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关于java:dubbogo-白话文-从零搭建-dubbogo-和-dubbo-的简单用例

jiezi

作者 | 铁城  dubbo-go 社区 committer
起源 | 阿里巴巴云原生公众号

本文将手把手教你应用 dubbogo 调用 dubbogo 或 dubbo 提供的服务提供方。

前言

本文基于 dubbogo 1.5.4 版本。

最近开始参加 dubbogo 的一些开发测试，之前都是间接拿 samples 的例子验证性能，而这次为了复现一个性能问题，打算从零开始搭建一个 dubbo-go 和 dubbo 调用的工程，踩到了一些新人应用 dubbogo 的坑，把这个过程记录下供大家参考。

通过本文你能够理解到：

  • 如何惯例配置 dubbogo 生产方去调用 dubbo 和 dubbogo 服务提供方。
  • 通过一个理论的 BUG 介绍解决问题的思路。

解决问题

1. 筹备 dubbo 服务提供者

1）根本定义

定义 DemoService 接口：

public interface DemoService {String sayHello(String name);

    String sayHello(User user);

    String sayHello(User user, String name);

}

定义 User 对象：

public class User implements Serializable {

    private String name;

    private int age;

    ......
}

2）启动 dubbo 服务提供者

用的 dubbo 官网示例代码：

public static void main(String[] args) throws IOException {
    // 服务实现
    DemoService demoService = new DemoServiceImpl();

    // 以后利用配置
    ApplicationConfig application = new ApplicationConfig();
    application.setName("demoProvider");

    // 连贯注册核心配置
    RegistryConfig registry = new RegistryConfig();
    registry.setAddress("127.0.0.1:2181");
    registry.setProtocol("zookeeper");
    registry.setUsername("");
    registry.setPassword("");

    // 服务提供者协定配置
    ProtocolConfig protocol = new ProtocolConfig();
    protocol.setName("dubbo");
    protocol.setPort(12345);
    protocol.setThreads(200);

    // 留神：ServiceConfig 为重对象，外部封装了与注册核心的连贯，以及开启服务端口

    // 服务提供者裸露服务配置
    ServiceConfig<DemoService> service = new ServiceConfig<>(); // 此实例很重，封装了与注册核心的连贯，请自行缓存，否则可能造成内存和连贯透露
    service.setApplication(application);
    service.setRegistry(registry); // 多个注册核心能够用 setRegistries()
    service.setProtocol(protocol); // 多个协定能够用 setProtocols()
    service.setInterface(DemoService.class);
    service.setRef(demoService);
    service.setVersion("1.0.0");
    service.setGroup("tc");
    service.setTimeout(60 * 1000);

    // 裸露及注册服务
    service.export();

    System.in.read();}

查看 zookeeper 看是否注册胜利：

$ls /dubbo/com.funnycode.DemoService/providers
[dubbo%3A%2F%2F127.0.0.1%3A12345%2Fcom.funnycode.DemoService%3Fanyhost%3Dtrue%26application%3DdemoProvider%26deprecated%3Dfalse%26dubbo%3D2.0.2%26dynamic%3Dtrue%26generic%3Dfalse%26group%3Dtc%26interface%3Dcom.funnycode.DemoService%26methods%3DsayHello%26pid%3D18167%26release%3D2.7.7%26revision%3D1.0.0%26side%3Dprovider%26threads%3D200%26timestamp%3D1606896020691%26version%3D1.0.0]

如上的输入示意服务提供方曾经启动。

2. 筹备 dubbogo 服务消费者

1）根本定义

定义 User 对象：

type User struct {
    Name string
    Age  int
}

func (User) JavaClassName() string {return "com.funnycode.User"}

定义 DemoProvider 接口：

type DemoProvider struct {SayHello  func(ctx context.Context, name string) (string, error)            `dubbo:"sayHello"`
    SayHello2 func(ctx context.Context, user User) (string, error)              `dubbo:"sayHello"`
    SayHello3 func(ctx context.Context, user User, name string) (string, error) `dubbo:"sayHello"`
}

func (p *DemoProvider) Reference() string {return "DemoProvider"}

2）启动 dubbogo 消费者 

func main() {config.Load()
    gxlog.CInfo("\n\n\nstart to test dubbo")

