SRS学习笔记5-SrsSignalManager分析

所在文件: app\srs_app_server.cpp,app\srs_app_server.hpp

SrsSignalManager* SrsSignalManager::instance = NULL;

SrsSignalManager::SrsSignalManager(SrsServer* server)
{
// 初始化成员变量
    SrsSignalManager::instance = this;
    
    _server = server;
    sig_pipe[0] = sig_pipe[1] = -1;
    pthread = new SrsEndlessThread("signal", this);
    signal_read_stfd = NULL;
}

SrsSignalManager::~SrsSignalManager()
{
// 关闭管道,释放资源
    srs_close_stfd(signal_read_stfd);
    
    if (sig_pipe[0] > 0) {
        ::close(sig_pipe[0]);
    }
    if (sig_pipe[1] > 0) {
        ::close(sig_pipe[1]);
    }
    
    srs_freep(pthread);
}

int SrsSignalManager::initialize()
{
    int ret = ERROR_SUCCESS;
    // 创建管道
    /* Create signal pipe */
    if (pipe(sig_pipe) < 0) {
        ret = ERROR_SYSTEM_CREATE_PIPE;
        srs_error("create signal manager pipe failed. ret=%d", ret);
        return ret;
    }
    //创建文件描述符对象
    if ((signal_read_stfd = st_netfd_open(sig_pipe[0])) == NULL) {
        ret = ERROR_SYSTEM_CREATE_PIPE;
        srs_error("create signal manage st pipe failed. ret=%d", ret);
        return ret;
    }
    
    return ret;
}

int SrsSignalManager::start()
{
    /**
    * Note that if multiple processes are used (see below), 
    * the signal pipe should be initialized after the fork(2) call 
    * so that each process has its own private pipe.
    */
    struct sigaction sa;
    
    /* Install sig_catcher() as a signal handler */
    sa.sa_handler = SrsSignalManager::sig_catcher;
    sigemptyset(&sa.sa_mask);
    sa.sa_flags = 0;
    sigaction(SIGNAL_RELOAD, &sa, NULL);
    
    sa.sa_handler = SrsSignalManager::sig_catcher;
    sigemptyset(&sa.sa_mask);
    sa.sa_flags = 0;
    sigaction(SIGTERM, &sa, NULL);
    
    sa.sa_handler = SrsSignalManager::sig_catcher;
    sigemptyset(&sa.sa_mask);
    sa.sa_flags = 0;
    sigaction(SIGINT, &sa, NULL);
    
    sa.sa_handler = SrsSignalManager::sig_catcher;
    sigemptyset(&sa.sa_mask);
    sa.sa_flags = 0;
    sigaction(SIGUSR2, &sa, NULL);
    
    srs_trace("signal installed");
    // 将 SrsSignalManager::sig_catcher设为信号处理函数,并启动信号处理线程
// 由于SrsSignalManager实现 ISrsEndlessThreadHandler接口,所在该线程的执行cycle函数

return pthread->start();
}

int SrsSignalManager::cycle()
{
//从管道读信号
    int ret = ERROR_SUCCESS;

    int signo;
    
    /* Read the next signal from the pipe */
    st_read(signal_read_stfd, &signo, sizeof(int), ST_UTIME_NO_TIMEOUT);
    
    /* Process signal synchronously */
    _server->on_signal(signo);
//由 SrsServer类的 on_signal函数来处理信号

return ret;
}

void SrsSignalManager::sig_catcher(int signo)
{
    int err;
    
    /* Save errno to restore it after the write() */
    err = errno;
    
    /* write() is reentrant/async-safe */
    int fd = SrsSignalManager::instance->sig_pipe[1];
    write(fd, &signo, sizeof(int));
    //向管道写信号
    errno = err;
}