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WebClient logs "IllegalStateException: Only one connection receive subscriber allowed" when multiple requests made within Kotlin coroutine and response status is an error
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Kotlin version: 1.5.30 Spring Boot version: 2.5.4 and 2.6.1 Spring Framework version: 5.3.9
When making multiple WebClient requests within a Kotlin coroutine, if one of them fails with a 4xx or 5xx status, there are two errors logged... an expected WebClientResponseException and an unexpected IllegalStateException: Only one connection receive subscriber allowed from Reactor. A unit test to reproduce the behavior along with the full stack trace are posted below.
There may be other ways to reproduce this error, but in the case below, it only happens if the request is expecting a body and the 4xx response does not contain one. Also, if you comment out the /path1 request, the /path2 request fails normally without the additional Reactor exception, even if the 4xx response doesn't contain a body.
Unit test (spring-cloud-contract-wiremock is used to mock the server):
@SpringBootTest
@AutoConfigureWireMock(port = 8089)
class WebClientTest {
private lateinit var webClient: WebClient
@BeforeEach
fun setup() {
webClient = WebClient.builder().baseUrl("http://localhost:8089").build()
stubFor(
get(urlPathEqualTo("/path1")).willReturn(
aResponse().withStatus(200)
.withHeader("Content-Type", "application/json")
.withBody("""{"data":""}""")
)
)
stubFor(
get(urlPathEqualTo("/path2")).willReturn(
aResponse().withStatus(400)
)
)
}
@Test
fun test(): Unit = runBlocking {
val result1 = async(Dispatchers.IO) {
webClient.get().uri("/path1").retrieve().awaitBody<Response>()
}
val result2 = async(Dispatchers.IO) {
webClient.get().uri("/path2").retrieve().awaitBody<Response>()
}
Pair(result1.await(), result2.await())
}
}
data class Response(val data: String)
Stack trace:
2021-12-09 10:30:32.618 ERROR 55926 --- [ctor-http-nio-4] reactor.core.publisher.Operators : Operator called default onErrorDropped
java.lang.IllegalStateException: Only one connection receive subscriber allowed.
at reactor.netty.channel.FluxReceive.startReceiver(FluxReceive.java:182)
at reactor.netty.channel.FluxReceive.subscribe(FluxReceive.java:143)
at reactor.core.publisher.InternalFluxOperator.subscribe(InternalFluxOperator.java:62)
at reactor.netty.ByteBufFlux.subscribe(ByteBufFlux.java:339)
at reactor.core.publisher.Mono.subscribe(Mono.java:4338)
at reactor.core.publisher.FluxOnErrorResume$ResumeSubscriber.onError(FluxOnErrorResume.java:103)
at reactor.core.publisher.FluxOnAssembly$OnAssemblySubscriber.onError(FluxOnAssembly.java:393)
at reactor.core.publisher.MonoFlatMap$FlatMapMain.onError(MonoFlatMap.java:172)
at reactor.core.publisher.FluxContextWrite$ContextWriteSubscriber.onError(FluxContextWrite.java:121)
at reactor.core.publisher.FluxMapFuseable$MapFuseableConditionalSubscriber.onError(FluxMapFuseable.java:334)
at reactor.core.publisher.FluxFilterFuseable$FilterFuseableConditionalSubscriber.onError(FluxFilterFuseable.java:382)
at reactor.core.publisher.MonoCollect$CollectSubscriber.onError(MonoCollect.java:144)
at reactor.core.publisher.FluxMap$MapSubscriber.onError(FluxMap.java:132)
at reactor.core.publisher.Operators.error(Operators.java:198)
at reactor.core.publisher.FluxPeek$PeekSubscriber.onSubscribe(FluxPeek.java:165)
at reactor.core.publisher.FluxMap$MapSubscriber.onSubscribe(FluxMap.java:92)
at reactor.netty.channel.FluxReceive.startReceiver(FluxReceive.java:167)
at reactor.netty.channel.FluxReceive.subscribe(FluxReceive.java:143)
at reactor.core.publisher.InternalFluxOperator.subscribe(InternalFluxOperator.java:62)
at reactor.netty.ByteBufFlux.subscribe(ByteBufFlux.java:339)
at reactor.core.publisher.InternalMonoOperator.subscribe(InternalMonoOperator.java:64)
at reactor.core.publisher.MonoFlatMap$FlatMapMain.onNext(MonoFlatMap.java:157)
at reactor.core.publisher.FluxSwitchIfEmpty$SwitchIfEmptySubscriber.onNext(FluxSwitchIfEmpty.java:74)
at reactor.core.publisher.FluxOnAssembly$OnAssemblySubscriber.onNext(FluxOnAssembly.java:388)
at reactor.core.publisher.FluxMap$MapSubscriber.onNext(FluxMap.java:120)
at reactor.core.publisher.FluxOnErrorResume$ResumeSubscriber.onNext(FluxOnErrorResume.java:79)
at reactor.core.publisher.FluxPeek$PeekSubscriber.onNext(FluxPeek.java:200)
at reactor.core.publisher.FluxPeek$PeekSubscriber.onNext(FluxPeek.java:200)
at reactor.core.publisher.FluxPeek$PeekSubscriber.onNext(FluxPeek.java:200)
at reactor.core.publisher.MonoNext$NextSubscriber.onNext(MonoNext.java:82)
at reactor.core.publisher.Operators$ScalarSubscription.request(Operators.java:2398)
at reactor.core.publisher.MonoFlatMapMany$FlatMapManyMain.onSubscribeInner(MonoFlatMapMany.java:150)
at reactor.core.publisher.MonoFlatMapMany$FlatMapManyMain.onNext(MonoFlatMapMany.java:189)
at reactor.core.publisher.SerializedSubscriber.onNext(SerializedSubscriber.java:99)
at reactor.core.publisher.FluxRetryWhen$RetryWhenMainSubscriber.onNext(FluxRetryWhen.java:174)
at reactor.core.publisher.MonoCreate$DefaultMonoSink.success(MonoCreate.java:160)
at reactor.netty.http.client.HttpClientConnect$HttpIOHandlerObserver.onStateChange(HttpClientConnect.java:414)
at reactor.netty.ReactorNetty$CompositeConnectionObserver.onStateChange(ReactorNetty.java:654)
at reactor.netty.resources.DefaultPooledConnectionProvider$DisposableAcquire.onStateChange(DefaultPooledConnectionProvider.java:201)
at reactor.netty.resources.DefaultPooledConnectionProvider$PooledConnection.onStateChange(DefaultPooledConnectionProvider.java:457)
at reactor.netty.http.client.HttpClientOperations.onInboundNext(HttpClientOperations.java:628)
