Config file setting for Multi appenders(file and app insight) with different log level

Question

I have requirement to log to file as well as app insight with different log levels. I have below config file setting which logs with DEBUG level in both file as well as app insight.

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <configSections>
    <section name="log4net" type="log4net.Config.Log4NetConfigurationSectionHandler, log4net" />
  </configSections>
  <log4net>
    <root>
      <level value="DEBUG"/>
      <appender-ref ref="ConsoleAppender"/>
    </root>
    <appender name="ConsoleAppender" type="log4net.Appender.ConsoleAppender">
      <level value="DEBUG" />
      <layout type="log4net.Layout.PatternLayout">
        <conversionPattern value="%utcdate [%thread] %-5level %logger - %message%newline" />
      </layout>
    </appender>
    <appender name="ApplicationInsightAppender" type="Microsoft.ApplicationInsights.Log4NetAppender.ApplicationInsightsAppender, Microsoft.ApplicationInsights.Log4NetAppender">
      <level value="ERROR" />
      <layout type="log4net.Layout.PatternLayout">
        <conversionPattern value="%utcdate [%thread] %-5level %logger - %message%newline"/>
      </layout>       
    </appender>
    <logger name ="appinsightlogger">
      <level value ="ERROR"></level>
      <appender-ref ref="ApplicationInsightAppender"/>
    </logger>
  </log4net>
</configuration>

I also tried registering both the appenders under root element like below

<root>
  <level value="DEBUG"/>
  <appender-ref ref="ConsoleAppender"/>
  <level value ="ERROR"></level>
  <appender-ref ref="ApplicationInsightAppender"/>
</root>

But still did not see required results. Can anyone help on this?

Answer 1

An appender doesn't have a level property.
Log4net notifies about this with below message.

log4net:ERROR XmlHierarchyConfigurator: Cannot find Property [level] to set object on [log4net.Appender.ConsoleAppender]

---

To have an appender log with a different level, use a filter.

Below example shows how to configure the ApplicationInsightAppender to only log errors and upwards.

<appender name="ApplicationInsightAppender" type="Microsoft.ApplicationInsights.Log4NetAppender.ApplicationInsightsAppender, Microsoft.ApplicationInsights.Log4NetAppender">
  <filter type="log4net.Filter.LevelRangeFilter">
    <levelMin value="ERROR" />
    <levelMax value="FATAL" />
  </filter>
  <layout type="log4net.Layout.PatternLayout">
    <conversionPattern value="%utcdate [%thread] %-5level %logger - %message%newline"/>
  </layout>       
</appender>

---

Full example, having the ConsoleAppender log all messages and the ApplicationInsightAppender only starting from error.

<log4net>
  <root>
    <level value="DEBUG"/>
    <appender-ref ref="ConsoleAppender" />
    <appender-ref ref="ApplicationInsightAppender" />
  </root>

  <appender name="ConsoleAppender" type="log4net.Appender.ConsoleAppender">
    <layout type="log4net.Layout.PatternLayout">
      <conversionPattern value="%utcdate [%thread] %-5level %logger - %message%newline" />
    </layout>
  </appender>

  <appender name="ApplicationInsightAppender" type="Microsoft.ApplicationInsights.Log4NetAppender.ApplicationInsightsAppender, Microsoft.ApplicationInsights.Log4NetAppender">
    <filter type="log4net.Filter.LevelRangeFilter">
      <levelMin value="ERROR" />
      <levelMax value="FATAL" />
    </filter>
    <layout type="log4net.Layout.PatternLayout">
      <conversionPattern value="%utcdate [%thread] %-5level %logger - %message%newline"/>
    </layout>       
  </appender>
</log4net>