python 守护进程

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其实早在2007年的时候 国外的大佬已经实现了 

A simple unix/linux daemon in Python – Lone Wolves – Web, game, and open source development

 自己基本上没有做改动 直接搬到自己的项目中 很好用  比 nohup ./program &  好用多了！！

#!/usr/bin/env python

import sys, os, time, atexit, platform, traceback, logging,signal

class Daemon:
    """
    A generic daemon class.
    
    Usage: subclass the Daemon class and override the run() method
    """
    def __init__(self, pidfile, stdin=os.devnull, stdout=os.devnull, stderr=os.devnull,home_dir='.',umask=0,verbose=1):
        self.stdin = stdin   #标准输入 例如键盘输入
        self.stdout = stdout    #标准输出 命令窗口输出
        self.stderr = stderr    #标准出错
        self.pidfile = pidfile  #pid文件绝对路径  
        self.home_dir = home_dir    #主目录 根目录
        self.umask = umask  #文件权限设置掩码
        self.verbose = verbose  #调试开关
        self.daemon_alive = True    #进程是否在运行
    
    def daemonize(self):
        """
        do the UNIX double-fork magic, see Stevens' "Advanced 
        Programming in the UNIX Environment" for details (ISBN 0201563177)
        http://www.erlenstar.demon.co.uk/unix/faq_2.html#SEC16
        """
        try: 
            pid = os.fork() 
            if pid > 0: #正常fork后 为0 否则fork没有成功
                # exit first parent
                sys.exit(0) #无错误 退出
        except OSError as e: 
            sys.stderr.write("fork #1 failed: %d (%s)\n" % (e.errno, e.strerror))
            sys.exit(1)
    
        # decouple from parent environment
        os.chdir(self.home_dir) #换到根目录
        os.setsid() #获得独立进程号
        os.umask(self.umask)#设置文件权限掩码  
        # do second fork
        try: 
            pid = os.fork() 
            if pid > 0:
                # exit from second parent
                sys.exit(0) 
        except OSError as e: 
            sys.stderr.write("fork #2 failed: %d (%s)\n" % (e.errno, e.strerror))
            sys.exit(1) 
        if sys.platform != 'darwin':
            # This block breaks on OS X 
            # redirect standard file descriptors
            sys.stdout.flush() #清除标准输入
            sys.stderr.flush()  #清除错误信息
            si = open(self.stdin, 'r') #打开标准输入
            so = open(self.stdout, 'a+') #打开标准输出  
            if self.stderr:#如果有自定义的出错输出
                se = open(self.stderr, 'ab+', 0)
            else:
                se = so
            os.dup2(si.fileno(), sys.stdin.fileno()) #os.dup2(fd,fd2)将一个文件描述符 fd 复制到另一个 fd2。
            os.dup2(so.fileno(), sys.stdout.fileno())
            os.dup2(se.fileno(), sys.stderr.fileno())
        def sig_handler(signum, frame):  
            self.daemon_alive = False  
        # 注册信号处理程序
        signal.signal(signal.SIGTERM, sig_handler)  
        signal.signal(signal.SIGINT, sig_handler) 

        if self.verbose >= 1:  
            print('daemon process started ...')
        # write pidfile
        atexit.register(self.delpid)
        pid = str(os.getpid())
        #file(self.pidfile, 'w+').write("%s\n" % pid)
        with open(self.pidfile,"w+") as f:
            f.write("%s\n" % pid)
    
    def delpid(self):
        os.remove(self.pidfile)


    def get_pid(self):
        try:
            pf = open(self.pidfile, 'r')
            pid = int(pf.read().strip())
            pf.close()
        except IOError:
            pid = None
        except SystemExit:
            pid = None
        return pid

    def start(self):
        """
        Start the daemon
        """
        # Check for a pidfile to see if the daemon already runs
        if self.verbose >= 1:  
            print('ready to starting ......')
        pid = self.get_pid()
        if pid:
            message = "pidfile %s already exist. Daemon already running?\n"
            sys.stderr.write(message % self.pidfile)
            sys.exit(1)
        
        # Start the daemon
        self.daemonize()
        self.run()

    def stop(self):
        """
        Stop the daemon
        """
        # Get the pid from the pidfile
        if self.verbose >= 1:  
            print('stopping ...')
        pid = self.get_pid()
    
        if not pid:
            message = "pidfile %s does not exist. Daemon not running?\n"
            sys.stderr.write(message % self.pidfile)
            return  # not an error in a restart

        # Try killing the daemon process    
        try:
            i = 0
            while 1:
                os.kill(pid, signal.SIGTERM)
                time.sleep(0.1)
                i = i + 1
                if i % 10 == 0:
                    os.kill(pid,signal.SIGHUP)
        except OSError as err:
            err = str(err)
            if err.find("No such process") > 0:
                if os.path.exists(self.pidfile):
                    os.remove(self.pidfile)
            else:
                print(str(err))
                sys.exit(1)
            if self.verbose >= 1:  
                print('Stopped!')

    def restart(self):
        """
        Restart the daemon
        """
        self.stop()
        self.start()

    def is_running(self):
        pid = self.get_pid()
        return pid and os.path.exists('/proc/%d' % pid)

    def run(self):
        """
        You should override this method when you subclass Daemon. It will be called after the process has been
        daemonized by start() or restart().
        """

class MyDaemon(Daemon):
    def __init__(self,pidpath, func):
        Daemon.__init__(self, pidpath)
        self.__func = func
    def run(self):
        self.__func(True)

        
def log_uncaught_exceptions(ex_cls, ex, tb):
    logging.critical(''.join(traceback.format_tb(tb)))
    logging.critical('{0}: {1}'.format(ex_cls, ex))

def run(pidpath,func):
    sys.excepthook = log_uncaught_exceptions
    if platform.system() == "Linux":
        daemon = MyDaemon(pidpath,func)
        if len(sys.argv) >= 2:
            if 'start' == sys.argv[1]:
                daemon.start()
            elif 'stop' == sys.argv[1]:
                daemon.stop()
            elif 'restart' == sys.argv[1]:
                daemon.restart()
            elif 'console' == sys.argv[1]:
                func(False)    
            elif 'status' == sys.argv[1]:
                alive = daemon.is_running()
                if alive:
                    print('process [%s] is running ......' % daemon.get_pid())
                else:
                    print('daemon process stopped')
            else:
                print("Unknown command")
                sys.exit(2)
            sys.exit(0)
        else:
            print("usage:python %s start|stop|restart|console" % sys.argv[0])
            sys.exit(2)
    else:
        func(False)

def daemonFunc(isdaemon):
    serverStart()
    reactor.run()
    serverStop()

def run():
    daemon.run(pidpath, daemonFunc)

if __name__ == "__main__":
    run()