java - Spring RestTemplate & AsyncRestTemplate with Netty4 hangs forever -

very simple setup:

pom.xml

<?xml version="1.0" encoding="utf-8"?> <project xmlns="http://maven.apache.org/pom/4.0.0" xmlns:xsi="http://www.w3.org/2001/xmlschema-instance"     xsi:schemalocation="http://maven.apache.org/pom/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">     <modelversion>4.0.0</modelversion>      <groupid>com.example</groupid>     <artifactid>demo-rest-client</artifactid>     <version>0.0.1-snapshot</version>     <packaging>jar</packaging>      <name>demo-rest-client</name>     <description>demo project spring boot</description>      <parent>         <groupid>org.springframework.boot</groupid>         <artifactid>spring-boot-starter-parent</artifactid>         <version>1.4.1.release</version>         <relativepath/> <!-- lookup parent repository -->     </parent>      <properties>         <project.build.sourceencoding>utf-8</project.build.sourceencoding>         <project.reporting.outputencoding>utf-8</project.reporting.outputencoding>         <java.version>1.8</java.version>     </properties>      <dependencies>         <dependency>             <groupid>org.springframework.boot</groupid>             <artifactid>spring-boot-starter-web</artifactid>         </dependency>         <dependency>             <groupid>io.netty</groupid>             <artifactid>netty-all</artifactid>             <version>4.1.5.final</version>         </dependency>         <dependency>             <groupid>io.netty</groupid>             <artifactid>netty-buffer</artifactid>             <version>4.1.5.final</version>         </dependency>         <dependency>             <groupid>com.squareup.okhttp3</groupid>             <artifactid>okhttp</artifactid>             <version>3.4.1</version>         </dependency>         <dependency>             <groupid>io.github.openfeign</groupid>             <artifactid>feign-core</artifactid>             <version>9.3.1</version>         </dependency>         <dependency>             <groupid>io.github.openfeign</groupid>             <artifactid>feign-hystrix</artifactid>             <version>9.3.1</version>         </dependency>          <dependency>             <groupid>org.springframework.boot</groupid>             <artifactid>spring-boot-starter-test</artifactid>             <scope>test</scope>         </dependency>     </dependencies>      <build>         <plugins>             <plugin>                 <groupid>org.springframework.boot</groupid>                 <artifactid>spring-boot-maven-plugin</artifactid>             </plugin>         </plugins>     </build>  </project> 

and test case demonstrate different usages of asyncresttemplate:

sampletests.java

package com.example;  import com.netflix.hystrix.hystrixcommand; import com.netflix.hystrix.hystrixcommandproperties; import feign.requestline; import feign.hystrix.hystrixfeign; import feign.hystrix.setterfactory; import org.junit.test; import org.springframework.http.responseentity; import org.springframework.http.client.netty4clienthttprequestfactory; import org.springframework.http.client.okhttp3clienthttprequestfactory; import org.springframework.util.concurrent.listenablefuture; import org.springframework.web.client.asyncresttemplate; import org.springframework.web.client.resttemplate;  public class sampletests {      private static final string url = "https://api.github.com/users/octocat";     private static final int default_sleep_millis = 20;     private static final int default_timeout = 10000;      @test(timeout = default_timeout)     public void syncrestnetty() throws exception {         resttemplate resttemplate = new resttemplate(new netty4clienthttprequestfactory());         responseentity<string> response = resttemplate.getforentity(url, string.class);         system.out.println("response = " + response);     }      @test(timeout = default_timeout)     public void asyncrestnetty() throws exception {         asyncresttemplate resttemplate = new asyncresttemplate(new netty4clienthttprequestfactory());         listenablefuture<responseentity<string>> listenablefuture = resttemplate.getforentity(url, string.class);         listenablefuture.addcallback(result -> system.out.println("result = " + result), throwable::printstacktrace);         while (!listenablefuture.isdone()) {             thread.sleep(default_sleep_millis);         }         system.out.println("the end");     }      @test     public void asyncrestokhttp() throws exception {         asyncresttemplate resttemplate = new asyncresttemplate(new okhttp3clienthttprequestfactory());         listenablefuture<responseentity<string>> listenablefuture = resttemplate.getforentity(url, string.class);         listenablefuture.addcallback(result -> system.out.println("result = " + result), throwable::printstacktrace);         while (!listenablefuture.isdone()) {             thread.sleep(default_sleep_millis);         }         system.out.println("the end");     }      @test     public void asyncresthystrixfeign() throws exception {         github github = hystrixfeign.builder()                 .setterfactory((target, method) -> new setterfactory.default().create(target, method).andcommandpropertiesdefaults(hystrixcommandproperties.defaultsetter().withexecutiontimeoutinmilliseconds(10000)))                 .target(github.class, "https://api.github.com");         hystrixcommand<string> command = github.octocatasync();         command.toobservable().subscribe(result -> system.out.println("result = " + result), throwable::printstacktrace);         while (!command.isexecutioncomplete()) {             thread.sleep(default_sleep_millis);         }         system.out.println("command.getexecutiontimeinmilliseconds() = " + command.getexecutiontimeinmilliseconds());         system.out.println("the end");     }      interface github {         @requestline("get /users/octocat")         hystrixcommand<string> octocatasync();     } } 

when trying run tests use netty hang forever. (to see please remove junit timeout constraint). if run exact same code other clients works expected.

i have tried different versions of spring boot , netty did not succeed. , logs looks ok.

what missing here?

edit: opened ticket https://jira.spring.io/browse/spr-14744 suggested on spring gitter

edit-2: answer brian clozel helped me find issue related netty not realizing server sent empty response (a particular case github api , plain http) marking accepted.

can try configure request factory netty sslcontext?

netty4clienthttprequestfactory nettyfactory = new netty4clienthttprequestfactory(); nettyfactory.setsslcontext(sslcontextbuilder.forclient().build()); asyncresttemplate resttemplate = new asyncresttemplate(nettyfactory); 

without context, client trying send plaintext requests https endpoint; in case, you're getting http 400 response.

in example code, throwable should instance of httpclienterrorexception, , information logging response status or body exception.getresponsebodyasstring().