After the gateway introduces skywaking, all interfaces have cross-domain problems.

[HYXBio]

When I introduced the skywalking agent in the gateway, the cross-domain problem occurred when requesting the interface through the gateway. After removing the agent, the call Interface returned to normal through the gateway. Why does this happen?

skywaking version：8.9.0
spring-cloud-alibaba-sentinel-gateway version：2.0.4.RELEASE

The following plugins are used in the agent:

The project dependency tree is as follows (old projects, the dependency tree is more confusing):

[wu-sheng]

Where it says cross domain issues?

[HYXBio]

Well, thanks for your answer.

[HYXBio]

I observed that the gateway plugin in skywalking agent has this piece of code:

Will the operation here be interception by my gateway? Then the interface cannot be requested?

[wu-sheng]

No, there are not codes would block yours.

[HYXBio]

During a certain test, I didn't roll back immediately after a cross-domain exception occurred, but waited a few minutes after running to observe whether there was an exception log and found that the following log was output.
When searching for similar information in issues, a similar exception was found:
#10029
I'm a little confused as to why the introduction of an agent would cause the project to not function properly.

2023-02-08 15:55:49.495 ERROR[[TID:N/A]] [reactor-http-client-epoll-12] [reactor.core.publisher.Operators :? ] - Operator called default onErrorDropped java.lang.NullPointerException: null at org.apache.skywalking.apm.plugin.spring.cloud.gateway.v20x.HttpClientRequestInterceptor$2.accept(HttpClientRequestInterceptor.java:88) at org.apache.skywalking.apm.plugin.spring.cloud.gateway.v20x.HttpClientRequestInterceptor$2.accept(HttpClientRequestInterceptor.java:84) at reactor.core.publisher.MonoPeekTerminal$MonoTerminalPeekSubscriber.onNext(MonoPeekTerminal.java:189) at org.springframework.cloud.sleuth.instrument.reactor.ScopePassingSpanSubscriber.onNext(ScopePassingSpanSubscriber.java:81) at reactor.core.publisher.FluxMap$MapSubscriber.onNext(FluxMap.java:108) at org.springframework.cloud.sleuth.instrument.reactor.ScopePassingSpanSubscriber.onNext(ScopePassingSpanSubscriber.java:81) at reactor.core.publisher.FluxRetryPredicate$RetryPredicateSubscriber.onNext(FluxRetryPredicate.java:81) at org.springframework.cloud.sleuth.instrument.reactor.ScopePassingSpanSubscriber.onNext(ScopePassingSpanSubscriber.java:81) at org.springframework.cloud.sleuth.instrument.reactor.ScopePassingSpanSubscriber.onNext(ScopePassingSpanSubscriber.java:81) at reactor.core.publisher.MonoCreate$DefaultMonoSink.success(MonoCreate.java:146) at reactor.ipc.netty.channel.PooledClientContextHandler.fireContextActive(PooledClientContextHandler.java:87) at reactor.ipc.netty.http.client.HttpClientOperations.onInboundNext(HttpClientOperations.java:584) at reactor.ipc.netty.channel.ChannelOperationsHandler.channelRead(ChannelOperationsHandler.java:138) at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:362) at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:348) at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:340) at io.netty.channel.CombinedChannelDuplexHandler$DelegatingChannelHandlerContext.fireChannelRead(CombinedChannelDuplexHandler.java:438) at io.netty.handler.codec.ByteToMessageDecoder.fireChannelRead(ByteToMessageDecoder.java:310) at io.netty.handler.codec.ByteToMessageDecoder.fireChannelRead(ByteToMessageDecoder.java:297) at io.netty.handler.codec.ByteToMessageDecoder.callDecode(ByteToMessageDecoder.java:413) at io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:265) at io.netty.channel.CombinedChannelDuplexHandler.channelRead(CombinedChannelDuplexHandler.java:253) at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:362) at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:348) at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:340) at io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1434) at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:362) at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:348) at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:965) at io.netty.channel.epoll.AbstractEpollStreamChannel$EpollStreamUnsafe.epollInReady(AbstractEpollStreamChannel.java:808) at io.netty.channel.epoll.EpollEventLoop.processReady(EpollEventLoop.java:410) at