@RequestBody raises IllegalStateException for form data

[kichewko-giga]

Affects: Spring Boot 2.1.3.RELEASE

---

Hello!

I noticed something interesting. When you make a mistake in WebFlux application, you don't see real exception, instead you see the same exception every-time:

2019-02-27 16:41:41.686 ERROR 28059 --- [or-http-epoll-1] a.w.r.e.AbstractErrorWebExceptionHandler : [2af64f7c] 500 Server Error for HTTP POST "/hello"

java.lang.IllegalStateException: Only one connection receive subscriber allowed.
        at reactor.netty.channel.FluxReceive.startReceiver(FluxReceive.java:271) ~[reactor-netty-0.8.5.RELEASE.jar:0.8.5.RELEASE]
        at reactor.netty.channel.FluxReceive.subscribe(FluxReceive.java:121) ~[reactor-netty-0.8.5.RELEASE.jar:0.8.5.RELEASE]
        at reactor.core.publisher.FluxMap.subscribe(FluxMap.java:62) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.FluxOnAssembly.subscribe(FluxOnAssembly.java:132) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.netty.ByteBufFlux.subscribe(ByteBufFlux.java:294) ~[reactor-netty-0.8.5.RELEASE.jar:0.8.5.RELEASE]
        at reactor.core.publisher.FluxPeek.subscribe(FluxPeek.java:83) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.FluxOnAssembly.subscribe(FluxOnAssembly.java:132) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.netty.ByteBufFlux.subscribe(ByteBufFlux.java:294) ~[reactor-netty-0.8.5.RELEASE.jar:0.8.5.RELEASE]
        at reactor.core.publisher.FluxMap.subscribe(FluxMap.java:62) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.FluxOnAssembly.subscribe(FluxOnAssembly.java:132) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.MonoCollectList.subscribe(MonoCollectList.java:59) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.MonoOnAssembly.subscribe(MonoOnAssembly.java:56) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.MonoFilterFuseable.subscribe(MonoFilterFuseable.java:44) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.MonoOnAssembly.subscribe(MonoOnAssembly.java:56) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.MonoMapFuseable.subscribe(MonoMapFuseable.java:56) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.MonoOnAssembly.subscribe(MonoOnAssembly.java:56) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
...

Example controller:

package app.controllers;

import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class HelloWorld {

    @PostMapping("/hello")
    public String handle(@RequestBody String body)  {
        System.out.printf("\n\n\nbody: %s\n\n\n\n", body);
        return "Hello WebFlux";
    }
}

If you make correct request you will see correct response:

$ curl -i -w "\n\n" -XPOST -d "asd" -H "Content-Type: application/json" http://localhost:8080/hello
HTTP/1.1 200 OK
Content-Type: text/plain;charset=UTF-8
Content-Length: 13

Hello WebFlux

If you make a mistake you will receive 500 and lot's of logs that don't tell you what has happened:

curl -i -w "\n\n" -XPOST -d "asd" http://localhost:8080/hello
HTTP/1.1 500 Internal Server Error
Content-Type: application/json;charset=UTF-8
Content-Length: 16111

{"timestamp":"2019-02-27T16:12:13.095+0000","path":"/hello","status":500,"error":"Internal Server Error","message":"Only one connection receive subscriber allowed.","trace":"java.lang.IllegalStateException: Only one connection receive subscriber allowed.\n\tat reactor.netty.channel.FluxReceive.startReceiver(FluxReceive.java:271)\n\tat reactor.netty.channel.FluxReceive.subscribe(FluxReceive.java:121)\n\tat reactor.core.publisher.FluxMap.subscribe(FluxMap.java:62)\n\tat reactor.core.publisher.FluxOnAssembly.subscribe(FluxOnAssembly.java:132)\n\tat reactor.netty.ByteBufFlux.subscribe(ByteBufFlux.java:294)\n\tat 

...

