将NLog消息写入其他目标

Question

I want to log messages to file based on a condition. For this I am first writing all the log messages to Memory type and checking the condition in my code behind. I am trying to write to file type, those stacked up (memory) logs only if the condition is true. Here is how my log looks.

<targets>

  <target name="file" xsi:type="AsyncWrapper" queueLimit="5000" overflowAction="Discard">
     <!--auto-archive above 5 MB or daily.  Max archives = 3 days
                write to <installdir>/logs/DebugLog.log--> 
    <target xsi:type="File" name="debugFile" fileName="${basedir}/logs/DebugLog.log"
                layout="${message}"
                                    archiveFileName="${basedir}/logs/archives/DebugLog-${shortdate}.{#}.txt"
                                    archiveAboveSize="5242880"
                                    archiveEvery="Day"
                                    archiveNumbering = "Rolling"
                                    maxArchiveFiles="3" />
  </target>
  <target xsi:type="Memory" name="MemoTarget" layout="${longdate} : ${message}"/>      
</targets>
<rules>
  <!-- turn logging on by setting minLevel="Debug" (no service restart necesary, it detects the setting change automatically) -->
  <logger name="*" minlevel="Debug" writeTo="MemoTarget"/>
  <logger name="MyFileLogger" minlevel="Debug" writeTo="debugFile"/>
</rules>  

Here is the code behind.

        if (dTimeRTaken > 7000)
        {
            StringBuilder stringBuilder = new StringBuilder();
            var target = (MemoryTarget)LogManager.Configuration.FindTargetByName("MemoTarget");
            var logger = LogManager.GetLogger("MyFileLogger");
            foreach (var loggingEvent in target.Logs.ToArray())
            {
                stringBuilder.AppendLine(loggingEvent);
            }                
            logger.Debug(stringBuilder);
            LogManager.Flush();
        }

The problem here is flush is not working and memory target messages are being appended. The file contents are like

1

12

123

1234

I want the output as 1 2 3 4

Answer 1

Maybe use a BufferingWrapper around your file-target. Like this:

<targets>
    <target name="memoFile" xsi:type="BufferingWrapper" bufferSize="10000" overflowAction="Discard">
       <target name="asyncFile" xsi:type="AsyncWrapper" queueLimit="5000" overflowAction="Discard">
          <target name="debugFile" xsi:type="File" fileName="${basedir}/logs/DebugLog.log">
          </target>
       </target>
    </target>
</targets>
<rules>
  <!-- MyFileLogger writes directly to file without being stalled in buffer -->
  <logger name="MyFileLogger" minlevel="Debug" writeTo="asyncFile" final="true" />
  <!-- All other loggers writes to memory buffer and waits for flush -->
  <logger name="*" minlevel="Debug" writeTo="memoFile" final="true" />
</rules>

But if you want manual control of the logevents without BufferingWrapper, then you should just ensure to configure the logging rules like this:

<rules>
  <!-- MyFileLogger writes directly to file without being stalled in buffer -->
  <logger name="MyFileLogger" minlevel="Debug" writeTo="asyncFile" final="true" />
  <!-- All other loggers writes to memory buffer and waits for flush -->
  <logger name="*" minlevel="Debug" writeTo="MemoTarget" final="true" />
</rules>