HttpClient blocked after a failed request, error "unexpected message type: DefaultHttpRequest"

[fayndee]

Version:
spring-boot-starter-web-reactive:0.1.0.BUILD-SNAPSHOT => reactor-netty-0.6.0.BUILD-20161219.135933-150

We used spring-web-reactive in our application since a while and it worked fine. Today, we got exception in our test client and the process is blocked somehow due to this error:

2016-12-19 18:49:24,359 [reactor-http-nio-1] ERROR reactor.ipc.netty.channel.ChannelOperations - [HttpClient] Error processing connection. Requesting close the channel
io.netty.handler.codec.EncoderException: java.lang.IllegalStateException: unexpected message type: DefaultHttpRequest
	at io.netty.handler.codec.MessageToMessageEncoder.write(MessageToMessageEncoder.java:106)
	at io.netty.channel.AbstractChannelHandlerContext.invokeWrite0(AbstractChannelHandlerContext.java:749)
	at io.netty.channel.AbstractChannelHandlerContext.invokeWriteAndFlush(AbstractChannelHandlerContext.java:812)
	at io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:825)
	at io.netty.channel.AbstractChannelHandlerContext.writeAndFlush(AbstractChannelHandlerContext.java:805)
	at reactor.ipc.netty.channel.ChannelOperationsHandler.doWrite(ChannelOperationsHandler.java:267)
	at reactor.ipc.netty.channel.ChannelOperationsHandler.drain(ChannelOperationsHandler.java:368)
	at reactor.ipc.netty.channel.ChannelOperationsHandler.flush(ChannelOperationsHandler.java:150)
	at io.netty.channel.AbstractChannelHandlerContext.invokeFlush0(AbstractChannelHandlerContext.java:787)
	at io.netty.channel.AbstractChannelHandlerContext.invokeWriteAndFlush(AbstractChannelHandlerContext.java:813)
	at io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:825)
	at io.netty.channel.AbstractChannelHandlerContext.writeAndFlush(AbstractChannelHandlerContext.java:805)
	at io.netty.channel.AbstractChannelHandlerContext.writeAndFlush(AbstractChannelHandlerContext.java:842)
	at io.netty.channel.DefaultChannelPipeline.writeAndFlush(DefaultChannelPipeline.java:1032)
	at io.netty.channel.AbstractChannel.writeAndFlush(AbstractChannel.java:296)
	at reactor.ipc.netty.http.HttpOperations.lambda$sendHeaders$0(HttpOperations.java:98)
	at reactor.ipc.netty.FutureMono$DeferredFutureMono.subscribe(FutureMono.java:114)
	at reactor.core.publisher.FluxConcatIterable$ConcatIterableSubscriber.onComplete(FluxConcatIterable.java:152)
	at reactor.core.publisher.FluxConcatIterable.subscribe(FluxConcatIterable.java:69)
	at reactor.core.publisher.MonoNext.subscribe(MonoNext.java:41)
	at reactor.ipc.netty.channel.ChannelOperations.applyHandler(ChannelOperations.java:421)
	at reactor.ipc.netty.http.client.HttpClientOperations.onChannelActive(HttpClientOperations.java:452)
	at reactor.ipc.netty.channel.PooledClientContextHandler.connectOrAcquire(PooledClientContextHandler.java:171)
	at reactor.ipc.netty.channel.PooledClientContextHandler.lambda$operationComplete$0(PooledClientContextHandler.java:118)
	at io.netty.util.concurrent.AbstractEventExecutor.safeExecute(AbstractEventExecutor.java:163)
	at io.netty.util.concurrent.SingleThreadEventExecutor.runAllTasks(SingleThreadEventExecutor.java:418)
	at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:454)
	at io.netty.util.concurrent.SingleThreadEventExecutor$5.run(SingleThreadEventExecutor.java:873)
	at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.IllegalStateException: unexpected message type: DefaultHttpRequest
	at io.netty.handler.codec.http.HttpObjectEncoder.encode(HttpObjectEncoder.java:69)
	at io.netty.handler.codec.MessageToMessageEncoder.write(MessageToMessageEncoder.java:88)

After this error, the process is hanging forever. To reproduce this, one could setup a spring boot project using the version mentioned above and with the follow classes:

Application.java

@SpringBootApplication
public class Application {
    public static void main(String[] args) {
        new SpringApplication().run(args);
    }
}

AnyController.java

@Controller
@RequestMapping("/any")
public class AnyController {
    @RequestMapping(value = "/thing", method = RequestMethod.HEAD)
    public Mono<ResponseEntity<Void>> testAny() {
        return Mono.just(ResponseEntity.notFound().build());
    }
}

AnyControllerTest.java

@RunWith(SpringRunner.class)
@SpringBootTest(classes = Application.class, webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
public class AnyControllerTest {
    @LocalServerPort
    int port;
    String url = "http://localhost:{port}/any/thing";
    WebClient webClient = WebClient.create(new ReactorClientHttpConnector());
    @Test
    public void aTest() {
        Mono<ClientResponse> response = webClient.exchange(ClientRequest.HEAD(url, port).build());
        assert response.block().statusCode() == HttpStatus.NOT_FOUND;
    }
    @Test
    public void anotherTest() {
        Mono<ClientResponse> response = webClient.exchange(ClientRequest.HEAD(url, port).build());
        assert response.block().statusCode() == HttpStatus.NOT_FOUND;
    }
}

When one runs the test, the first test case will succeed without any problem, however the second one will be simply blocked and hangs forever....

[fayndee]

FYI, when I switch back to reactor-netty-0.6.0.BUILD-20161216.012745-138, the problem disappears.

[smaldini]

Should be fixed in latest snapshot we refined some of this before 0.6.0.RELEASE which should be out today