Integrate the SLF4J MDC feature

Usage

1. Add the following Tracer dependencies to your project:

   <dependency>
        <groupId>com.alipay.sofa</groupId>
        <artifactId>tracer-core</artifactId>
   </dependency>
   
   <dependency>
         <groupId>com.alipay.sofa</groupId>
         <artifactId>tracer-extensions</artifactId>
   </dependency>

2. Modify the PatternLayout property in your existing log configuration file:

   • Logback example

     <!-- This appender is an example for the Tracer MDC feature. Delete it for actual use. -->
     <appender name="MDC-EXAMPLE-APPENDER" class="ch.qos.logback.core.rolling.RollingFileAppender">
     <append>true</append>
         <filter class="ch.qos.logback.classic.filter.LevelFilter">
             <level>${logging.level}</level>
             <onMatch>ACCEPT</onMatch>
             <onMismatch>DENY</onMismatch>
         </filter>
         <file>${logging.path}/archtype-test-client/mdc-example.log</file>
         <!-- to generate a log file everyday with a longest lasting of 30 days -->
         <rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
             <!-- logfile name with daily rolling-->
                 <FileNamePattern>${logging.path}/archtype-test-client/mdc-example.log.%d{yyyy-MM-dd}</FileNamePattern>
             <!-- log preserve days-->
             <MaxHistory>30</MaxHistory>
         </rollingPolicy>
         <encoder class="ch.qos.logback.classic.encoder.PatternLayoutEncoder">
             <!--output format: %d is for date, %thread is for thread name, %-5level: loglevel with 5 characters, %msg: log message, %n: line breaker-->
             <pattern>%d{yyyy-MM-dd HH:mm:ss.SSS} [%thread] %-5level %X{SOFA-TraceId} %X{SOFA-SpanId}  %logger{50} - %msg%n</pattern>
             <!-- encoding -->
             <charset>UTF-8</charset>
         </encoder>
     </appender>
     

   • Log4j2 example

     <?xml version="1.0" encoding="UTF-8"?>
     <configuration>
         <Appenders>
             <Console name="CONSOLE" target="SYSTEM_OUT">
                 <PatternLayout pattern="%d{yyyy-MM-dd HH:mm:ss.SSS} %5p [%X{SOFA-TraceId},%X{SOFA-SpanId}] ---- %m%n "/>
             </Console>
             
             <Filename="File"fileName="./logs/test.log">
                 <PatternLayout pattern="%d{yyyy-MM-dd HH:mm:ss.SSS} %5p [%X{SOFA-TraceId},%X{SOFA-SpanId}] ---- %m%n "/>
             </File>
         </Appenders>
         <Loggers>
             <root level="info">
                 <Appender Refref="CONSOLE"/>
                 <Appender Refref="File"/>
             </root>
         </Loggers>
     </configuration>

3. Add the %X{SOFA-TraceId} and %X{SOFA-SpanId} configurations to PatternLayout:

   • %X{SOFA-TraceId}: Represents the TraceId. At runtime, this is replaced with the TraceId from the current Tracer context. If a Tracer context does not exist, it is replaced with an empty string.

   • %X{SOFA-SpanId}: Represents the SpanId. At runtime, this is replaced with the SpanId from the current Tracer context. If a Tracer context does not exist, it is replaced with an empty string.

In your application code, use the following code to print logs. No other changes are required.

logger.info("rest mdc example");

The log output is as follows:

2018-02-0515:52:45.037[SOFA-REST-WORK-3-1] INFO  0a0fe86f1517817164962100123030  MDC-EXAMPLE - rest mdc example