processpool.h

#ifndef PROCESSPOOL_H
#define PROCESSPOOL_H

#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <assert.h>
#include <stdio.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <fcntl.h>
#include <stdlib.h>
#include <sys/epoll.h>
#include <signal.h>
#include <sys/wait.h>
#include <sys/stat.h>

/* 描述一个子进程的类，m_pid是目标子进程的PID, m_pipefd是父进程和子进程通信用的管道 */
class Process
{
public:
    pid_t m_pid;
    int m_pipefd[2];
    Process() : m_pid(-1) {}
};
/* 进程池类，将它定义为模板类是为了代码复用。其模板参数是处理逻辑任务的类 */
template <typename T>
class Processpool
{
private:
    //单例模式
    Processpool(int listenfd, int process_number = 4);

public:
    static Processpool<T> *create(int listenfd, int process_number = 4)
    {
        if (!m_instance)
        {
            m_instance = new Processpool<T>(listenfd, process_number);
        }
        return m_instance;
    }

    ~Processpool()
    {
        delete[] m_sub_process;
    }

    //启动进程池
    void run();

private:
    void setup_sig_pipe();
    void run_parent();
    void run_child();

private:
    // 进程池允许的最大子进程数量
    static const int MAX_PROCESS_NUMBER = 8;
    // 每个子进程最多能处理的客户数量
    static const int USER_PER_PROCESS = 65536;
    // epoll最多能处理的事件数
    static const int MAX_EVENT_NUMBER = 10000;
    //进程池中的进程总数
    int m_process_number;
    //子进程在池中的序号，从0开始, 当m_idx=-1代表父进程
    int m_idx;
    //每个进程都有一个epoll内核事件表，用m_epollfd标识
    int m_epollfd;
    //监听socket
    int m_listenfd;
    //子进程通过m_stop来决定是否停止运行
    int m_stop;
    //保存所有子进程的描述信息
    Process *m_sub_process;
    //进程池静态实例
    static Processpool<T> *m_instance;
};
template<typename T>
Processpool<T> * Processpool<T>::m_instance = nullptr;

//用于处理信号的管道，以实现统一事件源。
static int sig_pipefd[2];

//将文件描述符设置为非阻塞，返回旧描述符信息
static int setnonblocking(int fd)
{
    int old_option = fcntl(fd, F_GETFL);
    int new_option = old_option | O_NONBLOCK;
    fcntl(fd, F_SETFL, new_option);
    return old_option;
}

//将fd注册到epoll事件集中，采用ET边缘触发模式
static void addfd(int epollfd, int fd)
{
    epoll_event event;
    event.data.fd = fd;
    event.events = EPOLLIN | EPOLLET;
    epoll_ctl(epollfd, EPOLL_CTL_ADD, fd, &event);
    setnonblocking(fd);
}

//从epollfd标识的epoll内核事件表中删除fd上的所有注册事件
static void removefd(int epollfd, int fd)
{
    epoll_ctl(epollfd, EPOLL_CTL_DEL, fd, 0);
    close(fd);
}
//信号处理回调函数
static void sig_handler(int sig)
{
    //保留原来的errno，在函数最后恢复，以保证函数的可重入性
    int save_errno = errno;
    int msg = sig;
    send(sig_pipefd[1], (char *)&msg, 1, 0);
    errno = save_errno;
}

static void addsig(int sig, void(handler)(int), bool restart = true)
{
    struct sigaction sa;
    memset(&sa, '\0', sizeof(sa));
    sa.sa_handler = handler;
    if (restart)
    {
        sa.sa_flags |= SA_RESTART;
    }
    sigfillset(&sa.sa_mask);
    assert(sigaction(sig, &sa, NULL) != -1);
}

