现象

在spring cloud gateway中当路由无法到达时，出现SkyWalking异常

2020-10-12 15:49:12.174 ERROR 11081 --- [ctor-http-nio-4] reactor.core.publisher.Operators         : Operator called default onErrorDropped

java.lang.RuntimeException: Can not do async finish for the span repeatedly.
	at org.apache.skywalking.apm.agent.core.context.trace.AbstractTracingSpan.asyncFinish(AbstractTracingSpan.java:314)
...
2020-10-12 15:49:12.175  WARN 11081 --- [ctor-http-nio-4] io.netty.util.concurrent.DefaultPromise  : An exception was thrown by reactor.netty.FutureMono$FutureSubscription.operationComplete()

reactor.core.Exceptions$BubblingException: java.lang.RuntimeException: Can not do async finish for the span repeatedly.

分析

通过在github上的issues上搜索“Can not do async finish for the span repeatedly”发现，为已知bug，作者有计划在后续版本修复，但是在8.1.0中暂无修复。

解决方案

1. 暂时无法解决，等待作者修复。
2. 要是觉得日志烦人，可以通过logback的EvaluatorFilter日志过滤，不输出该类日志。