daemonextension.py

"""
Copyright (c) 2009, Sean Creeley
All rights reserved.

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are permitted provided that the following conditions are met:

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      list of conditions and the following disclaimer.
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      be used to endorse or promote products derived from this software without 
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=============
DaemonCommand
=============

Django Management Command for starting a daemon.

Use
===

Simple use of daemon command::

    from daemonextension import DaemonCommand
    from django.conf import settings
    import os
    
    class Command(DaemonCommand):
        
        stdout = os.path.join(settings.DIRNAME, "log/cubbyscott.out")
        stderr = os.path.join(settings.DIRNAME, "log/cubbyscott.err")
        pidfile = os.path.join(settings.DIRNAME, "pid/cb_link.pid")
        
        def handle_daemon(self, *args, **options):
            from flopsy import Connection, Consumer
            consumer = Consumer(connection=Connection())
            consumer.declare(queue='links', 
                             exchange='cubbyscott', 
                             routing_key='importer', auto_delete=False)
            
            def message_callback(message):
                print 'Recieved: ' + message.body
                consumer.channel.basic_ack(message.delivery_tag)
            
            consumer.register(message_callback)
            
            consumer.wait()

call::

    python python manage.py linkconsumer
    
"""

from django.core.management.base import BaseCommand
from optparse import make_option

import daemon
from daemon import pidlockfile

class DaemonCommand(BaseCommand):
        
    option_list = BaseCommand.option_list + (
        make_option('--chroot_directory', action='store', dest='chroot_directory',
            help='Full path to a directory to set as the effective root directory of \
            the process.'),
        make_option('--working_directory', action='store', dest='working_directory',
            default="/",
            help='Full path of the working directory to which the process should \
            change on daemon start.'),
        make_option('--umask', action='store', dest='umask', default=0, type="int",
            help='File access creation mask ("umask") to set for the process on \
            daemon start.'),
        make_option('--pidfile', action='store', dest='pidfile',
            help='Context manager for a PID lock file. When the daemon context opens \
            and closes, it enters and exits the `pidfile` context manager.'),
        make_option('--detach_process', action='store', dest='detach_process', 
            help='If ``True``, detach the process context when opening the daemon \
            context; if ``False``, do not detach.'),
        make_option('--uid', action='store', dest='uid', 
            help='The user ID ("UID") value to switch the process to on daemon start.'),
        make_option('--gid', action='store', dest='gid', 
            help='The group ID ("GID") value to switch the process to on daemon start.'),
        make_option('--prevent_core', action='store', dest='prevent_core', default=True,
            help='If true, prevents the generation of core files, in order to avoid \
            leaking sensitive information from daemons run as `root`.'),
        make_option('--stdin', action='store', dest='stdin', 
            help='Standard In'),
        make_option('--stdout', action='store', dest='stdout',
            help='Standard Out'),
        make_option('--stderr', action='store', dest='stderr',
            help='Standard Error'),
    )
    help = 'Create a daemon'
    
    chroot_directory = None
    working_directory = '/'
    umask = 0
    detach_process = True
    prevent_core = True
    stdin = None
    stdout = None
    stderr = None
    pidfile = None
    uid = None
    gid = None    
    
    
    def get_option_value(self, options, name, expected=None):
        value = options.get(name)
        if value == expected:
            value = getattr(self, name)
        print name, ' ', value
        return value
    
    def handle(self, *args, **options):
        """
        Takes the options and starts a daemon context from them. 
        
        Example::
        
            python manage.py linkconsumer --pidfile=/var/run/cb_link.pid 
                --stdout=/var/log/cb/links.out --stderr=/var/log/cb/links.err
        
        """
        context = daemon.DaemonContext()
        
        context.chroot_directory = self.get_option_value(options, 'chroot_directory')
        context.working_directory = self.get_option_value(options, 'working_directory', '/')
        context.umask = self.get_option_value(options, 'umask', 0)
        context.detach_process = self.get_option_value(options, 'detach_process')
        context.prevent_core = self.get_option_value(options, 'prevent_core', True)
        
        #Get file objects
        stdin =  self.get_option_value(options, 'stdin')
        if stdin is not None:
            context.stdin = open(stdin, "r")
        
        stdout = self.get_option_value(options, 'stdout')
        if stdout is not None:
            context.stdout = open(stdout, "a+")
        
        stderr = self.get_option_value(options, 'stderr')
        if stderr is not None:
            context.stderr = open(stderr, "a+")  
        
        #Make pid lock file
        pidfile = self.get_option_value(options, 'pidfile')
        if pidfile is not None:
            context.pidfile=pidlockfile.PIDLockFile(pidfile)
        
        uid = self.get_option_value(options, 'uid')
        if uid is not None:
            context.uid = uid
        
        gid = self.get_option_value(options, 'gid')
        if gid is not None:
            context.gid = uid
        
        context.open()        
        
        self.handle_daemon(*args, **options)

    def handle_daemon(self, *args, **options):
        """
        Perform the command's actions in the given daemon context
        """
        raise NotImplementedError()