root / logic / dispatcher.py @ 4ed2e471
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#!/usr/bin/env python
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# Copyright 2011 GRNET S.A. All rights reserved.
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#
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# Redistribution and use in source and binary forms, with or without
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# modification, are permitted provided that the following conditions
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# are met:
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#
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# 1. Redistributions of source code must retain the above copyright
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# notice, this list of conditions and the following disclaimer.
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#
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# 2. Redistributions in binary form must reproduce the above copyright
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# notice, this list of conditions and the following disclaimer in the
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# documentation and/or other materials provided with the distribution.
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#
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# THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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# ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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# OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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# HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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# OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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# SUCH DAMAGE.
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#
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# The views and conclusions contained in the software and documentation are
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# those of the authors and should not be interpreted as representing official
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# policies, either expressed or implied, of GRNET S.A.
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""" Message queue setup and dispatch
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This program sets up connections to the queues configured in settings.py
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and implements the message wait and dispatch loops. Actual messages are
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handled in the dispatched functions.
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"""
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from django.core.management import setup_environ |
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import sys |
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import os |
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path = os.path.normpath(os.path.join(os.getcwd(), '..'))
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sys.path.append(path) |
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import synnefo.settings as settings |
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from synnefo.logic import log |
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setup_environ(settings) |
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from amqplib import client_0_8 as amqp |
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from signal import signal, SIGINT, SIGTERM |
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import time |
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import socket |
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from daemon import daemon |
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# Take care of differences between python-daemon versions.
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try:
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from daemon import pidfile |
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except:
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from daemon import pidlockfile |
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from synnefo.logic import callbacks |
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class Dispatcher: |
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logger = None
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chan = None
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debug = False
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clienttags = [] |
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def __init__(self, debug = False): |
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# Initialize logger
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self.logger = log.get_logger('synnefo.dispatcher') |
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self.debug = debug
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self._init()
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def wait(self): |
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while True: |
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try:
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self.chan.wait()
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except SystemExit: |
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break
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except amqp.exceptions.AMQPConnectionException:
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self.logger.error("Server went away, reconnecting...") |
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self._init()
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except socket.error:
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self.logger.error("Server went away, reconnecting...") |
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self._init()
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[self.chan.basic_cancel(clienttag) for clienttag in self.clienttags] |
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self.chan.connection.close()
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self.chan.close()
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def _init(self): |
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self.logger.info("Initializing") |
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# Connect to RabbitMQ
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conn = None
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while conn == None: |
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self.logger.info("Attempting to connect to %s", |
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settings.RABBIT_HOST) |
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try:
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conn = amqp.Connection(host=settings.RABBIT_HOST, |
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userid=settings.RABBIT_USERNAME, |
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password=settings.RABBIT_PASSWORD, |
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virtual_host=settings.RABBIT_VHOST) |
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except socket.error:
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time.sleep(1)
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self.logger.info("Connection succesful, opening channel") |
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self.chan = conn.channel()
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# Declare queues and exchanges
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for exchange in settings.EXCHANGES: |
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self.chan.exchange_declare(exchange=exchange, type="topic", |
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durable=True, auto_delete=False) |
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for queue in settings.QUEUES: |
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self.chan.queue_declare(queue=queue, durable=True, |
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exclusive=False, auto_delete=False) |
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bindings = settings.BINDINGS |
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# Special queue for debugging, should not appear in production
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if self.debug: |
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self.chan.queue_declare(queue=settings.QUEUE_DEBUG, durable=True, |
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exclusive=False, auto_delete=False) |
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bindings += settings.BINDINGS_DEBUG |
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# Bind queues to handler methods
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for binding in bindings: |
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try:
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callback = getattr(callbacks, binding[3]) |
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except AttributeError: |
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self.logger.error("Cannot find callback %s" % binding[3]) |
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continue
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self.chan.queue_bind(queue=binding[0], exchange=binding[1], |
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routing_key=binding[2])
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tag = self.chan.basic_consume(queue=binding[0], callback=callback) |
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self.logger.debug("Binding %s(%s) to queue %s with handler %s" % |
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(binding[1], binding[2], binding[0], binding[3])) |
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self.clienttags.append(tag)
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def _exit_handler(signum, frame): |
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""""Catch exit signal in children processes."""
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print "%d: Caught signal %d, will raise SystemExit" % (os.getpid(), signum) |
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raise SystemExit |
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def _parent_handler(signum, frame): |
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""""Catch exit signal in parent process and forward it to children."""
