Question

• 使用maven或gradle引入toolkit依赖。

   <dependency>
      <groupId>org.apache.skywalking</groupId>
      <artifactId>apm-toolkit-log4j-2.x</artifactId>
      <version>{project.release.version}</version>
   </dependency>

• 在log4j2.xml的pattern中配置[%traceId]

   <Appenders>
      <Console name="Console" target="SYSTEM_OUT">
         <PatternLayout pattern="%d [%traceId] %-5p %c{1}:%L - %m%n"/>
      </Console>
   </Appenders>

• 支持log4j2 AsyncRoot，无需其他配置。请参阅下面的log4j2.xml演示。有关详细信息：Log4j2异步记录器

    <Configuration>
        <Appenders>
            <Console name="Console" target="SYSTEM_OUT">
                <PatternLayout pattern="%d [%traceId] %-5p %c{1}:%L - %m%n"/>
            </Console>
        </Appenders>
        <Loggers>
            <AsyncRoot level="INFO">
                <AppenderRef ref="Console"/>
            </AsyncRoot>
        </Loggers>
    </Configuration>

• 支持log4j2 AsyncAppender，不需要其他配置。请参阅下面的log4j2.xml演示。

  有关详细信息： All Loggers Async

  Log4j-2.9和更高版本要求在类路径上使用disruptor-3.3.4.jar或更高版本。在Log4j-2.9之前，需要使用interrupter-3.0.0.jar或更高版本。 这是最简单的配置，并提供最佳性能。要使所有记录器异步，请将disruptor jar添加到类路径中并且 设置系统属性 log4j2.contextSelector为 org.apache.logging.log4j.core.async.AsyncLoggerContextSelector.

  <Configuration status="WARN">
    <Appenders>
      <!-- Async Loggers will auto-flush in batches, so switch off immediateFlush. -->
      <RandomAccessFile name="RandomAccessFile" fileName="async.log" immediateFlush="false" append="false">
        <PatternLayout>
          <Pattern>%d %p %c{1.} [%t] [%traceId] %m %ex%n</Pattern>
        </PatternLayout>
      </RandomAccessFile>
    </Appenders>
    <Loggers>
      <Root level="info" includeLocation="false">
        <AppenderRef ref="RandomAccessFile"/>
      </Root>
    </Loggers>
  </Configuration>
  

  For details: Mixed Sync & Async

  Log4j-2.9 and higher require disruptor-3.3.4.jar or higher on the classpath. Prior to Log4j-2.9, disruptor-3.0.0.jar or higher was required. There is no need to set system property Log4jContextSelector to any value.

  <Configuration status="WARN">
    <Appenders>
      <!-- Async Loggers will auto-flush in batches, so switch off immediateFlush. -->
      <RandomAccessFile name="RandomAccessFile" fileName="asyncWithLocation.log"
                immediateFlush="false" append="false">
        <PatternLayout>
          <Pattern>%d %p %class{1.} [%t] [%traceId] %location %m %ex%n</Pattern>
        </PatternLayout>
      </RandomAccessFile>
    </Appenders>
    <Loggers>
      <!-- pattern layout actually uses location, so we need to include it -->
      <AsyncLogger name="com.foo.Bar" level="trace" includeLocation="true">
        <AppenderRef ref="RandomAccessFile"/>
      </AsyncLogger>
      <Root level="info" includeLocation="true">
        <AppenderRef ref="RandomAccessFile"/>
      </Root>
    </Loggers>
  </Configuration>
  

• 支持log4j2 AsyncAppender，有关详细信息： Log4j2 AsyncAppender

    <Configuration>
        <Appenders>
            <Console name="Console" target="SYSTEM_OUT">
                <PatternLayout pattern="%d [%traceId] %-5p %c{1}:%L - %m%n"/>
            </Console>
            <Async name="Async">
                <AppenderRef ref="Console"/>
            </Async>
        </Appenders>
        <Loggers>
            <Root level="INFO">
                <AppenderRef ref="Async"/>
            </Root>
        </Loggers>
    </Configuration>

• 当你使用-javaagent激活skywalking tracer后，log4j2将会输出traceId（如果存在的话）。如果tracer未激活，输出将是TID: N/A。