多进程服务器中,epoll的创建应该在创建子进程之后

转：http://blog.csdn.net/wei801004/archive/2009/06/13/4264031.aspx

看我的测试代码,似乎应该是在创建子进程之后创建epoll的fd,否则程序将会有问题,试将代码中两个CreateWorker函数的调用位置分别调用,一个在创建epoll fd之前,一个在之后,在调用在创建之前的代码会出问题,在我的机器上(linux内核2.6.26)表现的症状就是所有进程的epoll_wait函数返回0, 而客户端似乎被阻塞了:

服务器端:

 

#include <iostream>
#include <sys/socket.h>
#include <sys/epoll.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdio.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/wait.h>
using namespace std;
#define MAXLINE 5
#define OPEN_MAX 100
#define LISTENQ 20
#define SERV_PORT 5000
#define INFTIM 1000
typedef struct task_t
{
    int fd;
    char buffer[100];
    int n;
}task_t;
int CreateWorker(int nWorker)
{
    if (0 < nWorker)
    {
        bool bIsChild;
        pid_t nPid;
        while (!bIsChild)
        {
            if (0 < nWorker)
            {
                nPid = ::fork();
                if (nPid > 0)
                {
                    bIsChild = false;
                    --nWorker;
                }
                else if (0 == nPid)
                {
                    bIsChild = true;
                    printf("create worker %d success!/n", ::getpid());
                }
                else
                {
                    printf("fork error: %s/n", ::strerror(errno));
                    return -1;
                }
            }
            else
            {
                int nStatus;
                if (-1 == ::wait(&nStatus))
                {
                    ++nWorker;
                }
            }
        }
    }
    return 0;
}
void setnonblocking(int sock)
{
    int opts;
    opts=fcntl(sock,F_GETFL);
    if(opts<0)
    {
        perror("fcntl(sock,GETFL)");
        exit(1);
    }
    opts = opts|O_NONBLOCK;
    if(fcntl(sock,F_SETFL,opts)<0)
    {
        perror("fcntl(sock,SETFL,opts)");
        exit(1);
    }
}
int main()
{
    int i, maxi, listenfd, connfd, sockfd,epfd,nfds;
    ssize_t n;
    char line[MAXLINE];
    socklen_t clilen;
    struct epoll_event ev,events[20];
    struct sockaddr_in clientaddr;
    struct sockaddr_in serveraddr;
    listenfd = socket(AF_INET, SOCK_STREAM, 0);
       bzero(&serveraddr, sizeof(serveraddr));
    serveraddr.sin_family = AF_INET;
    char *local_addr="127.0.0.1";
    inet_aton(local_addr,&(serveraddr.sin_addr));//htons(SERV_PORT);
    serveraddr.sin_port=htons(SERV_PORT);
      // 地址重用
    int nOptVal = 1;
    socklen_t nOptLen = sizeof(int);
    if (-1 == ::setsockopt(listenfd, SOL_SOCKET, SO_REUSEADDR, &nOptVal, nOptLen))
    {
        return -1;
    }
    setnonblocking(listenfd);
    bind(listenfd,(sockaddr *)&serveraddr, sizeof(serveraddr));
    listen(listenfd, LISTENQ);

    CreateWorker(5);

    //把socket设置为非阻塞方式

    //生成用于处理accept的epoll专用的文件描述符
    epfd=epoll_create(256);
    //设置与要处理的事件相关的文件描述符
    ev.data.fd=listenfd;
    //设置要处理的事件类型
    ev.events=EPOLLIN|EPOLLET;
    //ev.events=EPOLLIN;
    //注册epoll事件
    epoll_ctl(epfd,EPOLL_CTL_ADD,listenfd,&ev);

     //CreateWorker(5);

    maxi = 0;

    task_t task;
    task_t *ptask;
    while(true)
    {
        //等待epoll事件的发生
        nfds=epoll_wait(epfd,events,20,500);
        //处理所发生的所有事件
        for(i=0;i<nfds;++i)
        {
            if(events[i].data.fd==listenfd)
            {
                connfd = accept(listenfd,NULL, NULL);
                if(connfd<0){
                    printf("connfd<0, listenfd = %d/n", listenfd);
                    printf("error = %s/n", strerror(errno));
                    exit(1);
                }
                setnonblocking(connfd);

                //设置用于读操作的文件描述符
                memset(&task, 0, sizeof(task));
                task.fd = connfd;
                ev.data.ptr = &task;
                //设置用于注册的读操作事件
                ev.events=EPOLLIN|EPOLLET;
                //ev.events=EPOLLIN;
                //注册ev
                epoll_ctl(epfd,EPOLL_CTL_ADD,connfd,&ev);
            }
            else if(events[i].events&EPOLLIN)
            {
                cout << "EPOLLIN" << endl;
                ptask = (task_t*)events[i].data.ptr;
                sockfd = ptask->fd;

                if ( (ptask->n = read(sockfd, ptask->buffer, 100)) < 0) {
                    if (errno == ECONNRESET) {
                        close(sockfd);
                        events[i].data.ptr = NULL;
                    } else
                        std::cout<<"readline error"<<std::endl;
                } else if (ptask->n == 0) {
                    close(sockfd);
                    events[i].data.ptr = NULL;
                }
                ptask->buffer[ptask->n] = '/0';
                cout << "read " << ptask->buffer << endl;

                //设置用于写操作的文件描述符
                ev.data.ptr = ptask;
                //设置用于注测的写操作事件
                ev.events=EPOLLOUT|EPOLLET;

                //修改sockfd上要处理的事件为EPOLLOUT
                epoll_ctl(epfd,EPOLL_CTL_MOD,sockfd,&ev);
            }
            else if(events[i].events&EPOLLOUT)
            {
                cout << "EPOLLOUT" << endl;
                ptask = (task_t*)events[i].data.ptr;
                sockfd = ptask->fd;

                write(sockfd, ptask->buffer, ptask->n);

                //设置用于读操作的文件描述符
                ev.data.ptr = ptask;

                //修改sockfd上要处理的事件为EPOLIN
                epoll_ctl(epfd,EPOLL_CTL_DEL,sockfd,&ev);
                cout << "write " << ptask->buffer;
                memset(ptask, 0, sizeof(*ptask));
                close(sockfd);
            }
        }
    }
    return 0;
}

 

测试客户端:

 

#!/usr/bin/perl
use strict;
use Socket;
use IO::Handle;
sub echoclient
{
    my $host = "127.0.0.1";
    my $port = 5000;
    my $protocol = getprotobyname("TCP");
    $host = inet_aton($host);
    socket(SOCK, AF_INET, SOCK_STREAM, $protocol) or die "socket() failed: $!";
    my $dest_addr = sockaddr_in($port, $host);
    connect(SOCK, $dest_addr) or die "connect() failed: $!";
    SOCK->autoflush(1);
    my $msg_out = "hello world/n";
    print "out = ", $msg_out;
    print SOCK $msg_out;
    my $msg_in = <SOCK>;
    print "in = ", $msg_in;
    close SOCK;
}
#&echoclient;
#exit(0);
for (my $i = 0; $i < 9999; $i++)
{
    echoclient;
}

 lighttpd 也是在创建完子进程后创建的epoll的fd.