Thrift 的Go與C語言實現

Thrift 是Facebook為了解決各系統間大資料量的傳輸通訊以及系統之間語言環境不同而設計的一種傳輸框架。目前來看常用的主流語言Thrift都已經很好地支援，並且github上已經有很多實現，除了C語言之外。Thrift傳輸的程式的靜態資料，即資料的資料結構必須事前固定。
Thrift原理就不介紹了，理論性東西網上很多，並且都是雷同的。下面通過例項介紹Thrift 介面在Go與C語言下的實現，以及如何在C語言中呼叫Go所編寫的Thrift客戶端。

1. thrift 檔案編寫

#example.thrift

    namespace go
 
 thrift.rpc
    struct Response {
    1: required string data;
    }
service RpcService {
    Response Test(1:string input)
}

2. Go與C的thrift程式碼

thrift -r --gen go example.thrift
thrift -r --gen c_glib example.thrift

此時在目錄下會出現gen-go與gen-c_gib兩個資料夾，裡邊存放著Thrift自動生成的資料結構體以及函式的宣告。

3. Go的server端實現

/* server.go */

package main
import (
    "./gen-go/thrift/rpc"
    "git.apache.org/thrift.git/lib/go/thrift"
    "log"
    "os"
)

const (
    NetworkAddr = "localhost:9090"
)

type RpcServiceImpl struct {
}
func (this *RpcServiceImpl) Test(input string) (r *rpc.Response, err error) {
    //函式具體實現
    return
 

}

func main() {
    transportFactory := thrift.NewTFramedTransportFactory(thrift.NewTTransportFactory())

    protocolFactory := thrift.NewTBinaryProtocolFactoryDefault()

    serverTransport, err := thrift.NewTServerSocket(NetworkAddr)
    if err != nil {
        log.Println("Error!", err)
        os.Exit(1)
    }

    handler := &RpcServiceImpl{}
    processor := rpc.NewRpcServiceProcessor(handler)


    log.Println("thrift server in", NetworkAddr)
    server.Serve()
}

4. Go的客戶端實現

/* client.go */

import (
    "./gen-go/thrift/rpc"
    "fmt"
    "git.apache.org/thrift.git/lib/go/thrift"
    "net"
    "os"
)

func main(){

ip := "127.0.0.1"
port := "9090"
input :=""  

transportFactory := thrift.NewTFramedTransportFactory(thrift.NewTTransportFactory())
    protocolFactory := thrift.NewTBinaryProtocolFactoryDefault()

    tSocket, err := thrift.NewTSocket(net.JoinHostPort(ip, port))
    if err != nil {
        fmt.Fprintln(os.Stderr, "Error resolving address, ", err)
        os.Exit(1)
    }

    tTransport, _ := transportFactory.GetTransport(tSocket)

    client := rpc.NewRpcServiceClientFactory(tTransport, protocolFactory)
    if err := tTransport.Open(); err != nil {
        fmt.Fprintln(os.Stderr, (fmt.Errorf("Error opening socket to %s:%s : %v", ip, port, err)))
        os.Exit(1)
    }
    defer tTransport.Close()

    resp, _ := client.Test(input)
}

C的客戶端實現

C 的客戶端實現目前在github一個都沒有，Thrift好像也是最近才支援的。thrift是一種面向物件的框架，C語言面向物件的實現必須依賴於gobject庫，所以這裡邊在實現的過程中需要注意一點，對thrift檔案中定義的struct，其他可以直接例項化為物件，在C中必須使用g_object_new函式進行初始化，要不然改strcut 將無法實現。在會一直出現無法找到對應結構接收server端傳來的引數。

/* client.c */

#include <stdio.h>
#include <glib-object.h>
#include <string.h>

#include <thrift/c_glib/protocol/thrift_binary_protocol.h>
#include <thrift/c_glib/transport/thrift_framed_transport.h>
#include <thrift/c_glib/transport/thrift_socket.h>
#include "gen-c_glib/rpc_service.h"


struct thrift_if{  

   ThriftSocket *socket;
   ThriftTransport *transport;
   ThriftProtocol *protocol;
   RpcServiceIf *client;

};

void if_open (struct thrift_if* if_instance, gchar *hostname, gint32 port, GError **error){