You can see the same exception in application logs:

2019-02-27 17:12:13.109 ERROR 32312 --- [or-http-epoll-3] a.w.r.e.AbstractErrorWebExceptionHandler : [8aba656e] 500 Server Error for HTTP POST "/hello"

java.lang.IllegalStateException: Only one connection receive subscriber allowed.
        at reactor.netty.channel.FluxReceive.startReceiver(FluxReceive.java:271) ~[reactor-netty-0.8.5.RELEASE.jar:0.8.5.RELEASE]
        at reactor.netty.channel.FluxReceive.subscribe(FluxReceive.java:121) ~[reactor-netty-0.8.5.RELEASE.jar:0.8.5.RELEASE]
        at reactor.core.publisher.FluxMap.subscribe(FluxMap.java:62) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.FluxOnAssembly.subscribe(FluxOnAssembly.java:132) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.netty.ByteBufFlux.subscribe(ByteBufFlux.java:294) ~[reactor-netty-0.8.5.RELEASE.jar:0.8.5.RELEASE]
        at reactor.core.publisher.FluxPeek.subscribe(FluxPeek.java:83) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.FluxOnAssembly.subscribe(FluxOnAssembly.java:132) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.netty.ByteBufFlux.subscribe(ByteBufFlux.java:294) ~[reactor-netty-0.8.5.RELEASE.jar:0.8.5.RELEASE]
        at reactor.core.publisher.FluxMap.subscribe(FluxMap.java:62) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.FluxOnAssembly.subscribe(FluxOnAssembly.java:132) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.MonoCollectList.subscribe(MonoCollectList.java:59) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.MonoOnAssembly.subscribe(MonoOnAssembly.java:56) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.MonoFilterFuseable.subscribe(MonoFilterFuseable.java:44) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.MonoOnAssembly.subscribe(MonoOnAssembly.java:56) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.MonoMapFuseable.subscribe(MonoMapFuseable.java:56) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.MonoOnAssembly.subscribe(MonoOnAssembly.java:56) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.MonoSubscriberContext.subscribe(MonoSubscriberContext.java:47) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.MonoMapFuseable.subscribe(MonoMapFuseable.java:59) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.MonoOnAssembly.subscribe(MonoOnAssembly.java:61) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.MonoOnErrorResume.subscribe(MonoOnErrorResume.java:44) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.MonoOnAssembly.subscribe(MonoOnAssembly.java:61) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.MonoSwitchIfEmpty.subscribe(MonoSwitchIfEmpty.java:44) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.MonoOnAssembly.subscribe(MonoOnAssembly.java:61) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.MonoDefaultIfEmpty.subscribe(MonoDefaultIfEmpty.java:37) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.MonoOnAssembly.subscribe(MonoOnAssembly.java:61) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.MonoPeekFuseable.subscribe(MonoPeekFuseable.java:74) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.MonoOnAssembly.subscribe(MonoOnAssembly.java:61) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.Mono.subscribe(Mono.java:3694) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.MonoZip.subscribe(MonoZip.java:128) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.MonoOnAssembly.subscribe(MonoOnAssembly.java:61) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.MonoFlatMap.subscribe(MonoFlatMap.java:60) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.MonoOnAssembly.subscribe(MonoOnAssembly.java:61) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.MonoDefer.subscribe(MonoDefer.java:52) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.MonoOnAssembly.subscribe(MonoOnAssembly.java:61) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.MonoIgnoreThen$ThenIgnoreMain.drain(MonoIgnoreThen.java:153) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.MonoIgnoreThen.subscribe(MonoIgnoreThen.java:56) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.MonoOnAssembly.subscribe(MonoOnAssembly.java:61) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.MonoPeekFuseable.subscribe(MonoPeekFuseable.java:74) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.MonoOnAssembly.subscribe(MonoOnAssembly.java:61) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.MonoPeekFuseable.subscribe(MonoPeekFuseable.java:74) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.MonoOnAssembly.subscribe(MonoOnAssembly.java:61) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.MonoOnErrorResume.subscribe(MonoOnErrorResume.java:44) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.MonoOnAssembly.subscribe(MonoOnAssembly.java:61) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.MonoFlatMap$FlatMapMain.onNext(MonoFlatMap.java:150) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.FluxOnAssembly$OnAssemblySubscriber.onNext(FluxOnAssembly.java:353) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