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Well behaved unix daemons for every occasion.

Project description

Well behaved unix daemons for every occasion.

What Is Daemons?

Daemons is a resource library for Python developers that want to create daemon processes. The classes in this library provide the basic daemonization, signal handling, and pid management functionality while allowing for any implementation of behaviour and logic.

Example Custom Daemon

import time

from daemons.prefab import run

class SleepyDaemon(run.RunDaemon):

    def run(self):

        while True:

            time.sleep(1)

Now to create a simple init script which can launch the daemon.

#!/usr/bin/env python

import logging
import os
import sys
import time

from mypackage import SleepyDaemon


if __name__ == '__main__':

    action = sys.argv[1]
    logfile = os.path.join(os.getcwd(), "sleepy.log")
    pidfile = os.path.join(os.getcwd(), "sleepy.pid")

    logging.basicConfig(filename=logfile, level=logging.DEBUG)
    d = SleepyDaemon(pidfile=pidfile)

    if action == "start":

        d.start()

    elif action == "stop":

        d.stop()

    elif action == "restart":

        d.restart()

There are more daemon types than the simple RunDaemon. Check the docs for more.

Wrapping Existing Code

Daemons can also be used to daemonize an arbitrary Python function.

import time

from daemons import daemonizer

@daemonizer.run(pidfile="/tmp/sleepy.pid")
def sleepy(sleep_time):

    while True:

        time.sleep(sleep_time)

sleep(20)  # Daemon started with 20 second sleep time.

The daemonizer also supports adding signal handlers. Check the docs for more.

Daemon Functionality

The daemons in the ‘prefab’ module come bundled with the following features:

  • pidfile management
  • signal handling
  • start/stop/restart functionality
  • unix process daemonization

The default implementation of these feature are all driven by Python standard library modules. Each component may be overridden or extended by adding another base class to your daemon that implements the component interface. Check the ‘interfaces’ package for items to implement.

The ‘prefab’ daemons come in three flavors. The ‘RunDaemon’ requires that you implement the ‘run’ method which should use some form of a loop. If the ‘run’ method completes the process will stop. The ‘StepDaemon’ requires that you implement the ‘step’ method. The process will call ‘step’ on an infinite loop. The eventlet and gevent message daemons require that you implement the ‘get_message’ and ‘handle_message’ methods. These will fetch and handle messages within green-threads.

License

Copyright 2013 Kevin Conway

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

   http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.

Contributing

All contributions to this project are protected under the agreement found in the CONTRIBUTING file. All contributors should read the agreement but, as a summary:

You give us the rights to maintain and distribute your code and we promise
to maintain an open source distribution of anything you contribute.

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