at reactor.netty.channel.ChannelOperationsHandler.channelRead(ChannelOperationsHandler.java:93)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365)
at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:357)
at io.netty.handler.codec.MessageToMessageDecoder.channelRead(MessageToMessageDecoder.java:103)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365)
at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:357)
at io.netty.channel.CombinedChannelDuplexHandler$DelegatingChannelHandlerContext.fireChannelRead(CombinedChannelDuplexHandler.java:436)
at io.netty.handler.codec.ByteToMessageDecoder.fireChannelRead(ByteToMessageDecoder.java:324)
at io.netty.handler.codec.ByteToMessageDecoder.fireChannelRead(ByteToMessageDecoder.java:311)
at io.netty.handler.codec.ByteToMessageDecoder.callDecode(ByteToMessageDecoder.java:432)
at io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:276)
at io.netty.channel.CombinedChannelDuplexHandler.channelRead(CombinedChannelDuplexHandler.java:251)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365)
at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:357)
at io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1410)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365)
at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:919)
at io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:166)
at io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:719)
at io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:655)
at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:581)
at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:493)
at io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:986)
at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74)
at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30)
at java.lang.Thread.run(Thread.java:748)
org.springframework.web.reactive.function.client.WebClientResponseException$BadRequest: 400 Bad Request from GET http://localhost:8089/path2
at org.springframework.web.reactive.function.client.WebClientResponseException.create(WebClientResponseException.java:196)
Suppressed: reactor.core.publisher.FluxOnAssembly$OnAssemblyException:
Error has been observed at the following site(s):
|_ checkpoint ⇢ 400 from GET http://localhost:8089/path2 [DefaultWebClient]
Stack trace:
at org.springframework.web.reactive.function.client.WebClientResponseException.create(WebClientResponseException.java:196)
at org.springframework.web.reactive.function.client.DefaultClientResponse.lambda$createException$1(DefaultClientResponse.java:213)
at reactor.core.publisher.FluxMap$MapSubscriber.onNext(FluxMap.java:106)
at reactor.core.publisher.FluxOnErrorResume$ResumeSubscriber.onNext(FluxOnErrorResume.java:79)
at reactor.core.publisher.Operators$MonoSubscriber.complete(Operators.java:1816)
at reactor.core.publisher.FluxDefaultIfEmpty$DefaultIfEmptySubscriber.onComplete(FluxDefaultIfEmpty.java:109)
at reactor.core.publisher.FluxMapFuseable$MapFuseableSubscriber.onComplete(FluxMapFuseable.java:150)
at reactor.core.publisher.FluxContextWrite$ContextWriteSubscriber.onComplete(FluxContextWrite.java:126)
at reactor.core.publisher.FluxMapFuseable$MapFuseableConditionalSubscriber.onComplete(FluxMapFuseable.java:344)
at reactor.core.publisher.FluxFilterFuseable$FilterFuseableConditionalSubscriber.onComplete(FluxFilterFuseable.java:391)
at reactor.core.publisher.Operators$MonoSubscriber.complete(Operators.java:1817)
at reactor.core.publisher.MonoCollect$CollectSubscriber.onComplete(MonoCollect.java:159)
at reactor.core.publisher.FluxMap$MapSubscriber.onComplete(FluxMap.java:142)
at reactor.core.publisher.FluxPeek$PeekSubscriber.onComplete(FluxPeek.java:260)
at reactor.core.publisher.FluxMap$MapSubscriber.onComplete(FluxMap.java:142)
at reactor.netty.channel.FluxReceive.onInboundComplete(FluxReceive.java:400)
at reactor.netty.channel.ChannelOperations.onInboundComplete(ChannelOperations.java:419)
at reactor.netty.channel.ChannelOperations.terminate(ChannelOperations.java:473)
at reactor.netty.http.client.HttpClientOperations.onInboundNext(HttpClientOperations.java:684)
at reactor.netty.channel.ChannelOperationsHandler.channelRead(ChannelOperationsHandler.java:93)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365)
at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:357)
at io.netty.handler.codec.MessageToMessageDecoder.channelRead(MessageToMessageDecoder.java:103)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365)
at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:357)
at io.netty.channel.CombinedChannelDuplexHandler$DelegatingChannelHandlerContext.fireChannelRead(CombinedChannelDuplexHandler.java:436)
at io.netty.handler.codec.ByteToMessageDecoder.fireChannelRead(ByteToMessageDecoder.java:324)
at io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:296)
at io.netty.channel.CombinedChannelDuplexHandler.channelRead(CombinedChannelDuplexHandler.java:251)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365)
at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:357)
at io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1410)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365)
at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:919)
at io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:166)
at io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:719)
at io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:655)
at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:581)
at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:493)
at io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:986)
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 similar to https://github.com/spring-projects/spring-framework/issues/26699
