This document describes the current stable version of Celery (4.0). For development docs, go here.

Source code for celery.backends.amqp

# -*- coding: utf-8 -*-
"""The old AMQP result backend, deprecated and replaced by the RPC backend."""
from __future__ import absolute_import, unicode_literals

import socket

from collections import deque
from operator import itemgetter

from kombu import Exchange, Queue, Producer, Consumer

from celery import states
from celery.exceptions import TimeoutError
from celery.five import range, monotonic
from celery.utils import deprecated
from celery.utils.log import get_logger

from .base import BaseBackend

__all__ = ['BacklogLimitExceeded', 'AMQPBackend']

logger = get_logger(__name__)

[docs]class BacklogLimitExceeded(Exception): """Too much state history to fast-forward."""
def repair_uuid(s): # Historically the dashes in UUIDS are removed from AMQ entity names, # but there's no known reason to. Hopefully we'll be able to fix # this in v4.0. return '%s-%s-%s-%s-%s' % (s[:8], s[8:12], s[12:16], s[16:20], s[20:]) class NoCacheQueue(Queue): can_cache_declaration = False
[docs]class AMQPBackend(BaseBackend): """The AMQP result backend. Deprecated: Please use the RPC backend or a persistent backend. """ Exchange = Exchange Queue = NoCacheQueue Consumer = Consumer Producer = Producer BacklogLimitExceeded = BacklogLimitExceeded persistent = True supports_autoexpire = True supports_native_join = True retry_policy = { 'max_retries': 20, 'interval_start': 0, 'interval_step': 1, 'interval_max': 1, } def __init__(self, app, connection=None, exchange=None, exchange_type=None, persistent=None, serializer=None, auto_delete=True, **kwargs): deprecated.warn( 'The AMQP result backend', deprecation='4.0', removal='5.0', alternative='Please use RPC backend or a persistent backend.') super(AMQPBackend, self).__init__(app, **kwargs) conf = self._connection = connection self.persistent = self.prepare_persistent(persistent) self.delivery_mode = 2 if self.persistent else 1 exchange = exchange or conf.result_exchange exchange_type = exchange_type or conf.result_exchange_type = self._create_exchange( exchange, exchange_type, self.delivery_mode, ) self.serializer = serializer or conf.result_serializer self.auto_delete = auto_delete def _create_exchange(self, name, type='direct', delivery_mode=2): return self.Exchange(name=name, type=type, delivery_mode=delivery_mode, durable=self.persistent, auto_delete=False) def _create_binding(self, task_id): name = self.rkey(task_id) return self.Queue( name=name,, routing_key=name, durable=self.persistent, auto_delete=self.auto_delete, expires=self.expires, )
[docs] def revive(self, channel): pass
[docs] def rkey(self, task_id): return task_id.replace('-', '')
[docs] def destination_for(self, task_id, request): if request: return self.rkey(task_id), request.correlation_id or task_id return self.rkey(task_id), task_id
[docs] def store_result(self, task_id, result, state, traceback=None, request=None, **kwargs): """Send task return value and state.""" routing_key, correlation_id = self.destination_for(task_id, request) if not routing_key: return with as producer: producer.publish( {'task_id': task_id, 'status': state, 'result': self.encode_result(result, state), 'traceback': traceback, 'children': self.current_task_children(request)},, routing_key=routing_key, correlation_id=correlation_id, serializer=self.serializer, retry=True, retry_policy=self.retry_policy, declare=self.on_reply_declare(task_id), delivery_mode=self.delivery_mode, ) return result
[docs] def on_reply_declare(self, task_id): return [self._create_binding(task_id)]
[docs] def wait_for(self, task_id, timeout=None, cache=True, no_ack=True, on_interval=None, READY_STATES=states.READY_STATES, PROPAGATE_STATES=states.PROPAGATE_STATES, **kwargs): cached_meta = self._cache.get(task_id) if cache and cached_meta and \ cached_meta['status'] in READY_STATES: return cached_meta else: try: return self.consume(task_id, timeout=timeout, no_ack=no_ack, on_interval=on_interval) except socket.timeout: raise TimeoutError('The operation timed out.')