#if (!GLIB_CHECK_VERSION (2, 36, 0))
    g_type_init ();
#endif

   if_instance->socket = g_object_new (THRIFT_TYPE_SOCKET,
                            "hostname",  hostname,
                            "port",      port,
                            NULL);

   if_instance->transport = g_object_new (THRIFT_TYPE_FRAMED_TRANSPORT,
                            "transport", if_instance->socket,
                            NULL);
    if_instance->protocol  = g_object_new (THRIFT_TYPE_BINARY_PROTOCOL,
                            "transport", if_instance->transport,
                            NULL);

    thrift_transport_open (if_instance->transport, error);

    if(!error){
        return;
    }

    if_instance->client = g_object_new (TYPE_RPC_SERVICE_CLIENT,
                         "input_protocol",  if_instance->protocol,
                         "output_protocol", if_instance->protocol,
                         NULL);

}

void if_close (struct thrift_if *if_instance, GError **error){

    g_clear_error (error); 
    thrift_transport_close (if_instance->transport, NULL);
    g_object_unref (if_instance->client);
    g_object_unref (if_instance->protocol);
    g_object_unref (if_instance->transport);
    g_object_unref (if_instance->socket);
}

int main(){

    gchar *hostname = "127.0.0.1";
    gint32 port = 9090;
    gchar *input = ""

    struct thrift_if if_instance;
    GError *error = NULL; 
    if_open(&if_instance, hostname, port, &error);

    gchar *data;
    Response *Res;
    Res = g_object_new(TYPE_RESPONSE,NULL);

    if (!error && rpc_service_if_test(if_instance.client,&Res,input,&error)){   
            g_object_get (Res, "data", &data, NULL);
    }

   if_close(&if_instance, &error);

return 0;
} 

編譯：
gcc  client.c gen-c_glib/rpc_service.c gen-c_glib/sven_types.c -o client -lthrift_c_glib -lgobject-2.0

5. C程式碼中呼叫Go的客戶端

由於C的客戶端編譯依賴於thrift_c_glib與 gobject 動態庫，並且thrift_c_glib動態庫中對linux的一些系統庫又進行了引用，所以動態庫的依賴關係複雜，不利於在客戶端穩定、無依賴的部署。
可以採用使用Go編寫客戶端，然後編譯為.so檔案，供C程式呼叫。因為Go採用靜態原始碼編譯方式，可以無依賴的移植到各個伺服器中，在過程中需要注意C與Go基本資料結構之間的轉化。程式碼與go client的實現基本相同，只是go 與 C直接不允許 struct的傳遞，所以只能傳遞基本資料型別

/*client.go */

 package main

import (
    "./gen-go/thrift/rpc"
    "C"
    "fmt"
    "git.apache.org/thrift.git/lib/go/thrift"
    "net"
    "os"
)

/*  ！！！務必寫上"//export Test", 這不是註釋  ！！！*/
//export Test
func Test (input string, ip string, port string) *C.char {

    transportFactory := thrift.NewTFramedTransportFactory(thrift.NewTTransportFactory())
    protocolFactory := thrift.NewTBinaryProtocolFactoryDefault()

    tSocket, err := thrift.NewTSocket(net.JoinHostPort(ip, port))
    if err != nil {
        fmt.Fprintln(os.Stderr, "Error resolving address, ", err)
        os.Exit(1)
    }

    tTransport, _ := transportFactory.GetTransport(tSocket)
    client := rpc.NewRpcServiceClientFactory(tTransport, protocolFactory)
    if err := tTransport.Open(); err != nil {
        fmt.Fprintln(os.Stderr, (fmt.Errorf("Error opening socket to %s:%s : %v", ip, port, err)))
        os.Exit(1)
    }
    defer tTransport.Close()

    resp, _ := client.Test(input)

    return C.CString(resp.Data)
}

編譯為動態庫，執行下面命令會生成libclient.h 與 libclient.so兩個檔案。

go build -buildmode=c-shared -o libclient.so client.go

C 語言呼叫該 Go生成的動態庫：

#include <stdio.h>
#include "libclient.h"

int main()
{

    GoString input = {(char*)"test", 4};
    GoString ip = {(char*)"127.0.0.1", 9};
    GoString port = {(char*)"9090", 4};

    char *res = NULL;

    res = Test(input, ip, port);

    if (res != NULL)
    {
        printf("%s\n", res);
    }

    return 0;
}