Apache Thrift RPC在分布式环境中的Java方法实现

Question

我的项目简要描述： 我正在写一个名为“GreetingsNode”的java类，它在分布式环境中工作，其中有一个“managementNode”作为服务存储库并接收和存储其他节点的信息（主机端口号和所提供的服务），并分发由注册服务提供的方法的RPC。如果一个节点可以回答RPC，则打开一个节点套接字并在主叫节点和应答节点之间建立连接，并且应答节点返回结果。

我使用Apache thrift作为IDL和RPC的框架。

现在的问题。 My GreetingsNodeHandler类实现了一个包含单个方法“getHello（user）”（用户是包含节点名称的结构，它是GreetingsNode类的构造函数的参数）的简单节点接口。 当连接到管理节点的GreetingsNode X创建该方法的RPC时，另一个注册的GreetingsNode必须回答消息“hello X”。

我不明白如何实现返回结果的处理程序部分，因此我无法理解应该如何编写junit测试来检查方法实现是否正常工作。

断言像 的assertEquals（client.getHello（用户）.getMessage（）， “John Doe：您好”）

会的工作，但我不明白怎么回事，在我的情况，我应该把客户端部分...

为GreetingService的节俭服务代码：

struct Message { 
    1: string message 
} 

struct User { 
    1: string name 
} 

service GreetingsService { 
    Message getHello(1: User user) 
} 

代码GreetingsServiceHandler必须实现GreetingsService方法getHello（）

public class GreetingsServiceHandler implements GreetingsService.Iface { 

private static Random random = new Random(10); 
private ManagementService.Client managementClient; 
private GreetingsService.Client helloClient; 

@Override 
public Message getHello(User user) throws TException { 
    Message answer = null; 
    // class ServiceProvider is generated by thrift, part of ManagementService thrift service 
    ServiceProvider provider = null; 
    List<ServiceProvider>providers = managementClient.getProvidersForService(user.name); 

    if (providers.isEmpty()) 
     throw new NoProviderAvailableException(); //separate file contains Exception 
    else { 
     provider = providers.get(random.nextInt(providers.size())); 
     //connection between nodes is established here 
     TTransport helloTransport = new TSocket(provider.getHostName(), provider.getPort()); 
     TProtocol helloProtocol = new TBinaryProtocol(helloTransport); 
     helloClient = new GreetingsService.Client(helloProtocol); 
     helloTransport.open(); 

     // here lies my problem 
     answer = helloClient.getHello(user); 
     //if I use this instead, then helloClient variable is clearly not used, but of course I need it to answer the method call 
     answer = answer.setMessage("Ciao " + user.getName() + ", welcome among us!"); 

    } 
    return answer; 

} 

和GreetingsNode代码如下：

public class GreetingsNode implements NodeIface { 

private ThriftServer helloServer; 
private ManagementService.Client managementClient; 
private NodeManifest nodeManifest; 
private User user; 
private String name; 

public GreetingsNode(NodeManifest nodeManifest, String name) { 
    this.nodeManifest = nodeManifest; 
    this.helloServer = new ThriftServer(GreetingsServiceHandler.class); 
    this.name = name; 
} 

@Override 
public void turnOn() throws TException { 

    helloServer.start(); 

    TSocket helloServerTransport = new TSocket("localhost", Constants.SERVER_PORT); 
    TBinaryProtocol helloServerProtocol = new TBinaryProtocol(helloServerTransport); 
    managementClient = new ManagementService.Client(helloServerProtocol); 
    this.setUser(new User(name)); 
    helloServerTransport.open(); 

    helloServer = new ThriftServer(GreetingsServiceHandler.class); 
    //portNegotiator is a class described in a separate file, that handles the registration of other nodes to the managementNode. NodeManifest is a file generated by thrift, part of managementService thrift file, describing a struct that contains hostname and port number of nodes. 
    PortNegotiator negotiator = new PortNegotiator(managementClient); 
    negotiator.negotiate(nodeManifest, helloServer); 

} 

@Override 
public void turnOff() { 
    helloServer.stop(); 
} 

public User getUser() { 
    return user; 
} 

public void setUser(User user) { 
    this.user = user; 
} 

Answer 1

的基本方法在处理IMPL是非常简单的，类似下面应该做的（免责声明：未测试）：

@Override 
public Message getHello(User user) throws TException { 
    Message answer = new Message(); 
    answer = answer.setMessage("Ciao " + user.getName() + ", welcome among us!"); 
    return answer; 
} 

如果我用这个代替，那么helloClient变量显然没有用，但我当然需要它来回答方法调用

当连接到管理节点的GreetingsNode X创建该方法的RPC时，另一个注册的GreetingsNode必须回答消息“hello X”。

如果这意味着我们要像客户端=>服务器A =>服务器B调用序列则这也是可能的，只需要稍作修改。从我们的基本出发例如上面，我们相应提高了代码：

private Message callTheOtherNode(User user) { 
    // class ServiceProvider is generated by Thrift, 
    // part of ManagementService Thrift service 
    ServiceProvider provider = null; 
    List<ServiceProvider>providers = managementClient.getProvidersForService(user.name); 

    if (providers.isEmpty()) 
     throw new NoProviderAvailableException(); //separate file contains Exception 

    provider = providers.get(random.nextInt(providers.size())); 
    //connection between nodes is established here 
    TTransport helloTransport = new TSocket(provider.getHostName(), provider.getPort()); 
    TProtocol helloProtocol = new TBinaryProtocol(helloTransport); 
    helloClient = new GreetingsService.Client(helloProtocol); 
    helloTransport.open(); 
    return helloClient.getHello(user); 
} 

@Override 
public Message getHello(User user) throws TException { 
    Message answer = callTheOtherNode(user); 
    return answer; 
} 

当然，“其他节点”被称为需求真正做到与请求的东西，而不是简单地转发一遍又一节点。