Exception during API request - java.net.ConnectException: connect(..) failed: Can't assign requested address

[prasannajoshi2121]

Getting following error while running Webclient requests in loop , as follows :

ClientHttpConnector httpConnector =
    new ReactorClientHttpConnector(
        HttpClient.newConnection().compress(true)));

Webclient client =  webClientBuilder
        .clientConnector(httpConnector)
        .baseUrl(baseURL)
        .build();

API calling in loop :

                    client
                    .post()
                    .uri(uri)
                    .bodyValue(rq)
                    .exchange()
                    .flatMap(
                        r -> {
                          if (!r.statusCode().is2xxSuccessful()) {
                   ...

io.netty.channel.AbstractChannel$AnnotatedConnectException: connect(..) failed: Can't assign requested address: localhost/127.0.0.1:8444
	Suppressed: reactor.core.publisher.FluxOnAssembly$OnAssemblyException: 
Error has been observed at the following site(s):
	|_ checkpoint ⇢ Request to POST http://localhost:8444/testaddress [DefaultWebClient]
Stack trace:
2020-09-11T19:46:41.688Z	[ERROR]	90-reactor-http-kqueue-8	reactor.core.publisher.MonoPeekTerminal$MonoTerminalPeekSubscriber:onError:243	na	message-processor interrupted due exception	
Caused by: java.net.ConnectException: connect(..) failed: Can't assign requested address
	at io.netty.channel.unix.Errors.throwConnectException(Errors.java:124)
	at io.netty.channel.unix.Socket.connect(Socket.java:231)
	at io.netty.channel.kqueue.AbstractKQueueChannel.doConnect0(AbstractKQueueChannel.java:717)
	at io.netty.channel.kqueue.AbstractKQueueChannel.doConnect(AbstractKQueueChannel.java:702)
	at io.netty.channel.kqueue.AbstractKQueueChannel$AbstractKQueueUnsafe.connect(AbstractKQueueChannel.java:548)
	at io.netty.channel.DefaultChannelPipeline$HeadContext.connect(DefaultChannelPipeline.java:1342)
	at io.netty.channel.AbstractChannelHandlerContext.invokeConnect(AbstractChannelHandlerContext.java:548)
	at io.netty.channel.AbstractChannelHandlerContext.connect(AbstractChannelHandlerContext.java:533)
	at io.netty.channel.CombinedChannelDuplexHandler$DelegatingChannelHandlerContext.connect(CombinedChannelDuplexHandler.java:495)
	at io.netty.channel.ChannelOutboundHandlerAdapter.connect(ChannelOutboundHandlerAdapter.java:51)
	at io.netty.channel.CombinedChannelDuplexHandler.connect(CombinedChannelDuplexHandler.java:296)
	at io.netty.channel.AbstractChannelHandlerContext.invokeConnect(AbstractChannelHandlerContext.java:548)
	at io.netty.channel.AbstractChannelHandlerContext.connect(AbstractChannelHandlerContext.java:533)
	at io.netty.channel.AbstractChannelHandlerContext.connect(AbstractChannelHandlerContext.java:517)
	at io.netty.channel.DefaultChannelPipeline.connect(DefaultChannelPipeline.java:978)
	at io.netty.channel.AbstractChannel.connect(AbstractChannel.java:253)
	at io.netty.bootstrap.Bootstrap$3.run(Bootstrap.java:250)
	at io.netty.util.concurrent.AbstractEventExecutor.safeExecute(AbstractEventExecutor.java:164)
	at io.netty.util.concurrent.SingleThreadEventExecutor.runAllTasks(SingleThreadEventExecutor.java:472)
	at io.netty.channel.kqueue.KQueueEventLoop.run(KQueueEventLoop.java:293)
	at io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:989)
	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)

while hitting server from postman , getting expected response.

spring boot version : <spring.boot.version>2.3.3.RELEASE</spring.boot.version>
reactor core: 3.3.9-RELEASE
reactor-netty : 0.9.11.RELEASE

[philwebb]

I'm a little confused about the "Can't assign requested address" since this is a client-side call. I suspect something is misconfigured in your application. Could you please provide a minimal reproducible example either as a GitHub project or as an attached zip file. We'll need something that we can download and run ourselves.

[prasannajoshi2121]

@philwebb please find minimal reproducible example repo

Client App - https://github.com/prasannajoshi2121/spring-test-client.git
Server App - https://github.com/prasannajoshi2121/test-vertx-server.git

Please update this file spring-test-client/first-project/src/main/java/com/first/firstproject/FirstProjectApplication.java like below :
//ClientHttpConnector httpConnector = new ReactorClientHttpConnector(HttpClient.create().compress(true)); ClientHttpConnector httpConnector = new ReactorClientHttpConnector(HttpClient.newConnection());

inside Client App repo , src/main/resource directory please find Httprequest.JMX script.

(Path - spring-test-client/first-project/src/main/resources/HTTP Request.jmx)

Please run JMX script to reproduce issue once Client and server started.

[philwebb]

Calling subscribe() from your @Controller method is unusual and likely to lead to the problems you're seeing. It can be justified if you wanted to kick off some asynchronous processing that is detached from the completion of request handling. However if that asynchronous handling has higher delays, that means you can end up with more and more requests coming in, and more of those asynchronous tasks piling up. It seems like that's happening with your sample. It's more typical to return a Mono or Flux from the controller.

One other thing to point out is that you should not use exchange() unless it is for more advanced scenarios because you can easily omit to consume response content in cases errors (4xx or 5xx response) or a cancellation (e.g. the connection was closed by the remote end or the HTTP client) and if you don't handle those you can get a memory and/or connection leak. This is why Spring Framework now plans to deprecate exchange() (see spring-projects/spring-framework#25751).

All things considered, this doesn't look like a bug in Spring Boot or WebFlux, but it feels like a question that would be better suited to Stack Overflow. We prefer to use GitHub issues only for bugs and enhancements.

(Thanks to Rossen Stoyanchev from the WebFlux team who helped with this answer)

[rdp]

Was this ever posted to stackoverflow? If so link possible? Thanks.