zeromq学习记录(八)负载均衡 附ZMQ_ROUTER的流程分析

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ROUTER 与 REQ通讯

#include "stdafx.h"
#include "zhelpers.hpp"
#include <thread>

void worker_thread(void *arg) {
    zmq::context_t context();
    zmq::socket_t worker(context, ZMQ_REQ);

    s_set_id(worker, (intptr_t)arg);
    worker.connect("tcp://localhost:5671"); // "ipc" doesn't yet work on windows.

    int total = ;
    while () {
        //  Tell the broker we're ready for work
        s_send(worker, "Hi Boss");

        //  Get workload from broker, until finished
        std::string workload = s_recv(worker);
        if ("Fired!" == workload) {
            std::cout << "Processed: " << total << " tasks" << std::endl;
            break;
        }
        total++;

        //  Do some random work
        s_sleep(within() + );
    }
    return;
}

int main() {
    zmq::context_t context();
    zmq::socket_t broker(context, ZMQ_ROUTER);

    broker.bind("tcp://*:5671"); // "ipc" doesn't yet work on windows.

    const int NBR_WORKERS = ;
    std::thread workers[NBR_WORKERS];
    for (int worker_nbr = ; worker_nbr < NBR_WORKERS; worker_nbr++) {
        workers[worker_nbr]= std::thread( worker_thread, (void *)(intptr_t)worker_nbr);
    }

    //  Run for five seconds and then tell workers to end
    int64_t end_time = s_clock() + ;
    int workers_fired = ;
    while () {
        //  Next message gives us least recently used worker
        std::string identity = s_recv(broker);
        s_recv(broker);     //  Envelope delimiter
        s_recv(broker);     //  Response from worker       

        s_sendmore(broker, identity);
        s_sendmore(broker, "");
        //  Encourage workers until it's time to fire them
        if (s_clock() < end_time)
            s_send(broker, "Work harder");
        else {
            s_send(broker, "Fired!");
            if (++workers_fired == NBR_WORKERS)
                break;
        }
    }

    for (int worker_nbr = ; worker_nbr < NBR_WORKERS; worker_nbr++) {
        workers[worker_nbr].join();
    }
    return ;
}

ROUTER 与 DEALER通讯

// rtdealer_cpp.cpp : 定义控制台应用程序的入口点。
//

#include "stdafx.h"
//
//  Custom routing Router to Dealer
//
// Olivier Chamoux <olivier.chamoux@fr.thalesgroup.com>

#include "zhelpers.hpp"
#include <thread>

static void *
worker_task(void *args)
{
    zmq::context_t context();
    zmq::socket_t worker(context, ZMQ_DEALER);

#if (defined (WIN32))
    s_set_id(worker, (intptr_t)args);
#else
    s_set_id(worker);          //  Set a printable identity
#endif

    worker.connect("tcp://localhost:5671");

    int total = ;
    while () {
        //  Tell the broker we're ready for work
        s_sendmore(worker, "");
        s_send(worker, "Hi Boss");

        //  Get workload from broker, until finished
        s_recv(worker);     //  Envelope delimiter
        std::string workload = s_recv(worker);
        //  .skip
        if ("Fired!" == workload) {
            std::cout << "Completed: " << total << " tasks" << std::endl;
            break;
        }
        total++;

        //  Do some random work
        s_sleep(within() + );
    }

    return NULL;
}

//  .split main task
//  While this example runs in a single process, that is just to make
//  it easier to start and stop the example. Each thread has its own
//  context and conceptually acts as a separate process.
int main() {
    zmq::context_t context();
    zmq::socket_t broker(context, ZMQ_ROUTER);

    broker.bind("tcp://*:5671");
    srandom((unsigned)time(NULL));

    const int NBR_WORKERS = ;
    std::thread workers[NBR_WORKERS];
    int worker_nbr = ;
    for (; worker_nbr < NBR_WORKERS; ++worker_nbr) {
        workers[worker_nbr] = std::thread( worker_task, (void *)(intptr_t)worker_nbr);
    }

    //  Run for five seconds and then tell workers to end
    int64_t end_time = s_clock() + ;
    int workers_fired = ;
    while () {
        //  Next message gives us least recently used worker
        std::string identity = s_recv(broker);
        {
            s_recv(broker);     //  Envelope delimiter
            s_recv(broker);     //  Response from worker
        }

        s_sendmore(broker, identity);
        s_sendmore(broker, "");

        //  Encourage workers until it's time to fire them
        if (s_clock() < end_time)
            s_send(broker, "Work harder");
        else {
            s_send(broker, "Fired!");
            if (++workers_fired == NBR_WORKERS)
                break;
        }
    }

    for (int worker_nbr = ; worker_nbr < NBR_WORKERS; ++worker_nbr) {
        workers[worker_nbr].join();
    }

    return ;
}

DEALER REQ区别在于 REQ模式socket发送信息时候会自动在信息前添加“”空白信息作为隔离

DEALER模式socket需要手动添加 s_sendmore(socket, "");

而ROUTER 在接受信息前会受到来源socket的地址信息 而发送时会将地址信息添加到socket的信息之前 同时还要在在信息前添加“”空白信息作为隔离

s_sendmore(broker, identity);
s_sendmore(broker, "");