    res, err := demoProvider.SayHello(context.TODO(), "tc")
    if err != nil {panic(err)
    }

    gxlog.CInfo("response result: %v\n", res)

    user := User{
        Name: "tc",
        Age:  18,
    }

    res, err = demoProvider.SayHello2(context.TODO(), user)
    if err != nil {panic(err)
    }

    gxlog.CInfo("response result: %v\n", res)

    res, err = demoProvider.SayHello3(context.TODO(), user, "tc")
    if err != nil {panic(err)
    }

    gxlog.CInfo("response result: %v\n", res)

    initSignal()}

3. 申请后果剖析

1）间接调用

确认问题的存在。

第一个接口的参数是字符串，能够失常返回 [2020-12-03/18:59:12 main.main: client.go: 29] response result: Hello tc。

第二、三两个接口存在 User 对象，无奈调用胜利。错误信息如下：

2020-12-02T17:10:47.739+0800    INFO    getty/listener.go:87    session{session session-closed, Read Bytes: 924, Write Bytes: 199, Read Pkgs: 0, Write Pkgs: 1} got error{java exception:Fail to decode request due to: java.lang.IllegalArgumentException: Service not found:com.funnycode.DemoService, sayHello
        at org.apache.dubbo.rpc.protocol.dubbo.DecodeableRpcInvocation.decode(DecodeableRpcInvocation.java:134)
        at org.apache.dubbo.rpc.protocol.dubbo.DecodeableRpcInvocation.decode(DecodeableRpcInvocation.java:80)
        at org.apache.dubbo.remoting.transport.DecodeHandler.decode(DecodeHandler.java:57)
        at org.apache.dubbo.remoting.transport.DecodeHandler.received(DecodeHandler.java:44)
        at org.apache.dubbo.remoting.transport.dispatcher.ChannelEventRunnable.run(ChannelEventRunnable.java:57)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
        at java.lang.Thread.run(Thread.java:748)
}, will be closed.

谬误正如 issue 中形容的截然不同，因为错误信息返回到了生产端，能够看到 Java 那边的谬误堆栈信息，所以间接去看 DecodeableRpcInvocation.decode#134。

2）断点查看

代码如下：

// 反序列化
public class DecodeableRpcInvocation extends RpcInvocation implements Codec, Decodeable {public Object decode(Channel channel, InputStream input) throws IOException {
      ......
      if (serviceDescriptor != null) {
          // 办法形容外面依据办法名查找
          MethodDescriptor methodDescriptor = serviceDescriptor.getMethod(getMethodName(), desc);
          if (methodDescriptor != null) {pts = methodDescriptor.getParameterClasses();
              this.setReturnTypes(methodDescriptor.getReturnTypes());
          }
      }
      // 示意没有找到办法        
      if (pts == DubboCodec.EMPTY_CLASS_ARRAY) {if (!RpcUtils.isGenericCall(path, getMethodName()) && !RpcUtils.isEcho(path, getMethodName())) {throw new IllegalArgumentException("Service not found:" + path + "," + getMethodName());
          }
          pts = ReflectUtils.desc2classArray(desc);
      }
      ......
    }
}
  • 查看 MethodDescriptor，即找办法是否存在，存在的话就会设置好 ParameterClasses。
  • 如果下面没找到，pts == DubboCodec.EMPTY_CLASS_ARRAY 就会满足条件，进而判断是否是泛化调用或者是 echo 调用，如果都不是则报服务找不到办法谬误。
  • desc 是 Ljava/lang/Object，很显著并没有参数是 Object 的办法，所以必然是会报错的。

补充阐明：办法查问。
**
代码如下:

public MethodDescriptor getMethod(String methodName, String params) {Map<String, MethodDescriptor> methods = descToMethods.get(methodName);
    if (CollectionUtils.isNotEmptyMap(methods)) {return methods.get(params);
    }
    return null;
}

长处 ：比之前的版本加了办法的元信息缓存起来，不应用反射能够提高效率，能够了解用空间换工夫。

4. 解决问题

因为间接撸代码并 hold 不住，所以通过比拟来查看问题所在。

1）启动 dubbo 服务消费者

通过 api 模式启动，参考官网例子。启动这个是为了查看 Java 版本的传输内容。

public static void main(String[] args) throws InterruptedException {
    // 以后利用配置
    ApplicationConfig application = new ApplicationConfig();
    application.setName("demoProvider2");

