RPC 之 windows上使用thrift

摘要:apache thrift作为著名的跨语言,跨平台的RPC框架已经得到了大量应用,比如Hadoop, Cassandra等。与早期的CORBA, DCOM, 以致传统的WebService如基于XML-RPC的 SOAP协议和基于http的restfull ws相比较,其强大的功能和性能以及开发效率都让人侧目。本文目的在于在windows上使用thrift编译一个RPC的java客户端和服务器来体验其使用。

关键字
: RPC , thrift

1.下载和安装thrift
到 http://apache.fayea.com/thrift/0.9.2/thrift-0.9.2.exe 下载,可直接将下载目录加到Windows环境变量,以便可以随时敲thrift-0.9.2命令。

2.编译tutorial.thrift文件为java 代码:
 到 https://git1-us-west.apache.org/repos/asf?p=thrift.git;a=tree;f=tutorial;hb=HEAD 下载tutorial.thrift和shared.thrift 2个文件 ,  先执行   thrift-0.9.2 -gen java  tutorial\shared.thrift  然后执行  thrift-0.9.2 -gen java  tutorial\tutorial.thrift , 可以发现生成了gen-java目录,
 将生成的java 类 进行编译会报错,放于eclipse工程中会发现很多包缺失,比如org.apache.thrift.* ;
 org.apache.thrift报缺失是因为thrift的java类库需要构建出来。如果我们只下载了thrift-0.9.2.exe 那么是不带thrift-0.9.2.jar这个类库的。
 可以下载thrift的源码 (http://mirrors.hust.edu.cn/apache/thrift/0.9.2/thrift-0.9.2.tar.gz)将其解压,到目录lib\java下执行ant (需要之前安装java和ant,并将ant folder\bin加到环境变量).会生成lib\java\build,其下有thrift-0.9.2.jar

3. 写自己的客户端和服务器程序:
添加CalculatorHandler.java :

import java.util.HashMap;
import tutorial.Calculator;
import tutorial.InvalidOperation;
import tutorial.SharedStruct;
import tutorial.Work;

public class CalculatorHandler implements Calculator.Iface {

    private HashMap<Integer, SharedStruct> log;

    public CalculatorHandler() {
        log = new HashMap<Integer, SharedStruct>();
    }

    public void ping() {
        System.out.println("ping()");
    }

    public int add(int n1, int n2) {
        System.out.println("add(" + n1 + "," + n2 + ")");
        return n1 + n2;
    }

    public int calculate(int logid, Work work) throws InvalidOperation {
        System.out.println("calculate(" + logid + ", {" + work.op + ","
                + work.num1 + "," + work.num2 + "})");
        int val = 0;
        switch (work.op) {
        case ADD:
            val = work.num1 + work.num2;
            break;
        case SUBTRACT:
            val = work.num1 - work.num2;
            break;
        case MULTIPLY:
            val = work.num1 * work.num2;
            break;
        case DIVIDE:
            if (work.num2 == 0) {
                InvalidOperation io = new InvalidOperation();
                io.what = work.op.getValue();
                io.why = "Cannot divide by 0";
                throw io;
            }
            val = work.num1 / work.num2;
            break;
        default:
            InvalidOperation io = new InvalidOperation();
            io.what = work.op.getValue();
            io.why = "Unknown operation";
            throw io;
        }

        SharedStruct entry = new SharedStruct();
        entry.key = logid;
        entry.value = Integer.toString(val);
        log.put(logid, entry);

        return val;
    }

    public SharedStruct getStruct(int key) {
        System.out.println("getStruct(" + key + ")");
        return log.get(key);
    }

    public void zip() {
        System.out.println("zip()");
    }

}
<strong>
</strong>
添加client.java :
import org.apache.thrift.TException;
import org.apache.thrift.protocol.TBinaryProtocol;
import org.apache.thrift.protocol.TProtocol;
import org.apache.thrift.transport.TSocket;
import org.apache.thrift.transport.TTransport;

import tutorial.Calculator;
import tutorial.InvalidOperation;
import tutorial.Operation;
import tutorial.SharedStruct;
import tutorial.Work;

public class Client {
    
    
    static void simple() throws Exception {
        TTransport transport =  new TSocket("localhost", 9090);
        transport.open();

