daemonManager.py

# =======
# Imports
# =======

import sys, os
import jtvStreamsUpdater
import pprint
import subprocess

# =======
# Globals
# =======

PIDPATH = '/var/run'
PYPATH = sys.executable

RUNNING = 1
STARTED = 2
ALREADY_RUNNING = 3
NOT_RUNNING = 4
KILLED = 5

# ==========
# Exceptions
# ==========

class AlreadyStartedError(Exception):
    def __init__(self, pid):
        self.pid = pid

class NotRunningError(Exception):
    pass

# ===============
# Configure paths
# ===============

# Get the absolute path of this folder
FILEROOT = os.path.abspath(os.path.dirname(__file__))

# Set working directory to this
os.chdir(FILEROOT)

# ==========================
# Process handling functions
# ==========================

def startProcess(name, path):
    """
    Starts a process in the background and writes a PID file

    returns integer: pid
    """

    # Check if the process is already running
    status, pid = processStatus(name)

    if status == RUNNING:
        raise AlreadyStartedError(pid)

    # Start process
    command = (path).split(' ')
    process = subprocess.Popen(command, stdout='/dev/null', stderr='/dev/null')

    # Write PID file
    pidfilename = os.path.join(PIDPATH, name + '.pid')
    pidfile = open(pidfilename, 'w')
    pidfile.write(str(process.pid))
    pidfile.close()

    return process.pid

def stopProcess(name):
    """
    Stops a process started by startProcess

    returns integer: RESULT
    """

    # Get the status of the input process
    status, pid = processStatus(name)

    # If it's not running, return
    if status == NOT_RUNNING:
        return NOT_RUNNING

    # If it's running, kill it and remove the PID file
    os.system('kill %s > /dev/null 2> /dev/null' % pid)
    os.system('rm ' + os.path.join(PIDPATH, name + '.pid'))
    return KILLED

def processStatus(name):
    """
    Gets the status of a process started by startProcess

    returns tuple: ([RUNNING | NOT_RUNNING], pid)
    """

    pidfilename = os.path.join(PIDPATH, name + '.pid')

    # Try to open the PID file. If successfull, the process is running
    try:
        pidfile = open(pidfilename, 'r')
        pid = pidfile.read()
    except IOError as e:
        return (NOT_RUNNING, None)

    return (RUNNING, pid)

# ===================
# jtvDaemon functions
# ===================

def startjtv():
    """
    Starts the jtvStreamsUpdater loop in a background process

    returns tuple: (RESULT, pid)
    """

    # Check if process is already started
    status, pid = processStatus('jtvStreamUpdater')

    if status == RUNNING:
        return (ALREADY_RUNNING, pid)

    # Fork here
    pid = os.fork()

    # Write and return the child pid
    if pid:
        # Write PID to pid file
        pidfilepath = os.path.join(PIDPATH, 'jtvStreamsUpdater.pid')
        pidfile = open(pidfilepath, 'w')
        pidfile.write(str(pid))
        pidfile.close()

        return (STARTED, pid)

    # The child process should start the update loop
    else:
        # Don't output anything
        sys.stdout = open('/dev/null', 'w')

        from honsapp.jtvStreamsUpdater import mainUpdateLoop
        mainUpdateLoop()

def stopjtv():
    """
    Stops the jtvStreamsUpdater loop

    returns int: RESULT
    """

    # Try to kill the process
    return stopProcess('jtvStreamsUpdater')

# ================
# Script execution
# ================

if __name__ == '__main__':
    import argparse

    commands = ['startall', 'stopall',
                'startjtv', 'stopjtv', 'jtvstatus']

    help = """commands:
  startall    Starts all refreshing daemons
  stopall     Stops them

  startjtv    Starts the justin.tv streams refresher
  stopjtv     Stops it
  jtvstatus   Shows it's current status"""

    parser = argparse.ArgumentParser(epilog=help,
                           formatter_class=argparse.RawDescriptionHelpFormatter)

    # Add the main positional argument; command
    parser.add_argument('command', metavar='command', type=str,
                        choices=commands, help='The command to give the script')

    # Get the parser arguments
    args = parser.parse_args()

    # Abide the input command
    if args.command == 'startall':
        startallDaemons()

    elif args.command == 'stopall':
        stopallDaemons()

    elif args.command == 'startjtv':
        # Try to start the daemon
        result, pid = startjtv()

        if result == STARTED:
            print 'jtvStreamsUpdater started at ' + str(pid)
        elif result == ALREADY_RUNNING:
            print 'jtvStreamsUpdater already running at ' + str(pid)

    elif args.command == 'stopjtv':
        # Try to stop the daemon
        result = stopjtv()

        if result == KILLED:
            print 'jtvStreamsUpdater has been stopped'
        elif result == NOT_RUNNING:
            print 'jtvStreamsUpdater isn\'t running'

    elif args.command == 'jtvstatus':
        # Fetch the daemon status
        result, pid = processStatus('jtvStreamsUpdater')

        if result == RUNNING:
            print 'jtvStreamsUpdater is running at %s' % pid
        elif result == NOT_RUNNING:
            print 'jtvStreamsUpdater isn\'t running'