    // 连贯注册核心配置
    RegistryConfig registry = new RegistryConfig();
    registry.setAddress("127.0.0.1:2181");
    registry.setProtocol("zookeeper");
    registry.setUsername("");
    registry.setPassword("");
    // 留神：ReferenceConfig 为重对象，外部封装了与注册核心的连贯，以及与服务提供方的连贯

    // 援用近程服务
    ReferenceConfig<DemoService> reference
        = new ReferenceConfig<>(); // 此实例很重，封装了与注册核心的连贯以及与提供者的连贯，请自行缓存，否则可能造成内存和连贯透露
    reference.setApplication(application);
    reference.setRegistry(registry); // 多个注册核心能够用 setRegistries()
    reference.setInterface(DemoService.class);
    reference.setVersion("1.0.0");
    reference.setGroup("tc");
    reference.setCheck(true);
    reference.setTimeout(1000 * 60);

    // 和本地 bean 一样应用 xxxService
    DemoService demoService = reference.get(); // 留神：此代理对象外部封装了所有通信细节，对象较重，请缓存复用
    System.out.println(demoService.sayHello(new User("tc", 18)));

    TimeUnit.MINUTES.sleep(10);
}

desc 肉眼可见的是 Lcom/funnycode/User，这个就是正确的对象了。

2）查找 dubbogo 为什么不对

代码地位：
protocol/dubbo/impl/hessian.go:120#marshalRequest

代码实现：

func marshalRequest(encoder *hessian.Encoder, p DubboPackage) ([]byte, error) {
    service := p.Service
    request := EnsureRequestPayload(p.Body)
    encoder.Encode(DEFAULT_DUBBO_PROTOCOL_VERSION)
    encoder.Encode(service.Path)
    encoder.Encode(service.Version)
    encoder.Encode(service.Method)

    args, ok := request.Params.([]interface{})

    if !ok {logger.Infof("request args are: %+v", request.Params)
        return nil, perrors.Errorf("@params is not of type: []interface{}")
    }
    types, err := getArgsTypeList(args)
    if err != nil {return nil, perrors.Wrapf(err, "PackRequest(args:%+v)", args)
    }
    encoder.Encode(types)
    for _, v := range args {encoder.Encode(v)
    }

    ......
}

断点能够发现，types 返回的时候就曾经是 Object 了，没有返回 User，那么持续跟进去查看代码。

  • protocol/dubbo/impl/hessian.go:394#getArgsTypeList
  • protocol/dubbo/impl/hessian.go:418#getArgType
func getArgType(v interface{}) string {
  // 常见的类型解决

  ......

  default:
    t := reflect.TypeOf(v)
    if reflect.Ptr == t.Kind() {t = reflect.TypeOf(reflect.ValueOf(v).Elem())
    }
    switch t.Kind() {
    case reflect.Struct:
      return "java.lang.Object"
    }
    ......
}

很显著当发现是 reflect.Struct 的时候就返回了 java.lang.Object，所以参数就变成了 Object，那么因为 Java 代码那边依赖这个类型所以就调用失败了。

