libevent带负载均衡的多线程使用示例

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

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;

}