SpringBoot + MDC + Interceptor + Log4j = 給日誌添加 traceId

目的

1. 用戶的每次請求都是獨立的，爲了方便追溯，我們打出的日誌應該針對單次請求有唯一標示，就是 traceId
2. 可以通過線程 ID 來區分，但線程是可複用的。
3. 解決方法是 MDC。
4. 通過添加 filter，請求到達時，把 traceId 放到 MDC，這樣每次請求生命週期，打出的日誌就可以帶上唯一標識。

方法

1. 實現 TraceInterceptor

import java.util.UUID;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.slf4j.MDC;
import org.springframework.web.servlet.HandlerInterceptor;

public class TraceInterceptor implements HandlerInterceptor {
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        String traceId = UUID.randomUUID().toString().toUpperCase();
        MDC.put("TRACE_ID", traceId);
        return true;
    }
}

2. 註冊 Interceptor

@Configuration 註解保證 InterceptorConfig 會被 SpringBoot 作爲 bean 加載

@Configuration
public class InterceptorConfig implements WebMvcConfigurer {

    @Bean
    public TraceInterceptor initTraceInterceptor() {
        return new TraceInterceptor();
    }

    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(initTraceInterceptor()).addPathPatterns("/**");
    }
}

3. 配置 log4j2.xml

裏邊需要包含 TRACE_ID

<pattern>%d{HH:mm:ss.SSS} [%thread] %highlight(%-5level) %cyan(%logger{36}) - TRACE_ID=%X{TRACE_ID} %msg%n</pattern>

<?xml version="1.0" encoding="UTF-8"?>
<configuration scan="true" scanPeriod="120 seconds">
    <appender name="FILE_TEST" class="ch.qos.logback.core.rolling.RollingFileAppender">
        <file>/Users/charles.lin/Downloads/jingwei.log</file>
        <rollingPolicy class="ch.qos.logback.core.rolling.SizeAndTimeBasedRollingPolicy">
            <fileNamePattern>/Users/charles.lin/Downloads/%d{yyyy-MM-dd}/jingwei.%d{yyyy-MM-dd}.%i.gz
            </fileNamePattern>
            <maxFileSize>512MB</maxFileSize>
            <!-- keep 7 days' worth of history capped at 5GB total size -->
            <maxHistory>7</maxHistory>
            <totalSizeCap>5GB</totalSizeCap>
        </rollingPolicy>
        <encoder>
            <pattern>%d{HH:mm:ss.SSS} [%thread] %highlight(%-5level) %cyan(%logger{36}) - TRACE_ID=%X{TRACE_ID} %msg%n
            </pattern>
        </encoder>
    </appender>

    <appender name="console" class="ch.qos.logback.core.ConsoleAppender">
        <encoder>
            <pattern>%d{HH:mm:ss.SSS} [%thread] %highlight(%-5level) %cyan(%logger{36}) - TRACE_ID=%X{TRACE_ID} %msg%n
            </pattern>
        </encoder>
    </appender>

    <logger name="FileTest" level="INFO">
        <appender-ref ref="FILE_TEST"/>
    </logger>

    <logger name="console" level="INFO">
        <appender-ref ref="console"/>
    </logger>

    <root level="INFO">
        <appender-ref ref="console"/>
    </root>
</configuration>

4. 查看效果

20:43:48.093 [http-nio-8081-exec-2] ERROR c.a.d.p.controller.ServiceController - TRACE_ID=8905FF6C-2B8E-4412-A31A-4E3CFB04DB6D some log info