daemon.py

#!/usr/bin/env python

import sys, os, time, atexit
from signal import SIGTERM 

class Daemon:
    """
    A generic daemon class.    
    Usage: subclass the Daemon class and override the run() method
    """
    '''
    Modified by Tread Soft for yowsup-daemon.  
    '''
    def __init__(self, pidfile, out):
        path=os.getcwd()
        self.stdin = 'dev/null'
        if out==True:
            self.stdout =os.getcwd()+'/out' 
        else:
            self.stdout='dev/null'
        self.stderr = os.getcwd()+'/err.log'
        self.pidfile = pidfile
    
    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:
                # exit first parent
                sys.exit(0) 
        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("/") 
        os.setsid() 
        os.umask(0) 
    
        # 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) 
    
        # redirect standard file descriptors
        sys.stdout.flush()
        sys.stderr.flush()
        si = open(self.stdin, 'r')
        so = open(self.stdout, 'a+')
        se = open(self.stderr, 'a+', 1)
        os.dup2(si.fileno(), sys.stdin.fileno())
        os.dup2(so.fileno(), sys.stdout.fileno())
        os.dup2(se.fileno(), sys.stderr.fileno())
    
        # write pidfile
        atexit.register(self.delpid)
        pid = str(os.getpid())
        open(self.pidfile,'w+').write("%s\n" % pid)
    
    def delpid(self):
        os.remove(self.pidfile)
    def status(self):

        try:
            pf=open(self.pidfile,'r')
            pid=int(pf.read().strip())
            pf.close()
        except IOError:
            pid=None
        
        if pid:
            message="Daemon running\n"
            sys.stderr.write(message )
            sys.exit(1)
        else:
            message="Daemon not running\n"
            sys.stderr.write(message )
            sys.exit(1)

    def start(self):
        """
        Start the daemon
        """
        # Check for a pidfile to see if the daemon already runs
        
        try:
            pf = open(self.pidfile,'r')
            pid = int(pf.read().strip())
            pf.close()

        except IOError:
            pid = None
        
        if pid:
            message = "Pidfile %s already exists. Daemon already running?\n"
            sys.stderr.write(message % self.pidfile)
            sys.exit(1)
        
        # Start the daemon
        print ("Daemon starting. Check output in out and errors in err.log")
        self.daemonize()
        self.run()
    def nodaemon(self):
        self.run()
    def stop(self):
        """
        Stop the daemon
        """
        # Get the pid from the pidfile
        try:
            pf = open(self.pidfile,'r')
            pid = int(pf.read().strip())
            pf.close()
            print ("Daemon stopped.")
        except IOError:
            pid = None
    
        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:
            while 1:
                os.kill(pid, SIGTERM)
                time.sleep(0.1)
        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)

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

    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().
        """