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Posted to commits@dubbo.apache.org by il...@apache.org on 2021/02/20 03:10:38 UTC
[dubbo-website] branch master updated: add new blog
'dubbogo-from-scratch'
This is an automated email from the ASF dual-hosted git repository.
iluo pushed a commit to branch master
in repository https://gitbox.apache.org/repos/asf/dubbo-website.git
The following commit(s) were added to refs/heads/master by this push:
new 8b53d41 add new blog 'dubbogo-from-scratch'
8b53d41 is described below
commit 8b53d41c8f9791e3d9f5ed7d13d120497d317abf
Author: Ian Luo <ia...@gmail.com>
AuthorDate: Sat Feb 20 11:08:20 2021 +0800
add new blog 'dubbogo-from-scratch'
---
content/zh/blog/news/dubbogo-from-scratch.md | 847 ++++++++++++++++++++++
static/imgs/blog/dubbo-go/from-scratch/dfsa01.jpg | Bin 0 -> 212105 bytes
static/imgs/blog/dubbo-go/from-scratch/dfsa02.png | Bin 0 -> 1159711 bytes
3 files changed, 847 insertions(+)
diff --git a/content/zh/blog/news/dubbogo-from-scratch.md b/content/zh/blog/news/dubbogo-from-scratch.md
new file mode 100644
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@@ -0,0 +1,847 @@
+---
+title: "dubbo-go 白话文"
+linkTitle: "dubbo-go 白话文"
+date: 2021-02-20
+description: >
+ 本文手把手教你使用 dubbogo 调用 dubbogo 或 dubbo 提供的服务提供方
+---
+
+
+
+## 一、前言
+
+
+> 本文基于 dubbogo [1.5.4](https://github.com/apache/dubbo-go/releases/tag/v1.5.4) 版本
+
+
+
+最近开始参与 dubbogo 的一些开发测试，之前都是直接拿 [samples](https://github.com/apache/dubbo-go-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
+
+
+
+## 二、解决问题
+
+
+### 2.1 准备 dubbo 服务提供者
+
+
+#### 2.1.1 基本定义
+
+
+定义 `DemoService` 接口：
+
+
+```java
+public interface DemoService {
+
+ String sayHello(String name);
+
+ String sayHello(User user);
+
+ String sayHello(User user, String name);
+
+}
+```
+
+
+定义 `User` 对象：
+
+
+```java
+public class User implements Serializable {
+
+ private String name;
+
+ private int age;
+
+ ......
+}
+```
+
+
+#### 2.1.2 启动 dubbo 服务提供者
+
+
+用的 [dubbo 官方示例代码](http://dubbo.apache.org/zh/docs/v2.7/user/configuration/api/):
+
+
+```java
+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：
+
+
+```bash
+$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。
+
+
+### 2.2 准备 dubbogo 服务消费者
+
+
+#### 2.2.1 基本定义
+
+
+定义 `User` 对象：
+
+
+```go
+type User struct {
+ Name string
+ Age int
+}
+
+func (User) JavaClassName() string {
+ return "com.funnycode.User"
+}
+```
+
+
+定义 `DemoProvider` 接口：
+
+
+```go
+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"
+}
+```
+
+
+#### 2.2.2 启动 dubbogo 消费者
+
+
+```go
+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()
+}
+```
+
+
+### 2.3 请求结果分析
+
+
+#### 2.3.1 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：
+
+
+```bash
+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](https://github.com/apache/dubbo-go/issues/900) 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`。
+
+
+#### 2.3.2 断点查看
+
+
+代码如下：
+
+
+```java
+// 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：
+
+
+```java
+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。
+
+
+
+
+
+### 2.4 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。
+
+
+
+#### 2.4.1 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。
+
+
+```java
+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);
+}
+```
+
+
+
+
+
+desc 肉眼可见的是 `Lcom/funnycode/User`，这个就是正确的对象了。
+
+
+#### 2.4.2 查找 dubbogo 为什么不对
+
+
+代码位置：
+
+
+`protocol/dubbo/impl/hessian.go:120#marshalRequest`
+
+
+代码实现：
+
+
+```go
+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`
+
+
+
+```go
+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。
+
+
+#### 2.4.3 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：
+
+
+```bash
+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% [...]