//进程池构造函数。参数listenfd是监听socket，它必须在创建进程池之前被创建，否则子进程无法直接引用它。参数process_number指定进程池中子进程的数量
template <typename T>
Processpool<T>::Processpool(int listenfd, int process_number) : m_listenfd(listenfd), m_process_number(process_number), m_idx(-1), m_stop(false)
{
    assert((process_number > 0) && (process_number <= MAX_PROCESS_NUMBER));
    m_sub_process = new Process[process_number];
    assert(m_sub_process);
    //创建process_number个子进程，并建立他们和父进程之间的管道
    for (int i = 0; i < process_number; i++)
    {
        int ret = socketpair(PF_UNIX, SOCK_STREAM, 0, m_sub_process[i].m_pipefd);
        assert(ret == 0);
        m_sub_process[i].m_pid = fork();
        assert(m_sub_process[i].m_pid >= 0);
        if (m_sub_process[i].m_pid > 0) //父进程继续生成子进程
        {
            close(m_sub_process[i].m_pipefd[1]);
            continue;
        }
        else //子进程执行的代码块，子进程不再生成自己的子进程，所以break
        {
            close(m_sub_process[i].m_pipefd[0]);
            m_idx = i;
            break;
        }
    }
}

//统一事件源
template <typename T>
void Processpool<T>::setup_sig_pipe()
{
    //创建epoll事件监听表和信号管道
    m_epollfd = epoll_create(5);
    assert(m_epollfd != -1);
    int ret = socketpair(PF_UNIX, SOCK_STREAM, 0, sig_pipefd);
    assert(ret != -1);
    setnonblocking(sig_pipefd[1]);
    addfd(m_epollfd, sig_pipefd[0]);

    //设置信号处理函数
    addsig(SIGCHLD, sig_handler);
    addsig(SIGTERM, sig_handler);
    addsig(SIGINT, sig_handler);
    addsig(SIGPIPE, SIG_IGN); //SIG_IGN信号忽略
}
//父进程中m_idx值为-1，子进程中m_idx值大于等于0， 我们据此判断接下来要运行的是父进程代码还是子进程代码
template <typename T>
void Processpool<T>::run()
{
    if (m_idx != -1)
    {
        run_child();
        return;
    }
    run_parent();
}

template <typename T>
void Processpool<T>::run_child()
{
    setup_sig_pipe();
    //每个子进程都通过其在进程池中的序号值m_idx找到与父进程通信的管道
    int pipefd = m_sub_process[m_idx].m_pipefd[1];
    //子进程需要监听管道文件描述符pipefd，因为父进程将通过它来通知子进程accept新连接
    addfd(m_epollfd, pipefd);

    epoll_event events[MAX_EVENT_NUMBER];
    T *users = new T[USER_PER_PROCESS];
    assert(users);
    int number = 0;
    int ret = -1;
    while (!m_stop)
    {
        number = epoll_wait(m_epollfd, events, MAX_EVENT_NUMBER, -1);
        if ((number < 0) && (errno != EINTR))
        {
            printf("epoll failure\n");
            break;
        }

        for (int i = 0; i < number; i++)
        {
            int sockfd = events[i].data.fd;
            if ((sockfd == pipefd) && (events[i].events & EPOLLIN))
            {
                int client = 0;
                //从父子进程之间的管道读取数据，并将结果保存在变量client中，如果读取成功，则表示有新客户连接到来
                ret = recv(sockfd, (char *)&client, sizeof(client), 0);
                if (((ret < 0) && (errno != EAGAIN)) || ret == 0)
                    continue;
                else
                {
                    struct sockaddr_in client_address;
                    socklen_t client_addrlength = sizeof(client_address);
                    int connfd = accept(m_listenfd, (struct sockaddr *)&client_address, &client_addrlength);
                    if (connfd < 0)
                    {
                        printf("errno is : %d\n", errno);
                        continue;
                    }
                    addfd(m_epollfd, connfd);
                    //模板类T必须实现init方法，以初始化一个客户连接
                    users[connfd].init(m_epollfd, connfd, client_address);
                }
            }
            //处理子进程接收到的信号
            else if ((sockfd == sig_pipefd[0]) && (events[i].events & EPOLLIN))
            {
                int sig;
                char signals[1024];
                ret = recv(sig_pipefd[0], signals, sizeof(signals), 0);
                if (ret <= 0)
                    continue;
                else
                {
                    for (int i = 0; i < ret; i++)
                    {
                        switch (signals[i])
                        {
                        case SIGCHLD:
                            pid_t pid;
                            int stat;
                            while ((pid = waitpid(-1, &stat, WNOHANG)) > 0)
                            {
                                continue;
                            }
                            break;
                        case SIGTERM:
                        case SIGINT:
                            m_stop = true;
                            break;
                        default:
                            break;
                        }
                    }
                }
            }
            //如果是其他可读数据，那么必然是客户请求到来，调用逻辑处理对象的process方法处理之
            else if (events[i].events & EPOLLIN)
            {
                users[sockfd].process();
            }
            else
                continue;
        }
    }
    delete[] users;
    users = nullptr;
    close(pipefd);
}

