app/django/utils/daemonize.py
author Sverre Rabbelier <srabbelier@gmail.com>
Sun, 19 Apr 2009 17:42:44 +0000
changeset 2246 c29272f640b0
parent 323 ff1a9aa48cfd
permissions -rw-r--r--
Tweak the 'load balancing' algorithm In order to reduce contention we randomly skipped jobs, but this caused many jobs to end up stopping early. Now instead we keep on going until we time out (also increased the chance of doing work). Patch by: Sverre Rabbelier

import os
import sys

if os.name == 'posix':
    def become_daemon(our_home_dir='.', out_log='/dev/null',
                      err_log='/dev/null', umask=022):
        "Robustly turn into a UNIX daemon, running in our_home_dir."
        # First fork
        try:
            if os.fork() > 0:
                sys.exit(0)     # kill off parent
        except OSError, e:
            sys.stderr.write("fork #1 failed: (%d) %s\n" % (e.errno, e.strerror))
            sys.exit(1)
        os.setsid()
        os.chdir(our_home_dir)
        os.umask(umask)

        # Second fork
        try:
            if os.fork() > 0:
                os._exit(0)
        except OSError, e:
            sys.stderr.write("fork #2 failed: (%d) %s\n" % (e.errno, e.strerror))
            os._exit(1)

        si = open('/dev/null', 'r')
        so = open(out_log, 'a+', 0)
        se = open(err_log, 'a+', 0)
        os.dup2(si.fileno(), sys.stdin.fileno())
        os.dup2(so.fileno(), sys.stdout.fileno())
        os.dup2(se.fileno(), sys.stderr.fileno())
        # Set custom file descriptors so that they get proper buffering.
        sys.stdout, sys.stderr = so, se
else:
    def become_daemon(our_home_dir='.', out_log=None, err_log=None, umask=022):
        """
        If we're not running under a POSIX system, just simulate the daemon
        mode by doing redirections and directory changing.
        """
        os.chdir(our_home_dir)
        os.umask(umask)
        sys.stdin.close()
        sys.stdout.close()
        sys.stderr.close()
        if err_log:
            sys.stderr = open(err_log, 'a', 0)
        else:
            sys.stderr = NullDevice()
        if out_log:
            sys.stdout = open(out_log, 'a', 0)
        else:
            sys.stdout = NullDevice()

    class NullDevice:
        "A writeable object that writes to nowhere -- like /dev/null."
        def write(self, s):
            pass