Spring-boot: Netty unable to start (timeout)

[danielfernandez]

None of my WebFlux-based projects using Spring Boot 2.0.0.BUILD-SNAPSHOT is able to start. When executing mvn -U clean compile spring-boot:run I'm always getting:

[WARNING]
java.lang.reflect.InvocationTargetException
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:497)
    at org.springframework.boot.maven.AbstractRunMojo$LaunchRunner.run(AbstractRunMojo.java:499)
    at java.lang.Thread.run(Thread.java:745)
Caused by: org.springframework.boot.web.server.WebServerException: Unable to start Netty
    at org.springframework.boot.web.embedded.netty.NettyWebServer.start(NettyWebServer.java:65)
    at org.springframework.boot.web.reactive.context.ReactiveWebServerApplicationContext.startReactiveWebServer(ReactiveWebServerApplicationContext.java:139)
    at org.springframework.boot.web.reactive.context.ReactiveWebServerApplicationContext.finishRefresh(ReactiveWebServerApplicationContext.java:72)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:552)
    at org.springframework.boot.web.reactive.context.ReactiveWebServerApplicationContext.refresh(ReactiveWebServerApplicationContext.java:49)
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:750)
    at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:386)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:327)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1245)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1233)
    at com.example.demo.DemoApplication.main(DemoApplication.java:10)
    ... 6 more
Caused by: reactor.core.Exceptions$ReactiveException: java.util.concurrent.TimeoutException: HttpServer couldn't be started within 3000ms
    at reactor.core.Exceptions.propagate(Exceptions.java:240)
    at reactor.core.publisher.BlockingSingleSubscriber.blockingGet(BlockingSingleSubscriber.java:87)
    at reactor.core.publisher.Mono.block(Mono.java:1296)
    at reactor.ipc.netty.tcp.BlockingNettyContext.<init>(BlockingNettyContext.java:55)
    at reactor.ipc.netty.tcp.BlockingNettyContext.<init>(BlockingNettyContext.java:45)
    at reactor.ipc.netty.NettyConnector.start(NettyConnector.java:53)
    at org.springframework.boot.web.embedded.netty.NettyWebServer.start(NettyWebServer.java:59)
    ... 16 more
    Suppressed: java.lang.Exception: #block terminated with an error
        at reactor.core.publisher.BlockingSingleSubscriber.blockingGet(BlockingSingleSubscriber.java:88)
        ... 21 more
Caused by: java.util.concurrent.TimeoutException: HttpServer couldn't be started within 3000ms
    at reactor.ipc.netty.tcp.BlockingNettyContext.<init>(BlockingNettyContext.java:53)
    ... 19 more

Environment

This happens on (at least) macOS Sierra:

➜  demo mvn -version
Apache Maven 3.5.0 (ff8f5e7444045639af65f6095c62210b5713f426; 2017-04-03T21:39:06+02:00)
Maven home: /usr/local/Cellar/maven/3.5.0/libexec
Java version: 1.8.0_66, vendor: Oracle Corporation
Java home: /Library/Java/JavaVirtualMachines/jdk1.8.0_66.jdk/Contents/Home/jre
Default locale: en_US, platform encoding: UTF-8
OS name: "mac os x", version: "10.12.5", arch: "x86_64", family: "mac"

How to replicate

Simply go to http://start.spring.io, create an application with Reactive Web using Spring Boot 2.0.0.BUILD-SNAPSHOT. Try to start it and the above exception appears.

[danielfernandez]

Note: This does not happen with Spring Boot 2.0.0.M2.

[mbhave]

@danielfernandez I'm not able to reproduce this and my environment looks pretty much the same as yours. I can see that the server starts up fine: Netty started on port(s): 8080.

@bclozel do you think this might be related to the change that went in as part of #9698?

[danielfernandez]

Maybe this is normal, given the timeout of 3 seconds. In my laptop, starting Netty with Spring Boot 2.0.0.M2 takes 5 seconds:

2017-07-13 08:31:26.184  INFO 908 --- [           main] o.s.j.e.a.AnnotationMBeanExporter        : Registering beans for JMX exposure on startup
2017-07-13 08:31:31.287  INFO 908 --- [           main] o.s.b.web.embedded.netty.NettyWebServer  : Netty started on port(s): 8080

This is a 2015 MacBook Pro with an i5 2.9Ghz and 16GB RAM so, maybe that 3000ms timeout is a bit tight?

[wilkinsona]

Netty should start way faster than that on that machine. @danielfernandez I wonder if you're affected by this: https://thoeni.io/post/macos-sierra-java/

[danielfernandez]

@wilkinsona exactly, thank you very much. That was it.

2017-07-13 08:58:01.736  INFO 1237 --- [           main] o.s.j.e.a.AnnotationMBeanExporter        : Registering beans for JMX exposure on startup
2017-07-13 08:58:01.866  INFO 1237 --- [ctor-http-nio-1] r.ipc.netty.tcp.BlockingNettyContext     : Started HttpServer on /0:0:0:0:0:0:0:0:8080
2017-07-13 08:58:01.870  INFO 1237 --- [           main] o.s.b.web.embedded.netty.NettyWebServer  : Netty started on port(s): 8080

Sorry for the alarm, then. At least this ticket will serve as documentation for others having this in the future :). You can close this at your convenience.

[qintianjie]

I can reproduce this issue when in debug model.

I think it is useful to add timeout parameter from:
org.springframework.boot.web.embedded.netty.NettyWebServer.start()
to
org.springframework.boot.web.embedded.netty.NettyWebServer.start(timeout)

so than we can set the value when init BlockingNettyContext, because the default value is 45S and we can't change it till now.

@Override
public void start(**timeout**) throws WebServerException {
    if (this.nettyContext == null) {
        try {
            this.nettyContext = this.reactorServer.start(this.handlerAdapter);
            // change to 
            // this.nettyContext = this.reactorServer.start(this.handlerAdapter, timeout);
        }

[wilkinsona]

@qintianjie That's an interesting suggestion. Could you please open a separate issue so that we can make sure that it's considered?

[qintianjie]

@wilkinsona off course. I will do it now.