        TProtocol protocol = new  TBinaryProtocol(transport);
        Calculator.Client client = new Calculator.Client(protocol);

        perform(client);

        transport.close();

        
    }
    
    private static void perform(Calculator.Client client) throws TException
      {
        client.ping();
        System.out.println("ping()");

        int sum = client.add(1,1);
        System.out.println("1+1=" + sum);

        Work work = new Work();

        work.op = Operation.DIVIDE;
        work.num1 = 1;
        work.num2 = 0;
        try {
          int quotient = client.calculate(1, work);
          System.out.println("Whoa we can divide by 0");
        } catch (InvalidOperation io) {
          System.out.println("Invalid operation: " + io.why);
        }

        work.op = Operation.SUBTRACT;
        work.num1 = 15;
        work.num2 = 10;
        try {
          int diff = client.calculate(1, work);
          System.out.println("15-10=" + diff);
        } catch (InvalidOperation io) {
          System.out.println("Invalid operation: " + io.why);
        }

        SharedStruct log = client.getStruct(1);
        System.out.println("Check log: " + log.value);
      }


    /**
     * @param args
     * @throws Exception
     */
    public static void main(String[] args) throws Exception {
        simple();

    }

}
添加server.java :

import org.apache.thrift.server.TServer;
import org.apache.thrift.server.TServer.Args;
import org.apache.thrift.transport.TServerSocket;
import org.apache.thrift.transport.TServerTransport;
import org.apache.thrift.server.TSimpleServer;

import tutorial.Calculator;

public class Server {

    static final int port_Simple = 9090;

    public static void simple(Calculator.Processor processor) {
        try {
            // Args arg = null;
            TServerTransport serverTransport = new TServerSocket(port_Simple);
            TServer server = new TSimpleServer(    new Args(serverTransport).processor(processor));

            // Use this for a multithreaded server
            // TServer server = new TThreadPoolServer(new TThreadPoolServer.Args(serverTransport).processor(processor));

            System.out.println("Starting the simple server...");
            server.serve();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    /**
     * @param args
     */
    public static void main(String[] args) {
        CalculatorHandler handler = new CalculatorHandler();
        Calculator.Processor processor = new Calculator.Processor(handler);

        simple(processor);

    }

}

---引用jar: libthrift-0.9.2.jar, slf4j-*.jar

4.启动 server,再运行client可以看到客户端输出:

ping()
1+1=2
Invalid operation: Cannot divide by 0
15-10=5
Check log: 5


总结:
1. thrift缺点:

  1)文档少,初学者要花较长时间来琢磨如何写出第一个基于thrift RPC的C/S程序.
  2)文档bug多,文档描述与实际运行的行为不符。比如根据文档的tutorial/tutorial.thrift来生成Java代码时 并没有生成shared.SharedService类。
  3)windows上的thrift编译器(比如thrift-0.9.2.exe)有bug,对于thrift文件中的include指示符支持不好。

2. thrift优点:

  1)跨平台,跨/多语言的支持非常好。比如一个运行在Windows上的c#客户端完全可以访问一个运行在Linux机器上的用Java实现的服务器端。
    thrift编译器可以根据thrift文件编译出针对当下几乎所有流行语言的代码()。
  2)性能好。 如果服务端代码用c/c++则性能更是杠杠的。
  3)开发效率高,手工代码量小。  thrift编译器所生成的代码基本上拿来即可使用,(需要增加服务端代码来实现自己的业务逻辑,但是协议实现,数据类型实现都已经自动生成)。
  4)兼容性好。如果thrift文件更改,那么之前基于老thrift文件的程序仍能良好运行。
 
参考资料:

1. Apache thrift网站:http://thrift.apache.org/
2. RPC性能比较: http://www.useopen.net/blog/2015/rpc-performance.html
3. 董西城的博客: http://dongxicheng.org/search-engine/thrift-rpc/


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