[docs] def get_task_meta(self, task_id, backlog_limit=1000): # Polling and using basic_get with as (_, channel): binding = self._create_binding(task_id)(channel) binding.declare() prev = latest = acc = None for i in range(backlog_limit): # spool ffwd acc = binding.get( accept=self.accept, no_ack=False, ) if not acc: # no more messages break if acc.payload['task_id'] == task_id: prev, latest = latest, acc if prev: # backends are not expected to keep history, # so we delete everything except the most recent state. prev.ack() prev = None else: raise self.BacklogLimitExceeded(task_id) if latest: payload = self._cache[task_id] = self.meta_from_decoded( latest.payload) latest.requeue() return payload else: # no new state, use previous try: return self._cache[task_id] except KeyError: # result probably pending. return {'status': states.PENDING, 'result': None}
poll = get_task_meta # XXX compat
[docs] def drain_events(self, connection, consumer, timeout=None, on_interval=None, now=monotonic, wait=None): wait = wait or connection.drain_events results = {} def callback(meta, message): if meta['status'] in states.READY_STATES: results[meta['task_id']] = self.meta_from_decoded(meta) consumer.callbacks[:] = [callback] time_start = now() while 1: # Total time spent may exceed a single call to wait() if timeout and now() - time_start >= timeout: raise socket.timeout() try: wait(timeout=1) except socket.timeout: pass if on_interval: on_interval() if results: # got event on the wanted channel. break self._cache.update(results) return results
[docs] def consume(self, task_id, timeout=None, no_ack=True, on_interval=None): wait = self.drain_events with as (conn, channel): binding = self._create_binding(task_id) with self.Consumer(channel, binding, no_ack=no_ack, accept=self.accept) as consumer: while 1: try: return wait( conn, consumer, timeout, on_interval)[task_id] except KeyError: continue
def _many_bindings(self, ids): return [self._create_binding(task_id) for task_id in ids]
[docs] def get_many(self, task_ids, timeout=None, no_ack=True, on_message=None, on_interval=None, now=monotonic, getfields=itemgetter('status', 'task_id'), READY_STATES=states.READY_STATES, PROPAGATE_STATES=states.PROPAGATE_STATES, **kwargs): with as (conn, channel): ids = set(task_ids) cached_ids = set() mark_cached = cached_ids.add for task_id in ids: try: cached = self._cache[task_id] except KeyError: pass else: if cached['status'] in READY_STATES: yield task_id, cached mark_cached(task_id) ids.difference_update(cached_ids) results = deque() push_result = results.append push_cache = self._cache.__setitem__ decode_result = self.meta_from_decoded def _on_message(message): body = decode_result(message.decode()) if on_message is not None: on_message(body) state, uid = getfields(body) if state in READY_STATES: push_result(body) \ if uid in task_ids else push_cache(uid, body) bindings = self._many_bindings(task_ids) with self.Consumer(channel, bindings, on_message=_on_message, accept=self.accept, no_ack=no_ack): wait = conn.drain_events popleft = results.popleft while ids: wait(timeout=timeout) while results: state = popleft() task_id = state['task_id'] ids.discard(task_id) push_cache(task_id, state) yield task_id, state if on_interval: on_interval()
[docs] def reload_task_result(self, task_id): raise NotImplementedError( 'reload_task_result is not supported by this backend.')
[docs] def reload_group_result(self, task_id): """Reload group result, even if it has been previously fetched.""" raise NotImplementedError( 'reload_group_result is not supported by this backend.')
[docs] def save_group(self, group_id, result): raise NotImplementedError( 'save_group is not supported by this backend.')
[docs] def restore_group(self, group_id, cache=True): raise NotImplementedError( 'restore_group is not supported by this backend.')
[docs] def delete_group(self, group_id): raise NotImplementedError( 'delete_group is not supported by this backend.')
def __reduce__(self, args=(), kwargs={}): kwargs.update( connection=self._connection,,, persistent=self.persistent, serializer=self.serializer, auto_delete=self.auto_delete, expires=self.expires, ) return super(AMQPBackend, self).__reduce__(args, kwargs)
[docs] def as_uri(self, include_password=True): return 'amqp://'