+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%3Dsay [...]
+ 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。
+
+
+#### 2.4.4 修复问题
+
+
+修复相对简单，就是拿到 `struct` 定义的 `JavaClassName`。
+
+
+```go
+case reflect.Struct:
+ v, ok := v.(hessian.POJO)
+ if ok {
+ return v.JavaClassName()
+ }
+ return "java.lang.Object"
+```
+
+
+#### 2.4.3 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：
+
+
+```bash
+[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
+```
+
+
+## 三、细节叨叨
+
+
+### 3.1 如何配置 dubbgo 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 `interface`，`version`，`group` 等，你还可以通过 methods 配置方法的超时时间等信息。
+
+
+```yaml
+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
+ ......
+```
+
+
+### 3.2 全局的 group 和 version 怎么配置
+
+
+配置文件如下：
+
+
+```yaml
+# 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：
+
+
+```bash
+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.retrie [...]
+```
+
+
+`version` 和 `group` 都是空。必须把 `DemoProvider` 下的 `version` 和 `group` 注释打开。
+
+
+### 3.3 怎么指定调用的方法名
+
+
+#### 3.3.1 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：
+
+
+```bash
+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。
+
+
+#### 3.3.2 go 调用 go
+
+
+> 直接贴能跑通的代码
+
+
+
+我的提供者接口：
+
+
+```go
+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：
+
+
+```go
+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：
+
+
+```go
+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`。
+
+
+### 3.4 为什么会用 hessian2
+
+
+老司机都懂，在 dubbo 中 SPI 机制的默认值就是 hessian2
+
+
+```java
+@SPI("hessian2")
+public interface Serialization {
+}
+```
+
+
+而在 dubbo-go 中：
+
+
+```go
+func NewDubboCodec(reader *bufio.Reader) *ProtocolCodec {
+ s, _ := GetSerializerById(constant.S_Hessian2)
+ return &ProtocolCodec{
+ reader: reader,
+ pkgType: 0,
+ bodyLen: 0,
+ headerRead: false,
+ serializer: s.(Serializer),
+ }
+}
+```
+
+
+### 3.5 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)`
+
+
+
+### 3.6 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：
+
+
+```bash
+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`。
+
+
+### 3.7 dubbogo 服务消费者的方法对象可以是非指针对象
+
+
+```go
+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：
+
+
+```go
+t := reflect.TypeOf(v)
+if reflect.Ptr == t.Kind() {
+ t = reflect.TypeOf(reflect.ValueOf(v).Elem())
+}
+```
+
+
+[完整代码](https://github.com/apache/dubbo-go/blob/v1.5.4/protocol/dubbo/impl/hessian.go#L486)
+
+
+### 3.8 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：
+
+
+```bash
+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：
+
+
+```bash
+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 [...]
+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.Sa [...]
+```
+
+
+### 3.9 复现代码
+
+
+- [https://github.com/cityiron/java_study/tree/master/dubbo2.7.7/dg-issue900](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](https://github.com/cityiron/golang_study/tree/master/dubbogo/1.5.4/arg-bug)
+
+
+
+## 四、参考
+
+- [https://dubbo.apache.org/zh/docs/v2.7/user/configuration/api/](https://dubbo.apache.org/zh/docs/v2.7/user/configuration/api/)
+- [https://github.com/apache/dubbo-go/issues/257](https://github.com/apache/dubbo-go/issues/257)
+
+---
+
+
+
+篇幅有限，就介绍到这里。欢迎有兴趣的同学来参与 [dubbogo3.0](https://github.com/apache/dubbo-go/tree/3.0) 的建设，感谢阅读。
+
+
+
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