均衡负载 此段代码比较复杂 理解较难

我将代码设置为单线程 然后调试 纠正了一些我理解的router模式

稍后画图

// lbbroker_cpp.cpp : 定义控制台应用程序的入口点。
//

#include "stdafx.h"
#include "zhelpers.hpp"
#include <thread>
#include <queue>

void client_thread(void* arg) {
    zmq::context_t context();
    zmq::socket_t client(context, ZMQ_REQ);

    s_set_id(client, (intptr_t));
    client.connect("tcp://localhost:5672");

    s_send(client, "HELLO");
    std::string reply = s_recv(client);
    std::cout << "Client: " << reply << std::endl;
    return;
}

void worker_thread(void* arg){
    zmq::context_t context();
    zmq::socket_t worker(context, ZMQ_REQ);

    s_set_id(worker, (intptr_t));
    worker.connect("tcp://localhost:5673");

    s_send(worker, "READY");
    while () {
        std::string address = s_recv(worker);
        {
            std::string empty = s_recv(worker);
            assert(empty.size() == );
        }
        std::string request = s_recv(worker);
        std::cout << "Worker: " << request << std::endl;

        s_sendmore(worker, address);
        s_sendmore(worker, "");
        s_send(worker, "OK");
    }
    return;
}

int main()
{
    zmq::context_t context();
    zmq::socket_t frontend(context, ZMQ_ROUTER);
    zmq::socket_t backend(context, ZMQ_ROUTER);

    frontend.bind("tcp://*:5672");
    backend.bind("tcp://*:5673");

    int client_nbr;
    std::thread client[];
    for (client_nbr = ; client_nbr < ; client_nbr++)
    {
        client[client_nbr] = std::thread(client_thread,(void *)(intptr_t)client_nbr);
    }

    int worker_nbr;
    std::thread worker[];
    for (worker_nbr = ; worker_nbr < ; worker_nbr++)
    {
        worker[worker_nbr] = std::thread(worker_thread, (void *)(intptr_t)worker_nbr);
    }

    std::queue<std::string> worker_queue;

    while ()
    {
        zmq::pollitem_t items[] = {
            {backend,,ZMQ_POLLIN,},
            {frontend,,ZMQ_POLLIN,}
        };
        if (worker_queue.size())
            zmq::poll(&items[], , -);
        else
            zmq::poll(&items[], , -);

        if (items[].revents & ZMQ_POLLIN) {

            //  Queue worker address for LRU routing
            worker_queue.push(s_recv(backend));

            {
                //  Second frame is empty
                std::string empty = s_recv(backend);
                assert(empty.size() == );
            }

            //  Third frame is READY or else a client reply address
            std::string client_addr = s_recv(backend);

            //  If client reply, send rest back to frontend
            if (client_addr.compare("READY") != ) {

                {
                    std::string empty = s_recv(backend);
                    assert(empty.size() == );
                }

                std::string reply = s_recv(backend);
                s_sendmore(frontend, client_addr);
                s_sendmore(frontend, "");
                s_send(frontend, reply);

                if (--client_nbr == )
                    break;
            }
        }
        if (items[].revents & ZMQ_POLLIN) {

            //  Now get next client request, route to LRU worker
            //  Client request is [address][empty][request]
            std::string client_addr = s_recv(frontend);

            {
                std::string empty = s_recv(frontend);
                assert(empty.size() == );
            }

            std::string request = s_recv(frontend);

            std::string worker_addr = worker_queue.front();//worker_queue [0];
            worker_queue.pop();

            s_sendmore(backend, worker_addr);
            s_sendmore(backend, "");
            s_sendmore(backend, client_addr);
            s_sendmore(backend, "");
            s_send(backend, request);
        }
    }

    for (client_nbr = ; client_nbr < ; client_nbr++)
    {
        client[client_nbr].join();
    }

    for (worker_nbr = ; worker_nbr < ; worker_nbr++)
    {
        worker[worker_nbr].join();
    }

    return ;
}

此处图仅为个人领悟 不能保证完全正确 请谨慎参考

开始看官方的图示 我以为上述代码是如官方所示

但是对于router来说

connect到router的客户端或者工作者(client worker)

与router直接send到router的信息处理上是有区别的

下图用直线和箭头来区分

我将代码设置为单线程 然后调试 得出流程如图:

由于新建线程的随机性

步骤1 2 是的先后次序是随机的

1 client 发送信息到frontend router

信息格式为

"0001"

""

"HELLO"

2 worker发送信息到backend router

信息格式为

"0009"

""

"READY"

3函数主体进入POLL循环

根据代码

if (worker_queue.size())
zmq::poll(&items[0], 2, -1);
else
zmq::poll(&items[0], 1, -1);

由于空闲worker队列中暂时无记录

所以仅仅对backend 进行poll轮询

首先接受信息记录的通讯ID 为9 并push进worker队列

worker_queue.push(s_recv(backend));

然后接受空字节分隔符 在接受发送的正文“READY”

接收信息格式如下:

"0009"

""

"READY"

由于此次接受的正文是“READY” 根据代码不进入发送流程

if (client_addr.compare("READY") != 0)

步骤3结束

4 主体代码进入第二次POLL轮询

frontend 接收信息如下

信息格式为

"0001"

""

"HELLO"

弹出之前接收空闲worker的ID

std::string worker_addr = worker_queue.front();

然后向backend发送信息格式如下:

"0009"

""

"0001"

""

"HELLO"

5 backend接收信息后直接路由到ID为0009的worker

6 worker接收到信息格式为

"0001"

""

"HELLO"

然后发送信息格式:

"0001"

""

"OK"

7 backend接收到步骤6的信息：

将步骤6的worker的id 0009 push仅worker队列

worker_queue.push(s_recv(backend));

此次接受的信息格式为

"0009"

""

"001"

""

"OK"

由于此次接受正文不是"READY"

进入发送模式 发送信息到frontend

发送信息格式为

"0001"

""

"OK"

8 frontend直接路由此信息到ID 0001的client

最后client接收到的信息格式为

"OK"