Synnefo

#!/usr/bin/env python

# Copyright 2011 GRNET S.A. All rights reserved.

#

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# THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND

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# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE

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""" Message queue setup, dispatch and admin

This program sets up connections to the queues configured in settings.py

and implements the message wait and dispatch loops. Actual messages are

handled in the dispatched functions.

"""

from django.core.management import setup_environ

import sys

import os

path = os.path.normpath(os.path.join(os.getcwd(), '..'))

sys.path.append(path)

import synnefo.settings as settings

from synnefo.logic import log

setup_environ(settings)

from amqplib import client_0_8 as amqp

from signal import signal, SIGINT, SIGTERM

import time

import socket

from daemon import daemon

# Take care of differences between python-daemon versions.

try:

    from daemon import pidfile

except:

    from daemon import pidlockfile

from synnefo.logic import callbacks

class Dispatcher:

    logger = None

    chan = None

    debug = False

    clienttags = []

    def __init__(self, debug = False):

        # Initialize logger

        self.logger = log.get_logger('synnefo.dispatcher')

        self.debug = debug

        self._init()

    def wait(self):

        while True:

            try:

                self.chan.wait()

            except SystemExit:

                break

            except amqp.exceptions.AMQPConnectionException:

                self.logger.error("Server went away, reconnecting...")

                self._init()

            except socket.error:

                self.logger.error("Server went away, reconnecting...")

                self._init()

        [self.chan.basic_cancel(clienttag) for clienttag in self.clienttags]

        self.chan.connection.close()

        self.chan.close()

    def _init(self):

        self.logger.info("Initializing")

        # Connect to RabbitMQ

        conn = None

        while conn == None:

            self.logger.info("Attempting to connect to %s",

                             settings.RABBIT_HOST)

            try:

                conn = amqp.Connection(host=settings.RABBIT_HOST,

                                       userid=settings.RABBIT_USERNAME,

                                       password=settings.RABBIT_PASSWORD,

                                       virtual_host=settings.RABBIT_VHOST)

            except socket.error:

                time.sleep(1)

        self.logger.info("Connection succesful, opening channel")

        self.chan = conn.channel()

        # Declare queues and exchanges

        for exchange in settings.EXCHANGES:

            self.chan.exchange_declare(exchange=exchange, type="topic",

                                       durable=True, auto_delete=False)

        for queue in settings.QUEUES:

            self.chan.queue_declare(queue=queue, durable=True,

                                    exclusive=False, auto_delete=False)

        bindings = settings.BINDINGS

        # Special queue for debugging, should not appear in production

        if self.debug:

            self.chan.queue_declare(queue=settings.QUEUE_DEBUG, durable=True,

                                    exclusive=False, auto_delete=False)

            bindings += settings.BINDINGS_DEBUG

        # Bind queues to handler methods

        for binding in bindings:

            try:

                callback = getattr(callbacks, binding[3])

            except AttributeError:

                self.logger.error("Cannot find callback %s" % binding[3])

                continue

            self.chan.queue_bind(queue=binding[0], exchange=binding[1],

                                 routing_key=binding[2])

            tag = self.chan.basic_consume(queue=binding[0], callback=callback)

            self.logger.debug("Binding %s(%s) to queue %s with handler %s" %

                              (binding[1], binding[2], binding[0], binding[3]))

            self.clienttags.append(tag)

def _exit_handler(signum, frame):

    """"Catch exit signal in children processes."""

    print "%d: Caught signal %d, will raise SystemExit" % (os.getpid(), signum)

    raise SystemExit

def _parent_handler(signum, frame):

    """"Catch exit signal in parent process and forward it to children."""

    global children

    print "Caught signal %d, sending kill signal to children" % signum

    [os.kill(pid, SIGTERM) for pid in children]

def child(cmdline):

    """The context of the child process"""

    # Cmd line argument parsing

    (opts, args) = parse_arguments(cmdline)

    disp = Dispatcher(debug = opts.debug)

    # Start the event loop

    disp.wait()

def parse_arguments(args):

    from optparse import OptionParser

    parser = OptionParser()

    parser.add_option("-d", "--debug", action="store_true", default=False,

                      dest="debug", help="Enable debug mode")

    parser.add_option("-w", "--workers", default=2, dest="workers",

                      help="Number of workers to spawn", type="int")

    parser.add_option("-p", '--pid-file', dest="pid_file",

                      default=os.path.join(os.getcwd(), "dispatcher.pid"),

                      help="Save PID to file (default:%s)" %

                           os.path.join(os.getcwd(), "dispatcher.pid"))

    parser.add_option("--purge-queues", action="store_true",

                      default=False, dest="purge_queues",

                      help="Remove all declared queues (DANGEROUS!)")

    parser.add_option("--purge-exchanges", action="store_true",

                      default=False, dest="purge_exchanges",

                      help="Remove all exchanges. Implies deleting all queues \

                           first (DANGEROUS!)")

    parser.add_option("--drain-queue", dest="drain_queue",

                      help="Strips a queue from all outstanding messages")

    return parser.parse_args(args)

def purge_queues() :

    """

        Delete declared queues from RabbitMQ. Use with care!