3）其它版本验证

因为反馈是 2.7.7 出错，所以先思考到在之前的版本是否性能失常，于是把服务提供者切换到 dubbo 2.7.3，发现调用依然有谬误，如下：

2020-12-02T21:52:25.945+0800    INFO    getty/listener.go:85    session{session session-closed, Read Bytes: 4586, Write Bytes: 232, Read Pkgs: 0, Write Pkgs: 1} got error{java exception:org.apache.dubbo.rpc.RpcException: Failed to invoke remote proxy method sayHello to registry://127.0.0.1:2181/org.apache.dubbo.registry.RegistryService?application=demoProvider&dubbo=2.0.2&export=dubbo%3A%2F%2F192.168.0.113%3A12345%2Fcom.funnycode.DemoService%3Fanyhost%3Dtrue%26application%3DdemoProvider%26bind.ip%3D192.168.0.113%26bind.port%3D12345%26deprecated%3Dfalse%26dubbo%3D2.0.2%26dynamic%3Dtrue%26generic%3Dfalse%26group%3Dtc%26interface%3Dcom.funnycode.DemoService%26methods%3DsayHello%26pid%3D23889%26register%3Dtrue%26release%3D2.7.3%26revision%3D1.0.0%26side%3Dprovider%26threads%3D200%26timeout%3D60000%26timestamp%3D1606916702204%26version%3D1.0.0&pid=23889&registry=zookeeper&release=2.7.3&timestamp=1606916702193, cause: Not found method "sayHello" in class com.funnycode.DemoServiceImpl.
org.apache.dubbo.rpc.RpcException: Failed to invoke remote proxy method sayHello to registry://127.0.0.1:2181/org.apache.dubbo.registry.RegistryService?application=demoProvider&dubbo=2.0.2&export=dubbo%3A%2F%2F192.168.0.113%3A12345%2Fcom.funnycode.DemoService%3Fanyhost%3Dtrue%26application%3DdemoProvider%26bind.ip%3D192.168.0.113%26bind.port%3D12345%26deprecated%3Dfalse%26dubbo%3D2.0.2%26dynamic%3Dtrue%26generic%3Dfalse%26group%3Dtc%26interface%3Dcom.funnycode.DemoService%26methods%3DsayHello%26pid%3D23889%26register%3Dtrue%26release%3D2.7.3%26revision%3D1.0.0%26side%3Dprovider%26threads%3D200%26timeout%3D60000%26timestamp%3D1606916702204%26version%3D1.0.0&pid=23889&registry=zookeeper&release=2.7.3&timestamp=1606916702193, cause: Not found method "sayHello" in class com.funnycode.DemoServiceImpl.
        at org.apache.dubbo.rpc.proxy.AbstractProxyInvoker.invoke(AbstractProxyInvoker.java:107)
        at org.apache.dubbo.config.invoker.DelegateProviderMetaDataInvoker.invoke(DelegateProviderMetaDataInvoker.java:56)
        at org.apache.dubbo.rpc.protocol.InvokerWrapper.invoke(InvokerWrapper.java:56)
        at org.apache.dubbo.rpc.filter.ExceptionFilter.invoke(ExceptionFilter.java:55)
        at org.apache.dubbo.rpc.protocol.ProtocolFilterWrapper$1.invoke(ProtocolFilterWrapper.java:82)
        at org.apache.dubbo.monitor.support.MonitorFilter.invoke(MonitorFilter.java:92)
        at org.apache.dubbo.rpc.protocol.ProtocolFilterWrapper$1.invoke(ProtocolFilterWrapper.java:82)
        at org.apache.dubbo.rpc.filter.TimeoutFilter.invoke(TimeoutFilter.java:48)
        at org.apache.dubbo.rpc.protocol.ProtocolFilterWrapper$1.invoke(ProtocolFilterWrapper.java:82)
        at org.apache.dubbo.rpc.protocol.dubbo.filter.TraceFilter.invoke(TraceFilter.java:81)
        at org.apache.dubbo.rpc.protocol.ProtocolFilterWrapper$1.invoke(ProtocolFilterWrapper.java:82)
        at org.apache.dubbo.rpc.filter.ContextFilter.invoke(ContextFilter.java:96)
        at org.apache.dubbo.rpc.protocol.ProtocolFilterWrapper$1.invoke(ProtocolFilterWrapper.java:82)
        at org.apache.dubbo.rpc.filter.GenericFilter.invoke(GenericFilter.java:148)
        at org.apache.dubbo.rpc.protocol.ProtocolFilterWrapper$1.invoke(ProtocolFilterWrapper.java:82)
        at org.apache.dubbo.rpc.filter.ClassLoaderFilter.invoke(ClassLoaderFilter.java:38)
        at org.apache.dubbo.rpc.protocol.ProtocolFilterWrapper$1.invoke(ProtocolFilterWrapper.java:82)
        at org.apache.dubbo.rpc.filter.EchoFilter.invoke(EchoFilter.java:41)
        at org.apache.dubbo.rpc.protocol.ProtocolFilterWrapper$1.invoke(ProtocolFilterWrapper.java:82)
        at org.apache.dubbo.rpc.protocol.ProtocolFilterWrapper$CallbackRegistrationInvoker.invoke(ProtocolFilterWrapper.java:157)
        at org.apache.dubbo.rpc.protocol.dubbo.DubboProtocol$1.reply(DubboProtocol.java:152)
        at org.apache.dubbo.remoting.exchange.support.header.HeaderExchangeHandler.handleRequest(HeaderExchangeHandler.java:102)
        at org.apache.dubbo.remoting.exchange.support.header.HeaderExchangeHandler.received(HeaderExchangeHandler.java:193)
        at org.apache.dubbo.remoting.transport.DecodeHandler.received(DecodeHandler.java:51)
        at org.apache.dubbo.remoting.transport.dispatcher.ChannelEventRunnable.run(ChannelEventRunnable.java:57)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
        at java.lang.Thread.run(Thread.java:748)
Caused by: org.apache.dubbo.common.bytecode.NoSuchMethodException: Not found method "sayHello" in class com.funnycode.DemoServiceImpl.
        at org.apache.dubbo.common.bytecode.Wrapper1.invokeMethod(Wrapper1.java)
        at org.apache.dubbo.rpc.proxy.javassist.JavassistProxyFactory$1.doInvoke(JavassistProxyFactory.java:47)
        at org.apache.dubbo.rpc.proxy.AbstractProxyInvoker.invoke(AbstractProxyInvoker.java:84)
        ... 27 more
}, will be closed.

