Question

考虑以下两个过程：

sender.cpp：

#include <zhelpers.h>
...
zmq::context_t ctx(1);
...
void foo(int i)
{
   zmq::socket_t sender(ctx, ZMQ_REQ);
   sender.connect("tcp://hostname:5000");

   std::stringstream ss;
   ss <<"bar_" <<i;
   std::string bar_i(std::move(ss.str());

   s_sendmore(sender, "foo ");
   (i != N) ? s_send(sender, bar, 0) : s_send(sender, "done", 0);
   s_recv(sender);
}

int main()
{
    for(int i=0; i<=100000; ++i)
        foo(i);
    return 0;
}

receiver.cpp

#include <zhelpers.h>
...
int main()
{
    zmq::context_t ctx(1);
    zmq::socket_t rcv(ctx, ZMQ_REP);
    rcv.bind("tcp://*:5000");

    std::string s1("");
    std::string s2("");

    while(s2 != "done")
    {
        s1 = std::move(s_recv(rcv));
        s2 = std::move(s_recv(rcv));
        std::cout <<"received: " <<s1 <<" " <<s2 <<"\n";
        s_send(rcv, "ACK");
    }

    return 0;
}

让我们开始这两个过程。我期待的是，接收方进程将收到发件人发送给它的所有邮件，并打印出来：

foo bar_1
foo bar_2
...

等等，直到：

...
foo bar_100000

我希望它会毫无阻碍地完成这项工作。

我的问题是接收器始终坚持第28215次迭代（总是围绕这个数字!!!）并阻塞一分钟左右。然后它会进一步延伸到100000，但有时会再次粘住。我的问题当然是：为什么会发生这种情况？我该如何解决？

我试图将发件人放入＆＃39;在全局范围内的foo（。）内，然后它起作用：在这种情况下，所有打印输出从1到100000平稳且超快，没有任何阻塞（当然，在这种情况下，套接字不是每次都创建的foo（。）被称为）。但遗憾的是，在我的代码中，我无法做到这一点。

我想了解为什么会出现这种情况。

Answer 1

首先，您的示例不可靠，因为它们无法编译。所以这里有一些应该接近你的意图并实际编译的exapmles

sender.cpp

#include <zmq.hpp>
#include <string>
#include <iostream>
#include <string>

void send(const std::string& msg)
{
    //  Prepare our context and socket
    zmq::context_t context (1);
    zmq::socket_t socket (context, ZMQ_REQ);

    std::cout << "Connecting to receiver ..." << std::endl;
    socket.connect ("tcp://localhost:5555");

    zmq::message_t request (100);
    memcpy (request.data (), msg.c_str(), 100);
    std::cout << "Sending message " << msg << "..." << std::endl;
    socket.send (request);
}

int main ()
{
    for(int i = 0; i < 100000; ++i)
    {
        send(std::to_string(i));
    }
    send("done");
}

使用linke

g++ -std=c++11 -I/home/dev/cppzmq -I/home/dev/libzmq/include sender.cpp -lzmq -o sender

receiver.cpp

#include <zmq.hpp>
#include <string>
#include <cstring>
#include <iostream>

int main () {
    //  Prepare our context and socket
    zmq::context_t context (1);
    zmq::socket_t socket (context, ZMQ_REP);
    socket.bind ("tcp://*:5555");

    char buf[100] = {0};
    while (std::string(buf).compare("done")) {
        zmq::message_t request;

        //  Wait for next request from client
        socket.recv (&request);
        std::memcpy(buf, request.data(), 100);
        std::cout << "Received message " << buf << std::endl;

        //  Send reply back to client
        zmq::message_t reply (5);
        memcpy (reply.data (), "Hello", 5);
        socket.send (reply);
    }
    return 0;
}

使用

g++ -std=c++11 -I/home/dev/cppzmq -I/home/dev/libzmq/include receiver.cpp -lzmq -o receiver

启动进程时，一切似乎都正常，接收器上的输出正如预期的那样没有中断：

Received message 99996
Received message 99997
Received message 99998
Received message 99999
Received message done

但我的预期：看看netstat：

netstat
Active Internet connections (w/o servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State      
tcp        0      0 localhost:38345         localhost:5555          TIME_WAIT  
tcp        0      0 localhost:46228         localhost:5555          TIME_WAIT  
tcp        0      0 localhost:60309         localhost:5555          TIME_WAIT  
tcp        0      0 localhost:46916         localhost:5555          TIME_WAIT  
tcp        0      0 localhost:47600         localhost:5555          TIME_WAIT  
tcp        0      0 localhost:54454         localhost:5555          TIME_WAIT  
tcp        0      0 localhost:46409         localhost:5555          TIME_WAIT  
tcp        0      0 localhost:51142         localhost:5555          TIME_WAIT  
tcp        0      0 localhost:40355         localhost:5555          TIME_WAIT  
tcp        0      0 localhost:40005         localhost:5555          TIME_WAIT  
tcp        0      0 localhost:45614         localhost:5555          TIME_WAIT  
tcp        0      0 localhost:48974         localhost:5555          TIME_WAIT  
tcp        0      0 localhost:41427         localhost:5555          TIME_WAIT  
tcp        0      0 localhost:58740         localhost:5555          TIME_WAIT  
tcp        0      0 localhost:58754         localhost:5555          TIME_WAIT  
tcp        0      0 localhost:60044         localhost:5555          TIME_WAIT  
tcp        0      0 localhost:57478         localhost:5555          TIME_WAIT  
tcp        0      0 localhost:50419         localhost:5555          TIME_WAIT  
tcp        0      0 localhost:44361         localhost:5555          TIME_WAIT  
tcp        0      0 localhost:37284         localhost:5555          TIME_WAIT  
tcp        0      0 localhost:38662         localhost:5555          TIME_WAIT  
tcp        0      0 localhost:45968         localhost:5555          TIME_WAIT  
tcp        0      0 localhost:57407         localhost:5555          TIME_WAIT  
tcp        0      0 localhost:59200         localhost:5555          TIME_WAIT  
tcp        0      0 localhost:41292         localhost:5555          TIME_WAIT  
tcp        0      0 localhost:55243         localhost:5555          TIME_WAIT  
tcp        0      0 localhost:51489         localhost:5555          TIME_WAIT  
tcp        0      0 localhost:48865         localhost:5555          TIME_WAIT  
tcp        0      0 localhost:35491         localhost:5555          TIME_WAIT 
...

一次运行后，我在TIME_WAIT状态下有超过20k（！）这样的套接字。这是因为socket中void send(...)的{{1}}范围可变。我不确切知道zmq在超出范围时销毁套接字时的作用，但我很确定它会在套接字的fd上调用sender.cpp，这会使套接字处于TIME_WAIT状态。即使我的发送者和接收者运行顺利，我也不知道你的系统如何处理这么多的套接字。另外，我不知道你的close()文件是做什么的。但我知道如果将套接字放在全局范围内，则在一个套接字上只会在发送方进行一次close（）调用。我从这里开始调查更多。也许，看看how-to-forcibly-close-a-socket-in-time-wait ......

ZeroMQ REQ / REP性能

1 个答案: