Getting this error when trying to implement apm java agent 1.32.1 for WebClient. Issue#1306 PR#2229

@SylvainJuge Getting this error when trying to implement 1.32.1 for WebClient

`2022-07-07 14:56:18.053 ERROR 60724 — [ctor-http-nio-8] reactor.core.publisher.Operators : Operator called default onErrorDropped

java.lang.NullPointerException: null at co.elastic.apm.agent.springwebclient.WebClientSubscriber.onComplete(WebClientSubscriber.java:113) at co.elastic.apm.agent.reactor.TracedSubscriber.onComplete(TracedSubscriber.java:139) at reactor.core.publisher.FluxMap$MapSubscriber.onComplete(FluxMap.java:136) at co.elastic.apm.agent.reactor.TracedSubscriber.onComplete(TracedSubscriber.java:139) at reactor.core.publisher.FluxPeek$PeekSubscriber.onComplete(FluxPeek.java:252) at co.elastic.apm.agent.reactor.TracedSubscriber.onComplete(TracedSubscriber.java:139) at reactor.core.publisher.FluxPeek$PeekSubscriber.onComplete(FluxPeek.java:252) at co.elastic.apm.agent.reactor.TracedSubscriber.onComplete(TracedSubscriber.java:139) at reactor.core.publisher.MonoNext$NextSubscriber.onComplete(MonoNext.java:96) at reactor.core.publisher.MonoNext$NextSubscriber.onNext(MonoNext.java:77) at co.elastic.apm.agent.reactor.TracedSubscriber.onNext(TracedSubscriber.java:104) at reactor.core.publisher.MonoFlatMapMany$FlatMapManyInner.onNext(MonoFlatMapMany.java:242) at reactor.core.publisher.Operators$ScalarSubscription.request(Operators.java:2071) at reactor.core.publisher.MonoFlatMapMany$FlatMapManyMain.onSubscribeInner(MonoFlatMapMany.java:143) at reactor.core.publisher.MonoFlatMapMany$FlatMapManyInner.onSubscribe(MonoFlatMapMany.java:237) at reactor.core.publisher.MonoJust.subscribe(MonoJust.java:54) at reactor.core.publisher.MonoLiftFuseable.subscribe(MonoLiftFuseable.java:55) at reactor.core.publisher.FluxSourceMonoFuseable.subscribe(FluxSourceMonoFuseable.java:38) at reactor.core.publisher.Flux.subscribe(Flux.java:7923) at reactor.core.publisher.MonoFlatMapMany$FlatMapManyMain.onNext(MonoFlatMapMany.java:188) at co.elastic.apm.agent.reactor.TracedSubscriber.onNext(TracedSubscriber.java:104) at reactor.core.publisher.FluxRetryPredicate$RetryPredicateSubscriber.onNext(FluxRetryPredicate.java:81) at co.elastic.apm.agent.reactor.TracedSubscriber.onNext(TracedSubscriber.java:104) at reactor.core.publisher.MonoCreate$DefaultMonoSink.success(MonoCreate.java:156) at reactor.netty.http.client.HttpClientConnect$HttpObserver.onStateChange(HttpClientConnect.java:405) at reactor.netty.ReactorNetty$CompositeConnectionObserver.onStateChange(ReactorNetty.java:470) at reactor.netty.resources.PooledConnectionProvider$DisposableAcquire.onStateChange(PooledConnectionProvider.java:503) at reactor.netty.resources.PooledConnectionProvider$PooledConnection.onStateChange(PooledConnectionProvider.java:442) at reactor.netty.http.client.HttpClientOperations.onInboundNext(HttpClientOperations.java:521) at reactor.netty.channel.ChannelOperationsHandler.channelRead(ChannelOperationsHandler.java:93) at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:374) at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:360) at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:352) at io.netty.handler.timeout.IdleStateHandler.channelRead(IdleStateHandler.java:287) at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:374) at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:360) at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:352) at io.netty.handler.codec.MessageToMessageDecoder.channelRead(MessageToMessageDecoder.java:102) at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:374) at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:360) at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:352) at io.netty.channel.CombinedChannelDuplexHandler$DelegatingChannelHandlerContext.fireChannelRead(CombinedChannelDuplexHandler.java:438) at io.netty.handler.codec.ByteToMessageDecoder.fireChannelRead(ByteToMessageDecoder.java:326) at io.netty.handler.codec.ByteToMessageDecoder.fireChannelRead(ByteToMessageDecoder.java:313) at io.netty.handler.codec.ByteToMessageDecoder.callDecode(ByteToMessageDecoder.java:427) at io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:281) at io.netty.channel.CombinedChannelDuplexHandler.channelRead(CombinedChannelDuplexHandler.java:253) at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:374) at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:360) at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:352) at io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1422) at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:374) at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:360) at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:931) at io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:163) at io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:700) at io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:635) at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:552) at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:514) at io.netty.util.concurrent.SingleThreadEventExecutor$6.run(SingleThreadEventExecutor.java:1050) at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74) at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30) at java.lang.Thread.run(Thread.java:748)`

Looks like something is breaking here

_Originally posted by @anuragprakash2397 in https://github.com/elastic/apm-agent-java/pull/2229#discussion_r915689835_

[SylvainJuge]

Thanks ! That’s awesome !

That will allow us to review & merge https://github.com/elastic/apm-agent-java/pull/2708 to be included in the next release.

[anuragprakash2397]

@SylvainJuge Yes, I can reproduce the issue with a local instance. Will have to try the same with a simple spring boot app. Let me try to get the stack trace where the exception is thrown