尽管和 2.7.7 的代码是不一样的，然而通过谬误也能看进去是在代理加强类外面办法找不到，大概率是反射找不到办法，所以归根结底也是参数的问题。

4）修复问题

修复绝对简略，就是拿到 struct 定义的 JavaClassName。

case reflect.Struct:
  v, ok := v.(hessian.POJO)
  if ok {return v.JavaClassName()
  }
  return "java.lang.Object"

5）验证后果

再次执行消费者，运行（提供方 2.7.7 和 2.7.3）失常，输入如下：

[2020-12-03/20:04:06 main.main: client.go: 29] response result: Hello tc
...
[2020-12-03/20:04:09 main.main: client.go: 41] response result: Hello tc You are 18
...
[2020-12-03/20:04:09 main.main: client.go: 48] response result: Hello tc You are 18

细节叨叨

1. 如何配置 dubbogo 消费者

仔细的你是否曾经发现，在我 dubbogo 的生产端接口叫 DemoProvider，而后发现提供者叫 DemoService，这个又是如何失常运行的？

实际上和 client.yml 中配置项 references 无关，在配置文件具体阐明了 interface，version，group 等，你还能够通过 methods 配置办法的超时工夫等信息。

references:
  "DemoProvider":
    # 能够指定多个 registry，应用逗号隔开; 不指定默认向所有注册核心注册
    registry: "zk1"
    protocol: "dubbo"
    interface: "com.funnycode.DemoService"
    cluster: "failover"
    version: "1.0.0"
    group: "tc"
    methods:
      - name: "SayHello"
        retries: 3
    ......

2. 全局的 group 和 version 怎么配置

配置文件如下：

# application config
application:
  organization: "dubbogoproxy.com"
  name: "Demo Micro Service"
  module: "dubbogoproxy tc client"
  version: "1.0.0"
  group: "tc"
  owner: "ZX"
  environment: "dev"

references:
  "DemoProvider":
    # 能够指定多个 registry，应用逗号隔开; 不指定默认向所有注册核心注册
    registry: "zk1"
    protocol: "dubbo"
    interface: "com.funnycode.DemoService"
    cluster: "failover"
#    version: "1.0.0"
#    group: "tc"
    methods:
      - name: "SayHello"
        retries: 3

从应用的习惯来讲，必定是 application 示意了全局的配置，然而我发现启动的时候在 application 配置的 version 和 group 并不会赋值给接口，启动会报服务提供方找不到，如下：

