libevent带负载均衡的多线程使用示例

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

eventtest : eventtest.c
gcc -Wall -g -levent -lpthread -o eventtest eventtest.c
.PHONY : clean
clean :
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;
}