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global children
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print "Caught signal %d, sending kill signal to children" % signum |
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[os.kill(pid, SIGTERM) for pid in children] |
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def child(cmdline): |
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"""The context of the child process"""
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# Cmd line argument parsing
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(opts, args) = parse_arguments(cmdline) |
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disp = Dispatcher(debug = opts.debug) |
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# Start the event loop
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disp.wait() |
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def parse_arguments(args): |
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from optparse import OptionParser |
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parser = OptionParser() |
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parser.add_option("-d", "--debug", action="store_true", default=False, |
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dest="debug", help="Enable debug mode") |
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parser.add_option("-c", "--cleanup-queues", action="store_true", |
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default=False, dest="cleanup_queues", |
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help="Remove all declared queues (DANGEROUS!)")
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parser.add_option("-w", "--workers", default=2, dest="workers", |
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help="Number of workers to spawn", type="int") |
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parser.add_option("-p", '--pid-file', dest="pid_file", |
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default=os.path.join(os.getcwd(), "dispatcher.pid"),
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help="Save PID to file (default:%s)" %
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os.path.join(os.getcwd(), "dispatcher.pid"))
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return parser.parse_args(args)
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def cleanup_queues() : |
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"""Delete declared queues from RabbitMQ. Use with care!"""
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conn = amqp.Connection( host=settings.RABBIT_HOST, |
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userid=settings.RABBIT_USERNAME, |
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password=settings.RABBIT_PASSWORD, |
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virtual_host=settings.RABBIT_VHOST) |
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chan = conn.channel() |
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print "Queues to be deleted: ", settings.QUEUES |
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print "Exchnages to be deleted: ", settings.EXCHANGES |
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ans = raw_input("Are you sure (N/y):") |
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if not ans: |
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return
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if ans not in ['Y', 'y']: |
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return
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#for exchange in settings.EXCHANGES:
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# try:
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# chan.exchange_delete(exchange=exchange)
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# except amqp.exceptions.AMQPChannelException as e:
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# print e.amqp_reply_code, " ", e.amqp_reply_text
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for queue in settings.QUEUES: |
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try:
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chan.queue_delete(queue=queue) |
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except amqp.exceptions.AMQPChannelException as e: |
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print e.amqp_reply_code, " ", e.amqp_reply_text |
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chan.close() |
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chan.connection.close() |
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def debug_mode(): |
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disp = Dispatcher(debug = True)
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signal(SIGINT, _exit_handler) |
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signal(SIGTERM, _exit_handler) |
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disp.wait() |
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def main(): |
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global children, logger
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(opts, args) = parse_arguments(sys.argv[1:])
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logger = log.get_logger("synnefo.dispatcher")
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# Special case for the clean up queues action
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if opts.cleanup_queues:
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cleanup_queues() |
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return
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# Debug mode, process messages without spawning workers
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if opts.debug:
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debug_mode() |
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return
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# Become a daemon
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daemon_context = daemon.DaemonContext( |
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stdout=sys.stdout, |
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stderr=sys.stderr, |
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umask=022)
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daemon_context.open() |
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# Create pidfile. Take care of differences between python-daemon versions.
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try:
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pidf = pidfile.TimeoutPIDLockFile(opts.pid_file, 10)
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except:
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pidf = pidlockfile.TimeoutPIDLockFile(opts.pid_file, 10)
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pidf.acquire() |
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logger.info("Became a daemon")
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# Fork workers
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children = [] |
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i = 0
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while i < opts.workers:
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newpid = os.fork() |
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if newpid == 0: |
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signal(SIGINT, _exit_handler) |
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signal(SIGTERM, _exit_handler) |
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child(sys.argv[1:])
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sys.exit(1)
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else:
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pids = (os.getpid(), newpid) |
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logger.debug("%d, forked child: %d" % pids)
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children.append(pids[1])
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i += 1
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# Catch signals to ensure graceful shutdown
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signal(SIGINT, _parent_handler) |
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signal(SIGTERM, _parent_handler) |
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# Wait for all children processes to die, one by one
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try :
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for pid in children: |
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try:
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os.waitpid(pid, 0)
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except Exception: |
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pass
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finally:
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pidf.release() |
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if __name__ == "__main__": |
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sys.exit(main()) |
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# vim: set sta sts=4 shiftwidth=4 sw=4 et ai :
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