2020-12-03T20:15:42.208+0800    DEBUG   zookeeper/registry.go:237       Create a zookeeper node:/dubbo/com.funnycode.DemoService/consumers/consumer%3A%2F%2F30.11.176.107%2FDemoProvider%3Fapp.version%3D1.0.0%26application%3DDemo+Micro+Service%26async%3Dfalse%26bean.name%3DDemoProvider%26cluster%3Dfailover%26environment%3Ddev%26generic%3Dfalse%26group%3D%26interface%3Dcom.funnycode.DemoService%26ip%3D30.11.176.107%26loadbalance%3D%26methods.SayHello.loadbalance%3D%26methods.SayHello.retries%3D3%26methods.SayHello.sticky%3Dfalse%26module%3Ddubbogoproxy+tc+client%26name%3DDemo+Micro+Service%26organization%3Ddubbogoproxy.com%26owner%3DZX%26pid%3D38692%26protocol%3Ddubbo%26provided-by%3D%26reference.filter%3Dcshutdown%26registry.role%3D0%26release%3Ddubbo-golang-1.3.0%26retries%3D%26side%3Dconsumer%26sticky%3Dfalse%26timestamp%3D1606997742%26version%3D

version 和 group 都是空。必须把 DemoProvider 下的 version 和 group 正文关上。

3. 怎么指定调用的办法名

1）go 调用 java

dubbogo 调用 dubbo，因为 go 是大写的办法名，java 外面是小写的办法名，所以会呈现如下谬误：

2020-12-02T17:10:47.739+0800    INFO    getty/listener.go:87    session{session session-closed, Read Bytes: 924, Write Bytes: 199, Read Pkgs: 0, Write Pkgs: 1} got error{java exception:Fail to decode request due to: java.lang.IllegalArgumentException: Service not found:com.funnycode.DemoService, SayHello
java.lang.IllegalArgumentException: Service not found:com.funnycode.DemoService, SayHello
        at org.apache.dubbo.rpc.protocol.dubbo.DecodeableRpcInvocation.decode(DecodeableRpcInvocation.java:134)
        at org.apache.dubbo.rpc.protocol.dubbo.DecodeableRpcInvocation.decode(DecodeableRpcInvocation.java:80)
        at org.apache.dubbo.remoting.transport.DecodeHandler.decode(DecodeHandler.java:57)
        at org.apache.dubbo.remoting.transport.DecodeHandler.received(DecodeHandler.java:44)
        at org.apache.dubbo.remoting.transport.dispatcher.ChannelEventRunnable.run(ChannelEventRunnable.java:57)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
        at java.lang.Thread.run(Thread.java:748)
}, will be closed.

仔细的读者可能曾经留神到了，我在生产端的接口申明是有个 dubbo:"sayHello" 的，示意办法名是 sayHello，这样在服务提供方就能够失去 sayHello 这个办法名。

还有我申明的三个办法都指明它们的办法名叫 dubbo:"sayHello"，这是因为 Java 能够办法名字一样进行重载，而 go 是不能办法名反复的。

2）go 调用 go

间接贴能跑通的代码。

我的提供者接口：

type DemoProvider struct{}

func (p *DemoProvider) SayHello(ctx context.Context, name string) (string, error) {return "Hello" + name, nil}

func (p *DemoProvider) SayHello4(ctx context.Context, user *User) (string, error) {return "Hello" + user.Name + "You are" + strconv.Itoa(user.Age), nil
}

func (p *DemoProvider) SayHello5(ctx context.Context, user *User, name string) (string, error) {return "Hello" + name + "You are" + strconv.Itoa(user.Age), nil
}

func (p *DemoProvider) Reference() string {return "DemoProvider"}

func (p *DemoProvider) MethodMapper() map[string]string {return map[string]string{"SayHello": "sayHello",}
}

我的消费者接口：

type DemoProvider struct {
  // 调用 java 和 go
    SayHello  func(ctx context.Context, name string) (string, error)             `dubbo:"sayHello"`
  // 只调用 java
    SayHello2 func(ctx context.Context, user *User) (string, error)              `dubbo:"sayHello"`
    SayHello3 func(ctx context.Context, user *User, name string) (string, error) `dubbo:"sayHello"`
  // 只调用 go
    SayHello4 func(ctx context.Context, user *User) (string, error)
    SayHello5 func(ctx context.Context, user *User, name string) (string, error)
}

