SpringBoot 如何在日志中增加 trace id 用于链路追踪

2021-08-23 21:30:28

目录

  1. 增加 logback 记录日志
  2. 使用 AOP 统一控制输入输出
  3. 使用 MDC 存储 trace id
项目完整代码见：https://gitee.com/zhoumengkang/wechat-demo/tree/master/strace01

增加 logback 记录日志

为什么大家都习惯用使用 logback-spring.xml而不是logback.log，因为使用前者名字，可以使用一些结合spring的特殊扩展功能。这里，暂时用不到，后面再用。

https://docs.spring.io/spring-boot/docs/2.6.1/reference/html/features.html#features.logging.logback-extensions

我们在资源目录下新建logback-spring.xml

<?xml version="1.0" encoding="UTF-8"?>
<configuration>
    <include resource="org/springframework/boot/logging/logback/defaults.xml"/>

    <property name="FILE_LOG_PATTERN" value="%d{yyyy-MM-dd HH:mm:ss.SSS} ${LOG_LEVEL_PATTERN:-%5p} ${PID:- } --- [%t] [%X{TRACE_ID}] %-40.40logger{39} : %m%n${LOG_EXCEPTION_CONVERSION_WORD:-%wEx}"/>

    <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
        <encoder>
            <pattern>${FILE_LOG_PATTERN}</pattern>
            <charset>utf8</charset>
        </encoder>
    </appender>

    <root level="INFO">
        <appender-ref ref="STDOUT" />
    </root>

</configuration>

最重要的是FILE_LOG_PATTERN日志模板里面设置了[%X{TRACE_ID}]就可以从MDC里面获取TRACE_ID的值了

使用 AOP 统一控制输入输出

@Component
@Slf4j
@Aspect
public class ControllerHandler {

    private final static String TRACE_ID = "TRACE_ID";

    @Pointcut("execution(public * com.example.demo.controller..*.*(..)) ")
    public void recordLog() {

    }

    @Before("recordLog()")
    public void before(JoinPoint point){
        MDC.put(TRACE_ID, UUID.randomUUID().toString());
    }

    @AfterReturning(pointcut = "recordLog()", returning = "responseData")
    public void after(JoinPoint point, ResponseData responseData){
        responseData.setRequestId(MDC.get(TRACE_ID));
        log.info(JSON.toJSONString(responseData));
    }
}

最重要的就是

MDC.put(TRACE_ID, UUID.randomUUID().toString());

这样就和上面日志模板里面的[%X{TRACE_ID}]对接上了。

增加一个控制器然后查看日志

@RestController
@RequestMapping("/user")
@Slf4j
public class UserController {

    @GetMapping("/{id}")
    public ResponseData<UserDTO> detail(@PathVariable Long id){
        Preconditions.checkNotNull(id, "id is null");
        
        log.info("user id:{}", id);

        UserDTO userDTO = new UserDTO();
        userDTO.setId(id);
        userDTO.setAge(20);
        userDTO.setUsername("加班写Bug");

        return ResponseData.success(userDTO);
    }
}

访问 http://localhost:8080/user/1001 查看日志

2021-12-04 21:57:34.723  INFO 48311 --- [http-nio-8080-exec-1] [aba37c62-5850-4da0-bfaf-89fa9c4282ea] c.e.demo.controller.UserController       : user id:1001
2021-12-04 21:57:34.859  INFO 48311 --- [http-nio-8080-exec-1] [aba37c62-5850-4da0-bfaf-89fa9c4282ea] com.example.demo.aop.ControllerHandler   : {"code":200,"data":{"age":20,"id":1001,"username":"加班写Bug"},"message":"OK","success":true,"traceId":"aba37c62-5850-4da0-bfaf-89fa9c4282ea"}

实际工作中，可能在访问这台 web 应用服务器之前已经有一些链路，比如有统一的网关层，或者被反向代理。trace id 的可能是需要从该应用的上游往下传递，这里以 nginx 反向代理过程中，在 header 里增加了Trace-Id字段为例

@Component
@Slf4j
@Aspect
public class ControllerHandler {

    private final static String TRACE_ID = "TRACE_ID";

    @Autowired
    HttpServletRequest request;

    @Pointcut("execution(public * com.example.demo.controller..*.*(..)) ")
    public void recordLog() {

    }

    @Before("recordLog()")
    public void before(JoinPoint point){
        if (request != null && request.getHeader("Trace-Id") != null) {
            MDC.put(TRACE_ID, request.getHeader("Trace-Id"));
        }else{
            MDC.put(TRACE_ID, UUID.randomUUID().toString());
        }
    }

