libevent带负载均衡的多线程使用示例

from http://blog.chinaunix.net/uid-756931-id-353318.html

分类： LINUX

功能： 主线程根据负载工作线程负载均衡算法，每隔一秒钟向特定的工作线程发送一条字符串信息，工作线程简单的把字符串信息打开出来。
Makefile

1. eventtest : eventtest.c
2. gcc -Wall -g -levent -lpthread -o eventtest eventtest.c
3. .PHONY : clean
4. clean :
5. rm eventtest -f

eventtest.c

    #include <stdio.h>
    #include <stdlib.h>
    #include <unistd.h>
    #include <pthread.h>

    #include <sys/types.h>
    #include <sys/socket.h>

    #include <event.h>


    typedef struct {
        pthread_t tid;
        struct event_base *base;
        struct event event;
        int read_fd;
        int write_fd;
    }LIBEVENT_THREAD;

    typedef struct {
        pthread_t tid;
        struct event_base *base;
    }DISPATCHER_THREAD;


    const int thread_num = 10;

    LIBEVENT_THREAD *threads;
    DISPATCHER_THREAD dispatcher_thread;
    int last_thread = 0;



    static void
    thread_libevent_process(int fd, short which, void *arg)
    {
        int ret;
        char buf[128];
        LIBEVENT_THREAD *me = arg;

        if (fd != me->read_fd) {
            printf("thread_libevent_process error : fd != me->read_fd\n");
            exit(1);
        }

        ret = read(fd, buf, 128);
        if (ret > 0) {
            buf[ret] = '\0';
            printf("thread %llu receive message : %s\n", (unsigned long long)me->tid, buf);
        }


        return;
    }

    static void *
    worker_thread(void *arg)
    {
        LIBEVENT_THREAD *me = arg;
        me->tid = pthread_self();

        event_base_loop(me->base, 0);


        return NULL;
    }

    static void
    timeout_cb(int fd, short event, void *arg)
    {
        struct timeval tv;
        struct event *timeout = arg;

        int tid = (last_thread + 1) % thread_num;        //memcached中线程负载均衡算法

        LIBEVENT_THREAD *thread = threads + tid;

        last_thread = tid;

        write(thread->write_fd, "Hello world!", sizeof("Hello world!") - 1);

        evutil_timerclear(&tv);
        tv.tv_sec = 1;
        event_add(timeout, &tv);
    }

    int
    main (int argc, char *argv[])
    {
        int ret;
        int i;
        int fd[2];
        struct event timeout;
        struct timeval tv;

        pthread_t tid;

        dispatcher_thread.base = event_init();
        if (dispatcher_thread.base == NULL) {
            perror("event_init( base )");
            return 1;
        }
        dispatcher_thread.tid = pthread_self();


        threads = calloc(thread_num, sizeof(LIBEVENT_THREAD));
        if (threads == NULL) {
            perror("calloc");
            return 1;
        }

        for (i = 0; i < thread_num; i++) {

            ret = socketpair(AF_LOCAL, SOCK_STREAM, 0, fd);
            if (ret == -1) {
                perror("socketpair()");
                return 1;
            }

            threads[i].read_fd = fd[1];
            threads[i].write_fd = fd[0];

            threads[i].base = event_init();
            if (threads[i].base == NULL) {
                perror("event_init()");
                return 1;
            }


            event_set(&threads[i].event, threads[i].read_fd, EV_READ | EV_PERSIST, thread_libevent_process, &threads[i]);
            event_base_set(threads[i].base, &threads[i].event);
            if (event_add(&threads[i].event, 0) == -1) {
                perror("event_add()");
                return 1;
            }
        }

        for (i = 0; i < thread_num; i++) {
            pthread_create(&tid, NULL, worker_thread, &threads[i]);
        }

        evtimer_set(&timeout, timeout_cb, &timeout);
        event_base_set(dispatcher_thread.base, &timeout);
        evutil_timerclear(&tv);
        tv.tv_sec = 1;
        event_add(&timeout, &tv);

        event_base_loop(dispatcher_thread.base, 0);


        return 0;
    }