demon.cpp

Go to the documentation of this file.

/***************************************************************************
 *   Copyright (C) 2004-2006 by Ilya A. Volynets-Evenbakh                  *
 *   ilya@total-knowledge.com                                              *
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 *   This program is distributed in the hope that it will be useful,       *
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
 *   GNU General Public License for more details.                          *
 *                                                                         *
 *   You should have received a copy of the GNU General Public License     *
 *   along with this program; if not, write to the                         *
 *   Free Software Foundation, Inc.,                                       *
 *   59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.             *
 ***************************************************************************/
#include "demon.h"
#include <unistd.h>
#include <iostream>
#include <fcntl.h>
#include <sys/file.h>
#include <errno.h>
#include <stdio.h>
#include <stdexcept>
#include <string.h>
#include <stdlib.h>

namespace container {

Demon::Demon()
    : m_cinName("/dev/zero")
    , m_coutName("./servlet.log")
    , m_cerrName(m_coutName)
    , m_detach(false)
    , m_pidF(-1)
    , m_pidFPath("/var/run/cppserv.pid")
{
}


Demon::~Demon()
{
    if(m_pidF != -1) {
        ::flock(m_pidF,LOCK_UN);
        ::close(m_pidF);
        ::unlink(m_pidFPath.c_str());
    }
}


}


void container::Demon::start()
{
    int pid;
    if(m_detach){
        pid=fork();
        if(pid==-1) {
            std::string err("Error forking while detaching:");
            err += strerror(errno);
            throw std::runtime_error(err);
        }
        if(pid!=0) //Detached
            exit(0);
        // HACK ALERT! This may result in some problems with buffering!
        // This most likely does screw up system-level buffering options
        //std::cin.flush();
        std::cout.flush();
        std::cerr.flush();
        int cin=::open(m_cinName.c_str(),O_RDONLY|O_CREAT,S_IRUSR|S_IWUSR);
        if(cin == -1)std::cout<<"Unable to open CIN file ("<<m_cinName<<"): "<<strerror(errno)<<std::endl;
        int cout=::open(m_coutName.c_str(),O_WRONLY|O_CREAT|O_APPEND,S_IRUSR|S_IWUSR);
        if(cout == -1)std::cout<<"Unable to open COUT file ("<<m_coutName<<"): "<<strerror(errno)<<std::endl;
        int cerr=::open(m_cerrName.c_str(),O_WRONLY|O_CREAT|O_APPEND,S_IRUSR|S_IWUSR);
        if(cerr == -1)std::cout<<"Unable to open CIN file ("<<m_coutName<<"): "<<strerror(errno)<<std::endl;
        if(dup2(cin,0)==-1)std::cout<<"Couldn't reopen CIN! "<<errno<<':'<<strerror(errno)<<std::endl;
        if(dup2(cout,1)==-1)std::cout<<"Couldn't reopen COUT! "<<errno<<':'<<strerror(errno)<<std::endl;
        if(dup2(cerr,2)==-1)std::cout<<"Couldn't reopen CERR! "<<errno<<':'<<strerror(errno)<<std::endl;
        ::close(cin);
        ::close(cout);
        ::close(cerr);
        // Change session, to completely detach from controlling terminal
        ::setsid();
    }
    pid=getpid();
    m_pidF=::open(m_pidFPath.c_str(),O_RDWR|O_CREAT,S_IRUSR|S_IWUSR);
    if(m_pidF<0){
        std::cerr<<"Unable to open pid file: \""<<m_pidFPath<<"\": "<<strerror(errno)<<std::endl;
        return;
    }
    if(::flock(m_pidF,LOCK_EX|LOCK_NB)<0){
        std::cerr<<"Unable to lock pid file: \""<<m_pidFPath<<"\": "<<strerror(errno)<<std::endl;
        std::cerr<<"Is another cppserv already running?\n";
        return;
    }
    char buf[20];
    ::snprintf(buf,sizeof(buf)-1,"%d",pid);
    ::ftruncate(m_pidF,0);
    ::write(m_pidF,buf,strlen(buf));
    ::fsync(m_pidF);
    run();
}