enableArchiveFileCompression="true" archiveFileName="Archive/Advancis.{#}.zip" archiveDateFormat="yyyy-MM-dd"
  maxArchiveDays="${logLifetime}"
  archiveEvery="Day" />
      
  </targets>

  <rules>
    <logger name="Global" minlevel="${LogLevel}"  writeTo="Global,Color" />
    <logger name="S42K" minlevel="${LogLevel}" writeTo="S42K,Color" />
    <logger name="ServerApp" minlevel="${LogLevel}" writeTo="ServerApp,Color" ></logger>
    <logger name="S42KRawData" minlevel="TRACE" writeTo="S42KRawData,Color" />
    <logger name="Advancis" minlevel="${LogLevel}" writeTo="Advancis,Color" />
    
  </rules>
</nlog>

code part when service started

 LogManager.Configuration.Variables["logLifetime"] = SetingFromINIfile.Setting[settingIterator++].Parameter;//contains "1"
LogManager.ReconfigExistingLoggers();

but loggers doesn't reconfig and use 3 days by default

Some details:

• ReconfigExistingLoggers() invoked in a task
• LogManager.Configuration.Variables["logLifetime"] return 1 after changing

what is the problem?

Answer 1

NLog Config Variables can operate in two modes:

• Static mode - ${logLifetime}
• Dynamic mode - ${var:logLifetime}

Static mode works for all types of properties independent of their type, but they will not react to runtime changes.

Dynamic mode only works for properties of the type NLog Layout. MaxArchiveDays is integer type and will not work. See also https://github.com/NLog/NLog/wiki/Var-Layout-Renderer

As a work around you can update the NLog Configuration from code, and assign the property directly on the FileTarget-objects:

var fileTargets = LogManager.Configuration.AllTargets.OfType<FileTarget>();

Another work-around would be to use autoReload="true" and just update the NLog.config file and NLog will automatically reload the configuration.