This document describes the current stable version of Kombu (5.3). For development docs, go here.

Source code for kombu.pidbox

"""Generic process mailbox."""

from __future__ import annotations

import socket
import warnings
from collections import defaultdict, deque
from contextlib import contextmanager
from copy import copy
from itertools import count
from time import time

from . import Consumer, Exchange, Producer, Queue
from .clocks import LamportClock
from .common import maybe_declare, oid_from
from .exceptions import InconsistencyError
from .log import get_logger
from .matcher import match
from .utils.functional import maybe_evaluate, reprcall
from .utils.objects import cached_property
from .utils.uuid import uuid


A node named {node.hostname} is already using this process mailbox!

Maybe you forgot to shutdown the other node or did not do so properly?
Or if you meant to start multiple nodes on the same host please make sure
you give each node a unique node name!

__all__ = ('Node', 'Mailbox')
logger = get_logger(__name__)
debug, error = logger.debug, logger.error

[docs] class Node: """Mailbox node.""" #: hostname of the node. hostname = None #: the :class:`Mailbox` this is a node for. mailbox = None #: map of method name/handlers. handlers = None #: current context (passed on to handlers) state = None #: current channel. channel = None def __init__(self, hostname, state=None, channel=None, handlers=None, mailbox=None): = channel self.mailbox = mailbox self.hostname = hostname self.state = state self.adjust_clock = self.mailbox.clock.adjust if handlers is None: handlers = {} self.handlers = handlers
[docs] def Consumer(self, channel=None, no_ack=True, accept=None, **options): queue = self.mailbox.get_queue(self.hostname) def verify_exclusive(name, messages, consumers): if consumers: warnings.warn(W_PIDBOX_IN_USE.format(node=self)) queue.on_declared = verify_exclusive return Consumer( channel or, [queue], no_ack=no_ack, accept=self.mailbox.accept if accept is None else accept, **options )
[docs] def handler(self, fun): self.handlers[fun.__name__] = fun return fun
def on_decode_error(self, message, exc): error('Cannot decode message: %r', exc, exc_info=1)
[docs] def listen(self, channel=None, callback=None): consumer = self.Consumer(channel=channel, callbacks=[callback or self.handle_message], on_decode_error=self.on_decode_error) consumer.consume() return consumer
[docs] def dispatch(self, method, arguments=None, reply_to=None, ticket=None, **kwargs): arguments = arguments or {} debug('pidbox received method %s [reply_to:%s ticket:%s]', reprcall(method, (), kwargs=arguments), reply_to, ticket) handle = reply_to and self.handle_call or self.handle_cast try: reply = handle(method, arguments) except SystemExit: raise except Exception as exc: error('pidbox command error: %r', exc, exc_info=1) reply = {'error': repr(exc)} if reply_to: self.reply({self.hostname: reply}, exchange=reply_to['exchange'], routing_key=reply_to['routing_key'], ticket=ticket) return reply
[docs] def handle(self, method, arguments=None): arguments = {} if not arguments else arguments return self.handlers[method](self.state, **arguments)
[docs] def handle_call(self, method, arguments): return self.handle(method, arguments)
[docs] def handle_cast(self, method, arguments): return self.handle(method, arguments)
[docs] def handle_message(self, body, message=None): destination = body.get('destination') pattern = body.get('pattern') matcher = body.get('matcher') if message: self.adjust_clock(message.headers.get('clock') or 0) hostname = self.hostname run_dispatch = False if destination: if hostname in destination: run_dispatch = True elif pattern and matcher: if match(hostname, pattern, matcher): run_dispatch = True else: run_dispatch = True if run_dispatch: return self.dispatch(**body)
dispatch_from_message = handle_message
[docs] def reply(self, data, exchange, routing_key, ticket, **kwargs): self.mailbox._publish_reply(data, exchange, routing_key, ticket,, serializer=self.mailbox.serializer)
[docs] class Mailbox: """Process Mailbox.""" node_cls = Node exchange_fmt = '%s.pidbox' reply_exchange_fmt = 'reply.%s.pidbox' #: Name of application. namespace = None #: Connection (if bound). connection = None #: Exchange type (usually direct, or fanout for broadcast). type = 'direct' #: mailbox exchange (init by constructor). exchange = None #: exchange to send replies to. reply_exchange = None #: Only accepts json messages by default. accept = ['json'] #: Message serializer serializer = None def __init__(self, namespace, type='direct', connection=None, clock=None, accept=None, serializer=None, producer_pool=None, queue_ttl=None, queue_expires=None, reply_queue_ttl=None, reply_queue_expires=10.0): self.namespace = namespace self.connection = connection self.type = type self.clock = LamportClock() if clock is None else clock = self._get_exchange(self.namespace, self.type) self.reply_exchange = self._get_reply_exchange(self.namespace) self.unclaimed = defaultdict(deque) self.accept = self.accept if accept is None else accept self.serializer = self.serializer if serializer is None else serializer self.queue_ttl = queue_ttl self.queue_expires = queue_expires self.reply_queue_ttl = reply_queue_ttl self.reply_queue_expires = reply_queue_expires self._producer_pool = producer_pool def __call__(self, connection): bound = copy(self) bound.connection = connection return bound
[docs] def Node(self, hostname=None, state=None, channel=None, handlers=None): hostname = hostname or socket.gethostname() return self.node_cls(hostname, state, channel, handlers, mailbox=self)