启动服务消费者：

func main() {config.Load()
    gxlog.CInfo("\n\n\nstart to test dubbo")

    res, err := demoProvider.SayHello(context.TODO(), "tc")
    if err != nil {panic(err)
    }

    gxlog.CInfo("response result: %v\n", res)

    user := &User{
        Name: "tc",
        Age:  18,
    }

    res, err = demoProvider.SayHello4(context.TODO(), user)
    if err != nil {panic(err)
    }

    gxlog.CInfo("response result: %v\n", res)

    res, err = demoProvider.SayHello5(context.TODO(), user, "tc")
    if err != nil {panic(err)
    }

    gxlog.CInfo("response result: %v\n", res)

    initSignal()}

这里须要留神 MethodMapper 办法，有时候须要在这个办法中配置办法名的映射关系，否则还是会呈现找不到办法的谬误。

比方因为配置 dubbo:"sayHello"，所以在 go 外面申请 SayHello 变成了 sayHello，那么服务提供方通过 MethodMapper 办法配置后使得提供方也是 sayHello，这样 go 和 java 下裸露的都是小写的 sayHello。

4. 为什么会用 hessian2

老司机都懂，在 dubbo 中 SPI 机制的默认值就是 hessian2

@SPI("hessian2")
public interface Serialization {}

而在 dubbo-go 中：

func NewDubboCodec(reader *bufio.Reader) *ProtocolCodec {s, _ := GetSerializerById(constant.S_Hessian2)
    return &ProtocolCodec{
        reader:     reader,
        pkgType:    0,
        bodyLen:    0,
        headerRead: false,
        serializer: s.(Serializer),
    }
}

5. hessian 序列化源码

能够自行断点查看，两边基本上一样，我也是通过两边比进去的，RpcInvocation.getParameterTypesDesc() 就是办法的参数.

  • go 代码 protocol/dubbo/impl/hessian.go:120#marshalRequest
  • java 代码 org.apache.dubbo.rpc.protocol.dubbo.DubboCodec#encodeRequestData(org.apache.dubbo.remoting.Channel, org.apache.dubbo.common.serialize.ObjectOutput, java.lang.Object, java.lang.String)

6. dubbogo 服务提供者的办法对象须要是指针对象

之前的例子都是 copy 的，这次是纯手打的，才发现了这个问题。
如果你的提供相似：func (p *DemoProvider) SayHello4(ctx context.Context, user User) (string, error)，那么会呈现如下谬误：

2020-12-03T12:42:32.834+0800    ERROR   getty/listener.go:280   OnMessage panic: reflect: Call using *main.User as type main.User
github.com/apache/dubbo-go/remoting/getty.(*RpcServerHandler).OnMessage.func1

参数外面的 User 须要改成 *User。

7. dubbogo 服务消费者的办法对象能够是非指针对象 

SayHello4 func(ctx context.Context, user *User) (string, error)
// or
SayHello4 func(ctx context.Context, user User) (string, error)

因为在参数序列化的时候会对指针做操作：

t := reflect.TypeOf(v)
if reflect.Ptr == t.Kind() {t = reflect.TypeOf(reflect.ValueOf(v).Elem())
}

残缺代码

8. 配置文件阐明

dubbogo 次要有三个配置文件：

  • server.yaml 服务提供方的配置文件
  • client.yaml 服务生产方的配置文件
  • log.yaml 日志文件

如果你什么都不配置，会呈现：

2021/01/11 15:31:41 [InitLog] warn: log configure file name is nil
2021/01/11 15:31:41 [consumerInit] application configure(consumer) file name is nil
2021/01/11 15:31:41 [providerInit] application configure(provider) file name is nil

这样是没法失常应用的。如果你是服务提供方，必须要配置 server.yaml 文件，如果你是服务生产方，必须要配置 client.yaml，理论咱们的利用应该既是消费者又是提供者，所以往往两个文件都是须要配置的。