.FluxSwitchIfEmpty$SwitchIfEmptySubscriber.onNext(FluxSwitchIfEmpty.java:67) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.FluxOnAssembly$OnAssemblySubscriber.onNext(FluxOnAssembly.java:353) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.MonoNext$NextSubscriber.onNext(MonoNext.java:76) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.FluxOnAssembly$OnAssemblySubscriber.onNext(FluxOnAssembly.java:353) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.FluxConcatMap$ConcatMapImmediate.innerNext(FluxConcatMap.java:275) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.FluxConcatMap$ConcatMapInner.onNext(FluxConcatMap.java:849) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.FluxOnAssembly$OnAssemblySubscriber.onNext(FluxOnAssembly.java:353) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.FluxMap$MapSubscriber.onNext(FluxMap.java:114) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.FluxOnAssembly$OnAssemblySubscriber.onNext(FluxOnAssembly.java:353) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.Operators$ScalarSubscription.request(Operators.java:2070) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.FluxOnAssembly$OnAssemblySubscriber.request(FluxOnAssembly.java:438) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.FluxMap$MapSubscriber.request(FluxMap.java:155) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.FluxOnAssembly$OnAssemblySubscriber.request(FluxOnAssembly.java:438) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.Operators$MultiSubscriptionSubscriber.set(Operators.java:1878) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.Operators$MultiSubscriptionSubscriber.onSubscribe(Operators.java:1752) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.FluxOnAssembly$OnAssemblySubscriber.onSubscribe(FluxOnAssembly.java:422) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.FluxMap$MapSubscriber.onSubscribe(FluxMap.java:86) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.FluxOnAssembly$OnAssemblySubscriber.onSubscribe(FluxOnAssembly.java:422) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.MonoJust.subscribe(MonoJust.java:54) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.MonoCallableOnAssembly.subscribe(MonoCallableOnAssembly.java:82) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.MonoMap.subscribe(MonoMap.java:55) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.MonoOnAssembly.subscribe(MonoOnAssembly.java:61) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.Mono.subscribe(Mono.java:3694) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.FluxConcatMap$ConcatMapImmediate.drain(FluxConcatMap.java:442) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.FluxConcatMap$ConcatMapImmediate.onSubscribe(FluxConcatMap.java:212) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.FluxOnAssembly$OnAssemblySubscriber.onSubscribe(FluxOnAssembly.java:422) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.FluxIterable.subscribe(FluxIterable.java:139) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.FluxIterable.subscribe(FluxIterable.java:63) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.FluxOnAssembly.subscribe(FluxOnAssembly.java:132) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.FluxConcatMap.subscribe(FluxConcatMap.java:121) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.FluxOnAssembly.subscribe(FluxOnAssembly.java:132) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.MonoNext.subscribe(MonoNext.java:40) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.MonoOnAssembly.subscribe(MonoOnAssembly.java:61) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.MonoSwitchIfEmpty.subscribe(MonoSwitchIfEmpty.java:44) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.MonoOnAssembly.subscribe(MonoOnAssembly.java:61) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.MonoFlatMap.subscribe(MonoFlatMap.java:60) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.MonoOnAssembly.subscribe(MonoOnAssembly.java:61) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.MonoFlatMap.subscribe(MonoFlatMap.java:60) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.MonoOnAssembly.subscribe(MonoOnAssembly.java:61) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.MonoDefer.subscribe(MonoDefer.java:52) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.MonoOnAssembly.subscribe(MonoOnAssembly.java:61) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.MonoFlatMap$FlatMapMain.onNext(MonoFlatMap.java:150) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.FluxOnAssembly$OnAssemblySubscriber.onNext(FluxOnAssembly.java:353) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.FluxMapFuseable$MapFuseableSubscriber.onNext(FluxMapFuseable.java:121) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.FluxOnAssembly$OnAssemblySubscriber.onNext(FluxOnAssembly.java:353) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.Operators$MonoSubscriber.complete(Operators.java:1505) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.MonoProcessor.