    """

    conn = get_connection()

    chan = conn.channel()

    print "Queues to be deleted: ",  settings.QUEUES

    if not get_user_confirmation():

        return

    for queue in settings.QUEUES:

        try:

            chan.queue_delete(queue=queue)

            print "Deleting queue %s" % queue

        except amqp.exceptions.AMQPChannelException as e:

            print e.amqp_reply_code, " ", e.amqp_reply_text

            chan = conn.channel()

    chan.connection.close()

def purge_exchanges():

    """

        Delete declared exchanges from RabbitMQ, after removing all queues first

    """

    purge_queues()

    conn = get_connection()

    chan = conn.channel()

    print "Exchnages to be deleted: ", settings.EXCHANGES

    if not get_user_confirmation():

        return

    for exchange in settings.EXCHANGES:

        try:

            chan.exchange_delete(exchange=exchange)

        except amqp.exceptions.AMQPChannelException as e:

            print e.amqp_reply_code, " ", e.amqp_reply_text

    chan.connection.close()

def drain_queue(queue):

    """

        Strip a (declared) queue from all outstanding messages

    """

    if not queue:

        return

    if not queue in settings.QUEUES:

        print "Queue %s not configured" % queue

        return

    print "Queue to be drained: %s" % queue

    if not get_user_confirmation():

        return

    conn = get_connection()

    chan = conn.channel()

    # Register a temporary queue binding

    for binding in settings.BINDINGS:

        if binding[0] == queue:

            exch = binding[1]

    if not exch:

        print "Queue not bound to any exchange: %s" % queue

        return

    chan.queue_bind(queue=queue, exchange=exch,routing_key='#')

    tag = chan.basic_consume(queue=queue, callback=callbacks.dummy_proc)

    print "Queue draining about to start, hit Ctrl+c when done"

    time.sleep(2)

    print "Queue draining starting"

    signal(SIGTERM, _exit_handler)

    signal(SIGINT, _exit_handler)

    while True:

        chan.wait()

    chan.basic_cancel(tag)

    chan.connection.close()

def get_connection():

    conn = amqp.Connection( host=settings.RABBIT_HOST,

                        userid=settings.RABBIT_USERNAME,

                        password=settings.RABBIT_PASSWORD,

                        virtual_host=settings.RABBIT_VHOST)

    return conn

def get_user_confirmation():

    ans = raw_input("Are you sure (N/y):")

    if not ans:

        return False

    if ans not in ['Y', 'y']:

        return False

    return True

def debug_mode():

    disp = Dispatcher(debug = True)

    signal(SIGINT, _exit_handler)

    signal(SIGTERM, _exit_handler)

    disp.wait()

def main():

    global children, logger

    (opts, args) = parse_arguments(sys.argv[1:])

    logger = log.get_logger("synnefo.dispatcher")

    # Special case for the clean up queues action

    if opts.purge_queues:

        purge_queues()

        return

    # Special case for the clean up exch action

    if opts.purge_exchanges:

        purge_exchanges()

        return

    if opts.drain_queue:

        drain_queue(opts.drain_queue)

        return

    # Debug mode, process messages without spawning workers

    if opts.debug:

        debug_mode()

        return

    # Become a daemon

    daemon_context = daemon.DaemonContext(

        stdout=sys.stdout,

        stderr=sys.stderr,

        umask=022)

    daemon_context.open()

    # Create pidfile. Take care of differences between python-daemon versions.

    try:

        pidf = pidfile.TimeoutPIDLockFile(opts.pid_file, 10)

    except:

        pidf = pidlockfile.TimeoutPIDLockFile(opts.pid_file, 10)

    pidf.acquire()

    logger.info("Became a daemon")

    # Fork workers

    children = []

    i = 0

    while i < opts.workers:

        newpid = os.fork()

        if newpid == 0:

            signal(SIGINT,  _exit_handler)

            signal(SIGTERM, _exit_handler)

            child(sys.argv[1:])

            sys.exit(1)

        else:

            pids = (os.getpid(), newpid)

            logger.debug("%d, forked child: %d" % pids)

            children.append(pids[1])

        i += 1

    # Catch signals to ensure graceful shutdown

    signal(SIGINT,  _parent_handler)

    signal(SIGTERM, _parent_handler)

    # Wait for all children processes to die, one by one

    try :

        for pid in children:

            try:

                os.waitpid(pid, 0)

            except Exception:

                pass

    finally:

        pidf.release()

if __name__ == "__main__":

    sys.exit(main())

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