dubbo-go 白话文 | 从零搭建 dubbogo 和 dubbo 的简单用例

头图.png

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

本文将手把手教你使用 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

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

通过本文你可以了解到:

  • 如何常规配置 dubbogo 消费方去调用 dubbo 和 dubbogo 服务提供方。
  • 通过一个实际的 BUG 介绍解决问题的思路。

解决问题

1. 准备 dubbo 服务提供者

1)基本定义

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 官方示例代码

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

    // 当前应用配置
    ApplicationConfig application = new ApplicationConfig();
    application.setName("demoProvider");

    // 连接注册中心配置
    RegistryConfig registry = new RegistryConfig();
    registry.setAddress("127.0.0.1:2181");
    registry.setProtocol("zookeeper");
    registry.setUsername("");
    registry.setPassword("");

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

    // 注意:ServiceConfig为重对象,内部封装了与注册中心的连接,以及开启服务端口

    // 服务提供者暴露服务配置
    ServiceConfig<DemoService> service = new ServiceConfig<>(); // 此实例很重,封装了与注册中心的连接,请自行缓存,否则可能造成内存和连接泄漏
    service.setApplication(application);
    service.setRegistry(registry); // 多个注册中心可以用setRegistries()
    service.setProtocol(protocol); // 多个协议可以用setProtocols()
    service.setInterface(DemoService.class);
    service.setRef(demoService);
    service.setVersion("1.0.0");
    service.setGroup("tc");
    service.setTimeout(60 * 1000);

    // 暴露及注册服务
    service.export();

    System.in.read();
}

查看 zookeeper 看是否注册成功:

$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]
```

如上的输出表示服务提供方已经启动。

## 2. 准备 dubbogo 服务消费者

### 1)基本定义

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. 请求结果分析

### 1)直接调用

> 确认问题的存在。

第一个接口的参数是字符串,可以正常返回 `[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,无法调用成功。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.

错误正如 issue 中描述的一模一样,因为错误信息返回到了消费端,可以看到 Java 那边的错误堆栈信息,所以直接去看 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) {
          // 方法描述里面根据方法名查找
          MethodDescriptor methodDescriptor = serviceDescriptor.getMethod(getMethodName(), desc);
          if (methodDescriptor != null) {
              pts = methodDescriptor.getParameterClasses();
              this.setReturnTypes(methodDescriptor.getReturnTypes());
          }
      }
      // 表示没有找到方法        
      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,即找方法是否存在,存在的话就会设置好 ParameterClasses
  • 如果上面没找到,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方法错误。
  • desc 是 Ljava/lang/Object ,很明显并没有参数是 Object 的方法,所以必然是会报错的。

补充说明:方法查询。
**
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;
}

优点:比之前的版本加了方法的元信息缓存起来,不使用反射可以提高效率,可以理解用空间换时间。

1.jpg

4. 解决问题

因为直接撸代码并 hold 不住,所以通过比较来查看问题所在。

1)启动 dubbo 服务消费者

通过 api 模式启动,参考官方例子。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 {
    // 当前应用配置
    ApplicationConfig application = new ApplicationConfig();
    application.setName("demoProvider2");

    // 连接注册中心配置
    RegistryConfig registry = new RegistryConfig();
    registry.setAddress("127.0.0.1:2181");
    registry.setProtocol("zookeeper");
    registry.setUsername("");
    registry.setPassword("");
    // 注意:ReferenceConfig为重对象,内部封装了与注册中心的连接,以及与服务提供方的连接

    // 引用远程服务
    ReferenceConfig<DemoService> reference
        = new ReferenceConfig<>(); // 此实例很重,封装了与注册中心的连接以及与提供者的连接,请自行缓存,否则可能造成内存和连接泄漏
    reference.setApplication(application);
    reference.setRegistry(registry); // 多个注册中心可以用setRegistries()
    reference.setInterface(DemoService.class);
    reference.setVersion("1.0.0");
    reference.setGroup("tc");
    reference.setCheck(true);
    reference.setTimeout(1000 * 60);

    // 和本地bean一样使用xxxService
    DemoService demoService = reference.get(); // 注意:此代理对象内部封装了所有通讯细节,对象较重,请缓存复用
    System.out.println(demoService.sayHello(new User("tc", 18)));

    TimeUnit.MINUTES.sleep(10);
}

2.png

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

代码位置:
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)
    }

    ......
}

断点可以发现,types 返回的时候就已经是 Object 了,没有返回 User,那么继续跟进去查看代码。

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

  ......

  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"
    }
    ......
}

很明显当发现是 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,所以先考虑到在之前的版本是否功能正常,于是把服务提供者切换到 dubbo 2.7.3,发现调用仍然有错误,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.

虽然和 2.7.7 的代码是不一样的,但是通过错误也能看出来是在代理增强类里面方法找不到,大概率是反射找不到方法,所以归根结底也是参数的问题。

4)修复问题

修复相对简单,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)验证结果

再次执行消费者,运行(提供方 2.7.7 和 2.7.3)正常,输出如下:

[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

细心的你是否已经发现,在我 dubbogo 的消费端接口叫 DemoProvider,然后发现提供者叫 DemoService,这个又是如何正常运行的?

实际上和 client.yml 中配置项 references 有关,在配置文件详细说明了 interfaceversiongroup 等,你还可以通过 methods 配置方法的超时时间等信息。

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

从使用的习惯来讲,肯定是 application 表示了全局的配置,但是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 注释打开。

3. 怎么指定调用的方法名

1)go 调用 java

dubbogo 调用 dubbo,因为 go 是大写的方法名,java 里面是小写的方法名,所以会出现如下错误:

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.

细心的读者可能已经注意到了,我在消费端的接口声明是有个 dubbo:"sayHello" 的,表示方法名是 sayHello,这样在服务提供方就可以得到 sayHello 这个方法名。

还有我声明的三个方法都指明它们的方法名叫 dubbo:"sayHello",这是因为 Java 可以方法名字一样进行重载,而 go 是不能方法名重复的。

2)go 调用 go

直接贴能跑通的代码。

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()
}

这里需要注意 MethodMapper 方法,有时候需要在这个方法中配置方法名的映射关系,否则还是会出现找不到方法的错误。

比如因为配置 dubbo:"sayHello",所以在 go 里面请求 SayHello 变成了 sayHello,那么服务提供方通过 MethodMapper 方法配置后使得提供方也是 sayHello,这样 go 和 java 下暴露的都是小写的 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

可以自行断点查看,两边基本上一样,我也是通过两边比出来的,RpcInvocation.getParameterTypesDesc() 就是方法的参数.

  • 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 服务提供者的方法对象需要是指针对象

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

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

参数里面的 User 需要改成 *User

7. dubbogo 服务消费者的方法对象可以是非指针对象

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())
}

完整代码

8. 配置文件说明

dubbogo 主要有三个配置文件:

  • server.yaml 服务提供方的配置文件
  • client.yaml 服务消费方的配置文件
  • log.yaml 日志文件

如果你什么都不配置,会出现:

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

这样是没法正常使用的。如果你是服务提供方,必须要配置 server.yaml 文件,如果你是服务消费方,必须要配置 client.yaml,实际我们的应用应该既是消费者又是提供者,所以往往两个文件都是需要配置的。

服务提供方正常启动是会有如下输出的:

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

参考

篇幅有限,就介绍到这里。欢迎有兴趣的同学参与 dubbogo3.0 的建设,感谢阅读。

作者简介

铁城(GithubID cityiron),dubbo-go 社区 committer,主要参与 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 项目负责人。擅长使用 Java/Go 语言,专注于云原生和微服务等技术方向。

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