io.netty.channel.epoll.EpollEventLoop.run(EpollEventLoop.java:310) at io.netty.util.concurrent.SingleThreadEventExecutor$5.run(SingleThreadEventExecutor.java:884) at java.lang.Thread.run(Thread.java:748) 2023-02-08 15:55:49.498 ERROR[gateway,,,,,[TID:N/A]] [reactor-http-client-epoll-12] [r.ipc.netty.channel.ContextHandler :? ] - Error cannot be forwarded to user-facing Monoreactor.core.Exceptions$BubblingException: java.lang.NullPointerException at reactor.core.Exceptions.bubble(Exceptions.java:154) at reactor.core.publisher.Operators.onErrorDropped(Operators.java:263) at reactor.core.publisher.MonoPeekTerminal$MonoTerminalPeekSubscriber.onNext(MonoPeekTerminal.java:193) at org.springframework.cloud.sleuth.instrument.reactor.ScopePassingSpanSubscriber.onNext(ScopePassingSpanSubscriber.java:81) at reactor.core.publisher.FluxMap$MapSubscriber.onNext(FluxMap.java:108) at org.springframework.cloud.sleuth.instrument.reactor.ScopePassingSpanSubscriber.onNext(ScopePassingSpanSubscriber.java:81) at reactor.core.publisher.FluxRetryPredicate$RetryPredicateSubscriber.onNext(FluxRetryPredicate.java:81) at org.springframework.cloud.sleuth.instrument.reactor.ScopePassingSpanSubscriber.onNext(ScopePassingSpanSubscriber.java:81) at org.springframework.cloud.sleuth.instrument.reactor.ScopePassingSpanSubscriber.onNext(ScopePassingSpanSubscriber.java:81) at reactor.core.publisher.MonoCreate$DefaultMonoSink.success(MonoCreate.java:146) at reactor.ipc.netty.channel.PooledClientContextHandler.fireContextActive(PooledClientContextHandler.java:87) at reactor.ipc.netty.http.client.HttpClientOperations.onInboundNext(HttpClientOperations.java:584) at reactor.ipc.netty.channel.ChannelOperationsHandler.channelRead(ChannelOperationsHandler.java:138) at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:362) at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:348) at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:340) at io.netty.channel.CombinedChannelDuplexHandler$DelegatingChannelHandlerContext.fireChannelRead(CombinedChannelDuplexHandler.java:438) at io.netty.handler.codec.ByteToMessageDecoder.fireChannelRead(ByteToMessageDecoder.java:310) at io.netty.handler.codec.ByteToMessageDecoder.fireChannelRead(ByteToMessageDecoder.java:297) at io.netty.handler.codec.ByteToMessageDecoder.callDecode(ByteToMessageDecoder.java:413) at io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:265) at io.netty.channel.CombinedChannelDuplexHandler.channelRead(CombinedChannelDuplexHandler.java:253) at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:362) at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:348) at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:340) at io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1434) at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:362) at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:348) at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:965) at io.netty.channel.epoll.AbstractEpollStreamChannel$EpollStreamUnsafe.epollInReady(AbstractEpollStreamChannel.java:808) at io.netty.channel.epoll.EpollEventLoop.processReady(EpollEventLoop.java:410) at io.netty.channel.epoll.EpollEventLoop.run(EpollEventLoop.java:310) at io.netty.util.concurrent.SingleThreadEventExecutor$5.run(SingleThreadEventExecutor.java:884) at java.lang.Thread.run(Thread.java:748) Caused by: java.lang.NullPointerException: null at org.apache.skywalking.apm.plugin.spring.cloud.gateway.v20x.HttpClientRequestInterceptor$2.accept(HttpClientRequestInterceptor.java:88) at org.apache.skywalking.apm.plugin.spring.cloud.gateway.v20x.HttpClientRequestInterceptor$2.accept(HttpClientRequestInterceptor.java:84) at reactor.core.publisher.MonoPeekTerminal$MonoTerminalPeekSubscriber.onNext(MonoPeekTerminal.java:189) ... 31 common frames omitted

[HYXBio]

The problem is probably located.
It may be the limited viewership of the original gateway related code and configuration caused this phenomenon.
I created a new gateway and implemented all the business logic in the original gateway and removed the limited viewership of modules.
The problem with the above log disappeared.
The project uses both the limited viewership of redis and the limited viewership of sentinel.
As for why limited viewership of modules causes the above problems, it is not clear.