进程池实现
本文是基于半同步/半异步进程池的实现，半同步/半异步模型主要是主进程监视listen套接字，然后发信号给子进程，子进程完成链接和读写数据。
本文实现的进程池特点：
1.使用epoll实现i/0复用；
2.实现信号和i/o事件的统一事件源。
3.使用管道进行子进程和父进程的通信。
代码如下：
#ifndef PROCESSPOOL_H
#define PROCESSPOOL_H
#include
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/*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:
process() : m_pid( -1 ){}
public:
pid_t m_pid;
int m_pipefd[2];
};
/*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:
/*将构造函数定义为私有的，因此我们只能通过后面的create静态函数来创建processpool实例*/
processpool( int listenfd, int process_number = 8 );
public:
/*单体模式，以保证程序最多创建一个processpool实例，这是程序正确处理信号的必要条件*/
static processpool< T >* create( int listenfd, int process_number = 8 )
{
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 = 16;
/*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*/
int m_idx;
/*每个进程都有一个epoll内核时间，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 = NULL;
/*用于处理信号的管道，以实现同意事件源。后面称之为信号管道*/
static int sig_pipefd[2];
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;
}
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内核时间表中删除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 );
}
/*信号处理函数*/
static void sig_handler( int sig )
{
int save_errno = errno;
int msg = sig;
send( sig_pipefd[1], ( char* )&msg, 1, 0 );
errno = save_errno;
}
/*设置信号处理函数*/
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，并建立它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 )
{
close( m_sub_process[i].m_pipefd[1] );
continue;
}
else
{
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 );
}
/*父进程中m_idx值为-1，子进程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piped，因为父进程将通过子进程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。我们直接使用connfd来索引逻辑处理对象（T类型的对象），
以提高程序效率*/
users[connfd].init( m_epollfd, connfd, client_address );
}
}
/*下面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;
}
}
}
}
}
else if( events[i].events & EPOLLIN )
{
users[sockfd].process();
}
else
{
continue;
}
}
}
delete [] users;
users = NULL;
close( pipefd );
//close( m_listenfd );
/*我们将上面这句话注释掉，以提醒读者：应该由m_listenfd的创建者来关闭这个文件描述符，
及所谓的“对象由哪个函数创建，就应该由哪个函数销毁”*/
close( m_epollfd );
}
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 )
{
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[sub_process_counter++].m_pipefd[0], ( char* )&new_conn, sizeof( new_conn ), 0 );
send( m_sub_process[i].m_pipefd[0], ( char* )&new_conn, sizeof( new_conn ), 0 );
printf( "send request to child %d\n", i );
//sub_process_counter %= m_process_number;
}
/*下面处理父进程接收到的信号*/
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 )
{
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:
{
/*如果父进程接收到终止信号，那么就杀死所有子进程，并等待它们全部结束。当然，通知子进程结束
更好的方法是向父、子进程之间的通信管道发送页数数据*/
printf( "kill all the clild now\n" );
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_listenfd );
/*由创建者关闭上面这个文件描述符*/
close( m_epollfd );
}
#endif