服务提供方失常启动是会有如下输入的：

2021-01-11T15:36:55.003+0800    INFO    protocol/protocol.go:205        The cached exporter keys is dubbo://:20000/DemoProvider?accesslog=&app.version=1.0.0&application=Demo+Micro+Service&auth=&bean.name=DemoProvider&cluster=failover&environment=dev&execute.limit=&execute.limit.rejected.handler=&group=tc&interface=com.funnycode.DemoService&loadbalance=random&methods.SayHello.loadbalance=random&methods.SayHello.retries=3&methods.SayHello.tps.limit.interval=&methods.SayHello.tps.limit.rate=&methods.SayHello.tps.limit.strategy=&methods.SayHello.weight=0&methods.SayHello4.loadbalance=random&methods.SayHello4.retries=3&methods.SayHello4.tps.limit.interval=&methods.SayHello4.tps.limit.rate=&methods.SayHello4.tps.limit.strategy=&methods.SayHello4.weight=0&methods.SayHello5.loadbalance=random&methods.SayHello5.retries=3&methods.SayHello5.tps.limit.interval=&methods.SayHello5.tps.limit.rate=&methods.SayHello5.tps.limit.strategy=&methods.SayHello5.weight=0&module=dubbogoproxy+tc+client&name=Demo+Micro+Service&organization=dubbogoproxy.com&owner=ZX&param.sign=&registry.role=3&release=dubbo-golang-1.3.0&retries=&serialization=&service.filter=echo%2Ctoken%2Caccesslog%2Ctps%2Cgeneric_service%2Cexecute%2Cpshutdown&side=provider&ssl-enabled=false&timestamp=1610350614&tps.limit.interval=&tps.limit.rate=&tps.limit.rejected.handler=&tps.limit.strategy=&tps.limiter=&version=1.0.0&warmup=100!
2021-01-11T15:36:55.003+0800    INFO    dubbo/dubbo_protocol.go:86      Export service: dubbo://:20000/DemoProvider?accesslog=&app.version=1.0.0&application=Demo+Micro+Service&auth=&bean.name=DemoProvider&cluster=failover&environment=dev&execute.limit=&execute.limit.rejected.handler=&group=tc&interface=com.funnycode.DemoService&loadbalance=random&methods.SayHello.loadbalance=random&methods.SayHello.retries=3&methods.SayHello.tps.limit.interval=&methods.SayHello.tps.limit.rate=&methods.SayHello.tps.limit.strategy=&methods.SayHello.weight=0&methods.SayHello4.loadbalance=random&methods.SayHello4.retries=3&methods.SayHello4.tps.limit.interval=&methods.SayHello4.tps.limit.rate=&methods.SayHello4.tps.limit.strategy=&methods.SayHello4.weight=0&methods.SayHello5.loadbalance=random&methods.SayHello5.retries=3&methods.SayHello5.tps.limit.interval=&methods.SayHello5.tps.limit.rate=&methods.SayHello5.tps.limit.strategy=&methods.SayHello5.weight=0&module=dubbogoproxy+tc+client&name=Demo+Micro+Service&organization=dubbogoproxy.com&owner=ZX&param.sign=&registry.role=3&release=dubbo-golang-1.3.0&retries=&serialization=&service.filter=echo%2Ctoken%2Caccesslog%2Ctps%2Cgeneric_service%2Cexecute%2Cpshutdown&side=provider&ssl-enabled=false&timestamp=1610350614&tps.limit.interval=&tps.limit.rate=&tps.limit.rejected.handler=&tps.limit.strategy=&tps.limiter=&version=1.0.0&warmup=100

9. 复现代码

  • https://github.com/cityiron/java_study/tree/master/dubbo2.7.7/dg-issue900
  • https://github.com/cityiron/golang_study/tree/master/dubbogo/1.5.4/arg-bug

参考

  • https://dubbo.apache.org/zh/docs/v2.7/user/configuration/api/
  • https://github.com/apache/dubbo-go/issues/257

篇幅无限，就介绍到这里。欢送有趣味的同学参加 dubbogo3.0 的建设，感激浏览。如果你有任何疑难，欢送钉钉搜寻群号：31363295，退出交换群。

作者简介

铁城 (GithubID cityiron)，dubbo-go 社区 committer，次要参加 dubbo-go 1.5 版本迭代、dubbo-go 3.0 服务路由和云原生方面工作、以及 dubbo-go-proxy 我的项目负责人。善于应用 Java/Go 语言，专一于云原生和微服务等技术方向。

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