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

原创
02/09 19:05
阅读数 714

作者 | 铁城   dubbo-go 社区 committer

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


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"}

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); } ...... }}

  • 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。

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);}


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 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 configapplication: 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 versiongroup 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

versiongroup 都是空。必须把 DemoProvider 下的 versiongroup 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, SayHellojava.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.

  • g o 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.Usergithub.com/apache/dubbo-go/remoting/getty.(*RpcServerHandler).OnMessage.func1

参数里面 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)// orSayHello4 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 nil2021/01/11 15:31:41 [consumerInit] application configure(consumer) file name is nil2021/01/11 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


  • 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


篇幅有限,就介绍到这里。欢迎有兴趣的同学点击【阅读原文】参与 dubbogo3.0 的建设,感谢阅读。 如果你有任何疑问,欢迎钉钉扫码加入交流群【或搜索钉钉群号 31363295】:

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。
戳原文,立即参与 dubbogo3.0 的建设!
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