onNext(MonoProcessor.java:389) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.FluxOnAssembly$OnAssemblySubscriber.onNext(FluxOnAssembly.java:353) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.FluxSwitchIfEmpty$SwitchIfEmptySubscriber.onNext(FluxSwitchIfEmpty.java:67) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.FluxOnAssembly$OnAssemblySubscriber.onNext(FluxOnAssembly.java:353) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.FluxMapFuseable$MapFuseableSubscriber.onNext(FluxMapFuseable.java:121) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.FluxContextStart$ContextStartSubscriber.onNext(FluxContextStart.java:103) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.FluxOnAssembly$OnAssemblySubscriber.onNext(FluxOnAssembly.java:353) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.FluxMapFuseable$MapFuseableConditionalSubscriber.onNext(FluxMapFuseable.java:287) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.FluxOnAssembly$OnAssemblySubscriber.onNext(FluxOnAssembly.java:353) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.FluxFilterFuseable$FilterFuseableConditionalSubscriber.onNext(FluxFilterFuseable.java:331) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.FluxOnAssembly$OnAssemblySubscriber.onNext(FluxOnAssembly.java:353) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.Operators$MonoSubscriber.complete(Operators.java:1505) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.MonoCollectList$MonoBufferAllSubscriber.onComplete(MonoCollectList.java:118) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.FluxOnAssembly$OnAssemblySubscriber.onComplete(FluxOnAssembly.java:363) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.FluxMap$MapSubscriber.onComplete(FluxMap.java:136) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.FluxOnAssembly$OnAssemblySubscriber.onComplete(FluxOnAssembly.java:363) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.FluxPeek$PeekSubscriber.onComplete(FluxPeek.java:252) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.FluxOnAssembly$OnAssemblySubscriber.onComplete(FluxOnAssembly.java:363) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.core.publisher.FluxMap$MapSubscriber.onComplete(FluxMap.java:136) ~[reactor-core-3.2.6.RELEASE.jar:3.2.6.RELEASE]
        at reactor.netty.channel.FluxReceive.terminateReceiver(FluxReceive.java:372) ~[reactor-netty-0.8.5.RELEASE.jar:0.8.5.RELEASE]
        at reactor.netty.channel.FluxReceive.drainReceiver(FluxReceive.java:196) ~[reactor-netty-0.8.5.RELEASE.jar:0.8.5.RELEASE]
        at reactor.netty.channel.FluxReceive.onInboundComplete(FluxReceive.java:337) ~[reactor-netty-0.8.5.RELEASE.jar:0.8.5.RELEASE]
        at reactor.netty.channel.ChannelOperations.onInboundComplete(ChannelOperations.java:334) ~[reactor-netty-0.8.5.RELEASE.jar:0.8.5.RELEASE]
        at reactor.netty.http.server.HttpServerOperations.onInboundNext(HttpServerOperations.java:453) ~[reactor-netty-0.8.5.RELEASE.jar:0.8.5.RELEASE]
        at reactor.netty.channel.ChannelOperationsHandler.channelRead(ChannelOperationsHandler.java:141) ~[reactor-netty-0.8.5.RELEASE.jar:0.8.5.RELEASE]
        at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:362) ~[netty-transport-4.1.33.Final.jar:4.1.33.Final]
        at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:348) ~[netty-transport-4.1.33.Final.jar:4.1.33.Final]
        at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:340) ~[netty-transport-4.1.33.Final.jar:4.1.33.Final]
        at reactor.netty.http.server.HttpTrafficHandler.channelRead(HttpTrafficHandler.java:191) ~[reactor-netty-0.8.5.RELEASE.jar:0.8.5.RELEASE]
        at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:362) ~[netty-transport-4.1.33.Final.jar:4.1.33.Final]
        at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:348) ~[netty-transport-4.1.33.Final.jar:4.1.33.Final]
        at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:340) ~[netty-transport-4.1.33.Final.jar:4.1.33.Final]
        at io.netty.channel.CombinedChannelDuplexHandler$DelegatingChannelHandlerContext.fireChannelRead(CombinedChannelDuplexHandler.java:438) ~[netty-transport-4.1.33.Final.jar:4.1.33.Final]
        at io.netty.handler.codec.ByteToMessageDecoder.fireChannelRead(ByteToMessageDecoder.java:323) ~[netty-codec-4.1.33.Final.jar:4.1.33.Final]
        at io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:297) ~[netty-codec-4.1.33.Final.jar:4.1.33.Final]
        at io.netty.channel.CombinedChannelDuplexHandler.channelRead(CombinedChannelDuplexHandler.java:253) ~[netty-transport-4.1.33.Final.jar:4.1.33.Final]
        at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:362) ~[netty-transport-4.1.33.Final.jar:4.1.33.Final]
        at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:348) ~[netty-transport-4.1.33.Final.jar:4.1.33.Final]
        at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:340) ~[netty-transport-4.1.33.Final.jar:4.1.33.Final]
        at io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1408) ~[netty-transport-4.1.33.Final.jar:4.1.33.Final]