template <typename T>
void Processpool<T>::run_parent()
{
    setup_sig_pipe();
    //父进程监听m_listenfd
    addfd(m_epollfd, m_listenfd);
    epoll_event events[MAX_EVENT_NUMBER];
    int sub_process_counter = 0;
    int new_conn = 1;
    int number = 0;
    int ret = -1;

    while (!m_stop)
    {
        number = epoll_wait(m_epollfd, events, MAX_EVENT_NUMBER, -1);
        if ((number < 0) && (errno != EINTR))
        {
            printf("epoll failure\n");
            break;
        }
        for (int i = 0; i < number; i++)
        {
            int sockfd = events[i].data.fd;
            if (sockfd == m_listenfd)
            {
                //如果有新连接到来，就采用Round Robin方式将其分配给一个子进程处理
                int i = sub_process_counter;
                do
                {
                    if (m_sub_process[i].m_pid != -1)
                    {
                        break;
                    }
                    i = (i + 1) % m_process_number;
                } while (i != sub_process_counter);
                if (m_sub_process[i].m_pid == -1)
                {
                    m_stop = true;
                    break;
                }
                sub_process_counter = (i + 1) % m_process_number;
                send(m_sub_process[i].m_pipefd[0], (char *)&new_conn, sizeof(new_conn), 0);
                printf("send request to child %d\n", i);
            }
            else if ((sockfd == sig_pipefd[0]) && (events[i].events & EPOLLIN))
            {
                int sig;
                char signals[1024];
                ret = recv(sig_pipefd[0], signals, sizeof(signals), 0);
                if (ret <= 0)
                    continue;
                else
                {
                    for (int i = 0; i < ret; i++)
                    {
                        switch (signals[i])
                        {
                        case SIGCHLD:
                            pid_t pid;
                            int stat;
                            while ((pid = waitpid(-1, &stat, WNOHANG)) > 0)
                            {
                                for (int i = 0; i < m_process_number; i++)
                                {
                                    //如果进程池中第i个子进程退出了，则主进程关闭相应的通信管道，并设置相应的m_pid为-1， 以标记该子进程已经退出
                                    if (m_sub_process[i].m_pid == pid)
                                    {
                                        printf("child %d join\n", i);
                                        close(m_sub_process[i].m_pipefd[0]);
                                        m_sub_process[i].m_pid = -1;
                                    }
                                }
                            }
                            m_stop = true;
                            for (int i = 0; i < m_process_number; i++)
                            {
                                if (m_sub_process[i].m_pid != -1)
                                {
                                    m_stop = false;
                                }
                            }
                            break;
                        case SIGTERM:
                        case SIGINT:
                            for (int i = 0; i < m_process_number; i++)
                            {
                                int pid = m_sub_process[i].m_pid;
                                if (pid != -1)
                                {
                                    kill(pid, SIGTERM);
                                }
                            }
                            break;
                        default:
                            break;
                        }
                    }
                }
            }
            else
                continue;
        }
    }
    close(m_epollfd);
}

#endif