    @AfterReturning(pointcut = "recordLog()", returning = "responseData")
    public void after(JoinPoint point, ResponseData responseData){
        responseData.setTraceId(MDC.get(TRACE_ID));
        log.info(JSON.toJSONString(responseData));
    }
}

使用 curl 校验下是否生效

curl -H 'Trace-Id:123456' http://localhost:8080/user/1001
{"success":true,"code":200,"message":"OK","traceId":"123456","data":{"id":1001,"username":"加班写Bug","age":20}}

这里是举例说明，trace id 可以有更多的算法来校验其是否合法。

打印更完整的链路日志

打印 trace id 不是目标，能够通过 trace id 精准的定位问题、排查问题才是目的，所以最好是 input 和 output 都打印下。这里使用Around代替了刚刚的 before 和 after ，并且对控制器的异常直接在这里做了处理。

@Component
@Slf4j
@Aspect
public class ControllerHandler {

    private final static String TRACE_ID = "TRACE_ID";

    @Autowired
    HttpServletRequest request;

    @Pointcut("execution(public * com.example.demo.controller..*.*(..)) ")
    public void recordLog() {

    }

    public void setTraceId(){
        if (request != null && request.getHeader("Trace-Id") != null) {
            MDC.put(TRACE_ID, request.getHeader("Trace-Id"));
        }else{
            MDC.put(TRACE_ID, UUID.randomUUID().toString());
        }
    }

    @Around("recordLog()")
    public Object record(ProceedingJoinPoint joinPoint) throws Throwable {

        setTraceId();

        String classType = joinPoint.getTarget().getClass().getName();
        Class<?> clazz = Class.forName(classType);
        String clazzSimpleName = clazz.getSimpleName();
        String methodName = joinPoint.getSignature().getName();
        Signature signature = joinPoint.getSignature();
        MethodSignature methodSignature = (MethodSignature) signature;
        String[] parameterNames = methodSignature.getParameterNames();
        Object[] parameters = joinPoint.getArgs();
        Map<String, Object> parameterMap = new LinkedHashMap<>();
        for (int i = 0; i < parameters.length; i++) {
            String parameterName = parameterNames[i];
            Object parameter = parameters[i];
            parameterMap.put(parameterName, parameter);
        }

        String parametersJsonString = JSON.toJSONString(parameterMap, SerializerFeature.WriteMapNullValue);
        log.info("{}#{} args:{}", clazzSimpleName, methodName, parametersJsonString);

        Object response;

        try {
            response = joinPoint.proceed(joinPoint.getArgs());
        } catch (Exception e) {
            log.error("{}#{}, exception:{}:", clazzSimpleName, methodName, e.getClass().getSimpleName(), e);

            ResponseData<Object> res = ResponseData.failure(ResponseCode.INTERNAL_ERROR);

            if (e instanceof IllegalArgumentException || e instanceof NullPointerException) {
                res.setCode(ResponseCode.BAD_REQUEST.getCode());
                res.setMessage(e.getMessage());
            }else if (e instanceof DemoRuntimeException) {
                res.setMessage(e.getMessage());
            }
            response = res;
        }

        if (response instanceof ResponseData) {
            ((ResponseData) response).setTraceId(MDC.get(TRACE_ID));
        }

        String resultJsonString = JSON.toJSONString(response, SerializerFeature.WriteMapNullValue,
                SerializerFeature.DisableCircularReferenceDetect);
        log.info("{}#{} response:{}", clazzSimpleName, methodName, resultJsonString);

        return response;
    }
    
}

99% 的应用都不用考虑这点 I/O 性能的影响，真建议打上。再次访问 http://localhost:8080/user/1001 查看日志

2021-12-04 23:24:38.122  INFO 90186 --- [http-nio-8080-exec-1] [e334594c-5ae2-48fa-91dc-10528004f6d2] com.example.demo.aop.ControllerHandler   : UserController#detail args:{"id":1001}
2021-12-04 23:24:38.141  INFO 90186 --- [http-nio-8080-exec-1] [e334594c-5ae2-48fa-91dc-10528004f6d2] c.e.demo.controller.UserController       : user id:1001
2021-12-04 23:24:38.209  INFO 90186 --- [http-nio-8080-exec-1] [e334594c-5ae2-48fa-91dc-10528004f6d2] com.example.demo.aop.ControllerHandler   : UserController#detail response:{"code":200,"data":{"age":20,"id":1001,"username":"加班写Bug"},"message":"OK","success":true,"traceId":"e334594c-5ae2-48fa-91dc-10528004f6d2"}

这样控制器里的log.info("user id:{}", id)就可以删掉了。

项目完整代码见：https://gitee.com/zhoumengkang/wechat-demo/tree/master/strace01
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