        at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:362) ~[netty-transport-4.1.33.Final.jar:4.1.33.Final]
        at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:348) ~[netty-transport-4.1.33.Final.jar:4.1.33.Final]
        at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:930) ~[netty-transport-4.1.33.Final.jar:4.1.33.Final]
        at io.netty.channel.epoll.AbstractEpollStreamChannel$EpollStreamUnsafe.epollInReady(AbstractEpollStreamChannel.java:799) ~[netty-transport-native-epoll-4.1.33.Final-linux-x86_64.jar:4.1.33.Final]
        at io.netty.channel.epoll.EpollEventLoop.processReady(EpollEventLoop.java:427) ~[netty-transport-native-epoll-4.1.33.Final-linux-x86_64.jar:4.1.33.Final]
        at io.netty.channel.epoll.EpollEventLoop.run(EpollEventLoop.java:328) ~[netty-transport-native-epoll-4.1.33.Final-linux-x86_64.jar:4.1.33.Final]
        at io.netty.util.concurrent.SingleThreadEventExecutor$5.run(SingleThreadEventExecutor.java:905) ~[netty-common-4.1.33.Final.jar:4.1.33.Final]
        at java.lang.Thread.run(Thread.java:748) ~[na:1.8.0_201]
        Suppressed: reactor.core.publisher.FluxOnAssembly$OnAssemblyException: 
Assembly trace from producer [reactor.core.publisher.FluxMap] :
        reactor.core.publisher.Flux.map(Flux.java:5689)
        reactor.netty.ByteBufFlux.fromInbound(ByteBufFlux.java:70)
Error has been observed by the following operator(s):
        |_      Flux.map ⇢ reactor.netty.ByteBufFlux.fromInbound(ByteBufFlux.java:70)
        |_      Flux.doOnNext ⇢ reactor.netty.ByteBufFlux.retain(ByteBufFlux.java:282)
        |_      Flux.map ⇢ org.springframework.http.server.reactive.ReactorServerHttpRequest.getBody(ReactorServerHttpRequest.java:166)
        |_      Flux.collectList ⇢ org.springframework.core.io.buffer.DataBufferUtils.join(DataBufferUtils.java:438)
        |_      Mono.filter ⇢ org.springframework.core.io.buffer.DataBufferUtils.join(DataBufferUtils.java:439)
        |_      Mono.map ⇢ org.springframework.core.io.buffer.DataBufferUtils.join(DataBufferUtils.java:440)
        |_      Mono.map ⇢ org.springframework.core.codec.AbstractDataBufferDecoder.decodeToMono(AbstractDataBufferDecoder.java:68)
        |_      Mono.error ⇢ org.springframework.web.reactive.result.method.annotation.AbstractMessageReaderArgumentResolver.lambda$readBody$4(AbstractMessageReaderArgumentResolver.java:186)
        |_      Mono.onErrorResume ⇢ org.springframework.web.reactive.result.method.annotation.AbstractMessageReaderArgumentResolver.readBody(AbstractMessageReaderArgumentResolver.java:186)
        |_      Mono.switchIfEmpty ⇢ org.springframework.web.reactive.result.method.annotation.AbstractMessageReaderArgumentResolver.readBody(AbstractMessageReaderArgumentResolver.java:188)
        |_      Mono.defaultIfEmpty ⇢ org.springframework.web.reactive.result.method.InvocableHandlerMethod.getMethodArgumentValues(InvocableHandlerMethod.java:192)
        |_      Mono.doOnError ⇢ org.springframework.web.reactive.result.method.InvocableHandlerMethod.getMethodArgumentValues(InvocableHandlerMethod.java:193)
        |_      Mono.zip ⇢ org.springframework.web.reactive.result.method.InvocableHandlerMethod.getMethodArgumentValues(InvocableHandlerMethod.java:200)
        |_      Mono.flatMap ⇢ org.springframework.web.reactive.result.method.InvocableHandlerMethod.invoke(InvocableHandlerMethod.java:135)
        |_      Mono.defer ⇢ org.springframework.web.reactive.result.method.annotation.RequestMappingHandlerAdapter.handle(RequestMappingHandlerAdapter.java:199)
        |_      Mono.then ⇢ org.springframework.web.reactive.result.method.annotation.RequestMappingHandlerAdapter.handle(RequestMappingHandlerAdapter.java:199)
        |_      Mono.doOnNext ⇢ org.springframework.web.reactive.result.method.annotation.RequestMappingHandlerAdapter.handle(RequestMappingHandlerAdapter.java:200)
        |_      Mono.doOnNext ⇢ org.springframework.web.reactive.result.method.annotation.RequestMappingHandlerAdapter.handle(RequestMappingHandlerAdapter.java:201)
        |_      Mono.error ⇢ org.springframework.web.reactive.result.method.annotation.RequestMappingHandlerAdapter.handleException(RequestMappingHandlerAdapter.java:234)
        |_      Mono.onErrorResume ⇢ org.springframework.web.reactive.result.method.annotation.RequestMappingHandlerAdapter.handle(RequestMappingHandlerAdapter.java:202)
        |_      Mono.flatMap ⇢ org.springframework.web.reactive.DispatcherHandler.handle(DispatcherHandler.java:151)
        |_      Mono.flatMap ⇢ org.springframework.web.reactive.DispatcherHandler.handle(DispatcherHandler.java:152)
        |_      Mono.defer ⇢ org.springframework.web.server.handler.DefaultWebFilterChain.filter(DefaultWebFilterChain.java:119)
        |_      Mono.flatMap ⇢ org.springframework.web.filter.reactive.HiddenHttpMethodFilter.filter(HiddenHttpMethodFilter.java:90)
        |_      Mono.defer ⇢ org.springframework.web.server.handler.DefaultWebFilterChain.filter(DefaultWebFilterChain.java:119)

