SpringCloudGateway Skywalking 不打印tid

环境

jar包	版本
jdk	17
spring-cloud-gateway	3.1.8
spring-webflux	5.3.28
apm-toolkit-logback-1.x	9.2.0
logback-classic	1.2.12
skywalking-agent	9.2.0

日志pattern

-%clr(%d{${LOG_DATEFORMAT_PATTERN:-yyyy-MM-dd HH:mm:ss.SSS}}){faint} %clr(${LOG_LEVEL_PATTERN:-%5p}) [%X{tid}] %clr(${PID:- }){magenta} %clr(---){faint} %clr([%15.15t]){faint} %clr(%-40.40logger{39}:%line){cyan} %clr(:){faint} %m%n${LOG_EXCEPTION_CONVERSION_WORD:-%wEx}

---

现象

其他服务正常，只有gateway的日志中不打印tid，但是查看skywalking的后台，可以看到gateway服务已经在链路上了，并且生成了tid。

非常细致的描述：Spring cloud gateway project logback cannot print TraceID · Issue #5906 · apache/skywalking (github.com)

解决

搜索了一下发现很多人都遇到了同样的问题，而官方的处理方法比较冷淡！以下方法经过验证是有效的！

1. 确认添加了插件。从skywalking-agent目录下的optional-plugins中复制apm-spring-cloud-gateway-3.x-plugin-9.2.0.jar和apm-spring-webflux-5.x-plugin-9.2.0.jar到plugins目录
2. 添加3个类，其中MdcSubscriber和LogHooks是必须的，它们将链路id写进了MDC的traceId字段中，SkywalkingUtil通过主动的方式向MDC中传入traceId，是为了解决自定义日志类AccessLogGlobalFilter的输出问题，如果你没有这个filter，可以不用第3个类。代码如下：

MdcSubscriber:

package tench.supx.infra.gateway;

import cn.hutool.core.bean.BeanUtil;
import org.reactivestreams.Subscription;
import org.slf4j.MDC;
import reactor.core.CoreSubscriber;
import reactor.util.context.Context;

import java.util.Optional;

public class MdcSubscriber implements CoreSubscriber {

    private static final String TRACE_ID = "traceId";

    private static final String SKYWALKING_CTX_SNAPSHOT = "SKYWALKING_CONTEXT_SNAPSHOT";

    private final CoreSubscriber<Object> actual;

    public MdcSubscriber(CoreSubscriber<Object> actual) {
        this.actual = actual;
    }

    @Override
    public void onSubscribe(Subscription s) {
        actual.onSubscribe(s);
    }

    @Override
    public void onNext(Object o) {
        Context c = actual.currentContext();
        Optional<String> traceIdOptional = Optional.empty();
        if (!c.isEmpty() && c.hasKey(SKYWALKING_CTX_SNAPSHOT)) {
            traceIdOptional = Optional.of(c.get(SKYWALKING_CTX_SNAPSHOT)).map(BeanUtil::beanToMap)
                    .map(t -> t.get(TRACE_ID)).map(BeanUtil::beanToMap).map(t -> t.get("id")).map(Object::toString);
        }
        try (MDC.MDCCloseable cMdc = MDC.putCloseable(TRACE_ID, traceIdOptional.orElse("N/A"))) {
            actual.onNext(o);
        }
    }

    @Override
    public void onError(Throwable throwable) {
        actual.onError(throwable);
    }

    @Override
    public void onComplete() {
        actual.onComplete();
    }

    @Override
    public Context currentContext() {
        return actual.currentContext();
    }
}

LogHooks:

package tech.supx.infra.gateway;

import org.springframework.stereotype.Component;
import reactor.core.publisher.Operators;

import javax.annotation.PostConstruct;
import javax.annotation.PreDestroy;

@Component
public class LogHooks {

    private static final String KEY = "logMdc";

    @PostConstruct
    @SuppressWarnings("unchecked")
    public void setHook() {
        reactor.core.publisher.Hooks.onEachOperator(KEY,
                Operators.lift((scannable, coreSubscriber) -> new MdcSubscriber(coreSubscriber)));
    }

    @PreDestroy
    public void resetHook() {
        reactor.core.publisher.Hooks.resetOnEachOperator(KEY);
    }

}

SkywalkingUtil:

package tech.supx.infra.gateway;

import cn.hutool.core.util.ObjectUtil;
import lombok.extern.slf4j.Slf4j;
import org.slf4j.MDC;
import org.springframework.web.server.ServerWebExchange;

import java.lang.reflect.Field;
import java.lang.reflect.Method;

@Slf4j
public class SkywalkingUtil {

    /**
     * tid放入MDC
     *
     * @param exchange
     */
    public static void putTidIntoMdc(ServerWebExchange exchange) {
        putTidIntoMdc(exchange, "tid");
    }

    /**
     * tid放入MDC
     *
     * @param exchange
     */
    public static void putTidIntoMdc(ServerWebExchange exchange, String key) {
        try {
            Object entrySpanInstance = exchange.getAttributes().get("SKYWALKING_SPAN");
            if (ObjectUtil.isEmpty(entrySpanInstance)) {
                return;
            }
            Class<?> entrySpanClazz = entrySpanInstance.getClass().getSuperclass().getSuperclass();
            Field field = entrySpanClazz.getDeclaredField("owner");
            field.setAccessible(true);
            Object ownerInstance = field.get(entrySpanInstance);
            Class<?> ownerClazz = ownerInstance.getClass();
            Method getTraceId = ownerClazz.getMethod("getReadablePrimaryTraceId");
            String traceId = (String) getTraceId.invoke(ownerInstance);
            MDC.put(key, traceId);
        } catch (Exception e) {
            log.error("gateway追踪码获取失败", e);
        }
    }

}

3. 最后一步，调整日志的pattern，输出traceId。e.g：[%X{traceId}]

可能用到的依赖

<dependency>
    <groupId>cn.hutool</groupId>
    <artifactId>hutool-all</artifactId>
    <version>5.8.27</version>
</dependency>

参考：

1. SpringCloudGateway使用Skywalking时日志打印traceId - 简书 (jianshu.com)
2. 解决SkyWalking在gateway中logback链路丢失 | Both Savage