[docs] def call(self, destination, command, kwargs=None, timeout=None, callback=None, channel=None): kwargs = {} if not kwargs else kwargs return self._broadcast(command, kwargs, destination, reply=True, timeout=timeout, callback=callback, channel=channel)
[docs] def cast(self, destination, command, kwargs=None): kwargs = {} if not kwargs else kwargs return self._broadcast(command, kwargs, destination, reply=False)
[docs] def abcast(self, command, kwargs=None): kwargs = {} if not kwargs else kwargs return self._broadcast(command, kwargs, reply=False)
[docs] def multi_call(self, command, kwargs=None, timeout=1, limit=None, callback=None, channel=None): kwargs = {} if not kwargs else kwargs return self._broadcast(command, kwargs, reply=True, timeout=timeout, limit=limit, callback=callback, channel=channel)
[docs] def get_reply_queue(self): oid = self.oid return Queue( f'{oid}.{}', exchange=self.reply_exchange, routing_key=oid, durable=False, auto_delete=True, expires=self.reply_queue_expires, message_ttl=self.reply_queue_ttl, )
@cached_property def reply_queue(self): return self.get_reply_queue()
[docs] def get_queue(self, hostname): return Queue( f'{hostname}.{self.namespace}.pidbox',, durable=False, auto_delete=True, expires=self.queue_expires, message_ttl=self.queue_ttl, )
@contextmanager def producer_or_acquire(self, producer=None, channel=None): if producer: yield producer elif self.producer_pool: with self.producer_pool.acquire() as producer: yield producer else: yield Producer(channel, auto_declare=False) def _publish_reply(self, reply, exchange, routing_key, ticket, channel=None, producer=None, **opts): chan = channel or self.connection.default_channel exchange = Exchange(exchange, exchange_type='direct', delivery_mode='transient', durable=False) with self.producer_or_acquire(producer, chan) as producer: try: producer.publish( reply, exchange=exchange, routing_key=routing_key, declare=[exchange], headers={ 'ticket': ticket, 'clock': self.clock.forward(), }, retry=True, **opts ) except InconsistencyError: # queue probably deleted and no one is expecting a reply. pass def _publish(self, type, arguments, destination=None, reply_ticket=None, channel=None, timeout=None, serializer=None, producer=None, pattern=None, matcher=None): message = {'method': type, 'arguments': arguments, 'destination': destination, 'pattern': pattern, 'matcher': matcher} chan = channel or self.connection.default_channel exchange = if reply_ticket: maybe_declare(self.reply_queue(chan)) message.update(ticket=reply_ticket, reply_to={'exchange':, 'routing_key': self.oid}) serializer = serializer or self.serializer with self.producer_or_acquire(producer, chan) as producer: producer.publish( message,, declare=[exchange], headers={'clock': self.clock.forward(), 'expires': time() + timeout if timeout else 0}, serializer=serializer, retry=True, ) def _broadcast(self, command, arguments=None, destination=None, reply=False, timeout=1, limit=None, callback=None, channel=None, serializer=None, pattern=None, matcher=None): if destination is not None and \ not isinstance(destination, (list, tuple)): raise ValueError( 'destination must be a list/tuple not {}'.format( type(destination))) if (pattern is not None and not isinstance(pattern, str) and matcher is not None and not isinstance(matcher, str)): raise ValueError( 'pattern and matcher must be ' 'strings not {}, {}'.format(type(pattern), type(matcher)) ) arguments = arguments or {} reply_ticket = reply and uuid() or None chan = channel or self.connection.default_channel # Set reply limit to number of destinations (if specified) if limit is None and destination: limit = destination and len(destination) or None serializer = serializer or self.serializer self._publish(command, arguments, destination=destination, reply_ticket=reply_ticket, channel=chan, timeout=timeout, serializer=serializer, pattern=pattern, matcher=matcher) if reply_ticket: return self._collect(reply_ticket, limit=limit, timeout=timeout, callback=callback, channel=chan) def _collect(self, ticket, limit=None, timeout=1, callback=None, channel=None, accept=None): if accept is None: accept = self.accept chan = channel or self.connection.default_channel queue = self.reply_queue consumer = Consumer(chan, [queue], accept=accept, no_ack=True) responses = [] unclaimed = self.unclaimed adjust_clock = self.clock.adjust try: return unclaimed.pop(ticket) except KeyError: pass def on_message(body, message): # ticket header added in kombu 2.5 header = message.headers.get adjust_clock(header('clock') or 0) expires = header('expires') if expires and time() > expires: return this_id = header('ticket', ticket) if this_id == ticket: if callback: callback(body) responses.append(body) else: unclaimed[this_id].append(body) consumer.register_callback(on_message) try: with consumer: for i in limit and range(limit) or count(): try: self.connection.drain_events(timeout=timeout) except socket.timeout: break return responses finally: chan.after_reply_message_received( def _get_exchange(self, namespace, type): return Exchange(self.exchange_fmt % namespace, type=type, durable=False, delivery_mode='transient') def _get_reply_exchange(self, namespace): return Exchange(self.reply_exchange_fmt % namespace, type='direct', durable=False, delivery_mode='transient') @property def oid(self): return oid_from(self) @cached_property def producer_pool(self): return maybe_evaluate(self._producer_pool)