---

This exception is masking real problem and causing a lot of confusion. I noticed that there is a lot issues that mention this exception, so this seems like a widespread problem: https://github.com/spring-projects/spring-framework/issues?q=is%3Aissue+Only+one+connection+receive

Would it be possible to present real exception in logs to make debugging easier?

Thanks!

[bclozel]

This exception happens when your application is trying to read twice the request body, and this is forbidden as this would work against backpressure support. Many things can lead to this particular symptom, so this is why you're seeing this error multiple times in our tracker. This doesn't mean the same problem is widespread.

In your case, your curl request is sending the request body with Content-Type: application/x-www-form-urlencoded; Spring Boot has an auto-configured WebFilter that parses the form request and makes it available for binding. Then the request is mapped to a controller handler that asks for the full request body with @RequestBody. This is where the problem comes from.

I'll leave this issue opened for now, in case we can get a clearer message for this particular case.

[rstoyanchev]

I think we could get a better message.

This is happening in AbstractMessageReaderArgumentResolver, so one option would be to anticipate the issue for @RequestBody arguments , in handleReadError we could check if the content-type is application/x-www-form-urlencoded and if the error message contains "only one connection", and if so extend the error message to also say "This could be because ...".

Alternatively, we could make the same check from HiddenHttpMethodFilter itself on the way out and enhance the error message.