利用libevent 和线程池实现高并发服务器的设计

主进程添加监听套接字的事件并进行事件循环，将连接描述符放入定义的数据结构中，并在主进程中进行写管道，触发子线程的读管道事件，然后从连接结构中获取连接描述符进行和客户端进行通信。其中主进程和子线程都有不同的基事件base.

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

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

#include <event.h>
#include <queue>
#include <iostream>

#include <arpa/inet.h>

#include <memory.h>

const int thread_num = 10;
#define BUF_SIZE 1024

using namespace std;

typedef struct {
pthread_t tid;
struct event_base *base;
struct event event;
int read_fd;
int write_fd;
//queue<int> q;
int f_connect;
char * buffer;
}LIBEVENT_THREAD;                 //需要保存的信息结构，用于管道通信和基事件的管理

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

LIBEVENT_THREAD *threads = (LIBEVENT_THREAD *) calloc(thread_num, sizeof(LIBEVENT_THREAD));

void on_write(int sock, short event, void* arg);

void on_read(int sock, short event, void* arg)
{

cout<<"on_read() called, sock="<<sock<<endl;
if(NULL == arg){
return;
}
LIBEVENT_THREAD* event_thread = (LIBEVENT_THREAD*) arg;//获取传进来的参数
char* buffer = new char[BUF_SIZE];
memset(buffer, 0, sizeof(char)*BUF_SIZE);
//--本来应该用while一直循环，但由于用了libevent，只在可以读的时候才触发on_read(),故不必用while了
int size = read(sock, buffer, BUF_SIZE);
if(0 == size){//说明socket关闭
cout<<"read size is 0 for socket:"<<sock<<endl;
//  destroy_sock_ev(event_struct);

//event_thread->q.pop();
close(sock);
return;
}
cout<<"i have receive: "<<buffer<<endl;

event_thread->buffer=buffer;

struct event* write_ev = (struct event*)malloc(sizeof(struct event));//发生写事件（也就是只要socket缓冲区可写）时，就将反馈数据通过socket写回客户端
event_set(write_ev, sock, EV_WRITE, on_write, event_thread);

event_base_set(event_thread->base, write_ev);
event_add(write_ev, NULL);
cout<<"on_read() finished, sock="<<sock<<endl;

}

void on_write(int sock, short event, void* arg)
{

if(NULL == arg){
return;
}
LIBEVENT_THREAD* event_write_thread = (LIBEVENT_THREAD*) arg;//获取传进来的参数
//char* buffer = new char[BUF_SIZE];
//memset(buffer, 0, sizeof(char)*BUF_SIZE);

//strcpy(buffer,event_write_thread->buffer,sizeof(event_write_thread->buffer));
//--本来应该用while一直循环，但由于用了libevent，只在可以读的时候才触发on_read(),故不必用while了
write(sock, event_write_thread->buffer, BUF_SIZE);

free(event_write_thread->buffer);

event_write_thread->buffer=NULL;

}

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

int fdconnect;

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);

}

cout<<"thread_libevent_process\n"<<endl;

/*if(me->q.size()>0)
{
fdconnect=me->q.front();
me->q.pop();

ret = read(fd, buf, 128);
if (ret > 0)
{

buf[ret] = '\0';

printf("thread %llu receive message : %s\n", (unsigned long long)me->tid, buf);

}
}*/

/*if(me->q.size()>0)
{
fdconnect=me->q.front();

cout<<"thread_libevent_process succeed "<<endl;
//me->q.pop();
}

else
return ;*/

fdconnect=me->f_connect;

struct event* read_ev = (struct event*)malloc(sizeof(struct event));//发生读事件后，从socket中取出数据

event_set(read_ev, fdconnect, EV_READ|EV_PERSIST, on_read, me);

event_base_set(me->base, read_ev);

event_add(read_ev, NULL);

return;
}

void thread_init()
{
int ret;
int fd[2];
for (int i = 0; i < thread_num; i++) {

ret = socketpair(AF_LOCAL, SOCK_STREAM, 0, fd);

if (ret == -1) {
perror("socketpair()");
return  ;
}

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

threads[i].base = event_init();

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

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 ;
}

cout<<"thread_init succeed"<<endl;

}
}

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

//event_base_loop(me->base, 0);

event_base_dispatch(me->base);//每个工作线程都在检测event链表是否有事件发生

return NULL;
}

void CreatPhreadPool()
{

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

cout<<"CreatPhreadPool"<<endl;
}

int getSocket(){
int fd =socket( AF_INET, SOCK_STREAM, 0 );
if(-1 == fd){
cout<<"Error, fd is -1"<<endl;
}
return fd;
}

int last_thread=0;

void event_handler(int sock, short event, void* arg)  //添加其他信息

{
struct sockaddr_in remote_addr;
int sin_size=sizeof(struct sockaddr_in);
int new_fd = accept(sock,  (struct sockaddr*) &remote_addr, (socklen_t*)&sin_size);    //如果线程池已用完，怎么办呢？
if(new_fd < 0){
cout<<"Accept error in on_accept()"<<endl;
return;
}
cout<<"new_fd accepted is "<<new_fd<<endl;

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;

thread->f_connect=new_fd;

write(thread->write_fd, " ", 1);

cout<<"on_accept() finished for fd="<<new_fd<<endl;
}

DISPATCHER_THREAD dispatcher_thread;        //用于设置主线程的结构变量

int main(int argc, char** argv)
{

thread_init();

CreatPhreadPool();

int fd_listen = getSocket();
if(fd_listen <0){
cout<<"Error in main(), fd<0"<<endl;
}
//cout<<"main() fd="<<fd<<endl;
//----为服务器主线程绑定ip和port------------------------------
struct sockaddr_in local_addr; //服务器端网络地址结构体
memset(&local_addr,0,sizeof(local_addr)); //数据初始化--清零
local_addr.sin_family=AF_INET; //设置为IP通信
local_addr.sin_addr.s_addr=inet_addr(argv[1]);//服务器IP地址
local_addr.sin_port=htons(atoi(argv[2])); //服务器端口号
int bind_result = bind(fd_listen, (struct sockaddr*) &local_addr, sizeof(struct sockaddr));
if(bind_result < 0){
cout<<"Bind Error in main()"<<endl;
return -1;
}
cout<<"bind_result="<<bind_result<<endl;
listen(fd_listen, 10);

evutil_make_socket_nonblocking(fd);
//-----设置libevent事件，每当socket出现可读事件，就调用on_accept()------------
struct event_base* base = event_base_new();
dispatcher_thread.base=base;
dispatcher_thread.tid = pthread_self();

struct event listen_ev;
event_set(&listen_ev, fd_listen, EV_READ|EV_PERSIST, event_handler, NULL);
event_base_set(dispatcher_thread.base, &listen_ev);
event_add(&listen_ev, NULL);
event_base_dispatch(dispatcher_thread.base);//监听线程
//------以下语句理论上是不会走到的---------------------------
cout<<"event_base_dispatch() in main() finished"<<endl;
//----销毁资源-------------
event_del(&listen_ev);
event_base_free(dispatcher_thread.base);
cout<<"main() finished"<<endl;

}

![这是设计服务器的框图]

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