This document describes the current stable version of Celery (3.1). For development docs, go here.
Source code for celery.worker.consumer
# -*- coding: utf-8 -*-
"""
celery.worker.consumer
~~~~~~~~~~~~~~~~~~~~~~
This module contains the components responsible for consuming messages
from the broker, processing the messages and keeping the broker connections
up and running.
"""
from __future__ import absolute_import
import errno
import kombu
import logging
import os
import socket
from collections import defaultdict
from functools import partial
from heapq import heappush
from operator import itemgetter
from time import sleep
from billiard.common import restart_state
from billiard.exceptions import RestartFreqExceeded
from kombu.async.semaphore import DummyLock
from kombu.common import QoS, ignore_errors
from kombu.syn import _detect_environment
from kombu.utils.compat import get_errno
from kombu.utils.encoding import safe_repr, bytes_t
from kombu.utils.limits import TokenBucket
from celery import chain
from celery import bootsteps
from celery.app.trace import build_tracer
from celery.canvas import signature
from celery.exceptions import InvalidTaskError
from celery.five import items, values
from celery.utils.functional import noop
from celery.utils.log import get_logger
from celery.utils.objects import Bunch
from celery.utils.text import truncate
from celery.utils.timeutils import humanize_seconds, rate
from . import heartbeat, loops, pidbox
from .state import task_reserved, maybe_shutdown, revoked, reserved_requests
try:
buffer_t = buffer
except NameError: # pragma: no cover
# Py3 does not have buffer, but we only need isinstance.
class buffer_t(object): # noqa
pass
__all__ = [
'Consumer', 'Connection', 'Events', 'Heart', 'Control',
'Tasks', 'Evloop', 'Agent', 'Mingle', 'Gossip', 'dump_body',
]
CLOSE = bootsteps.CLOSE
logger = get_logger(__name__)
debug, info, warn, error, crit = (logger.debug, logger.info, logger.warning,
logger.error, logger.critical)
CONNECTION_RETRY = """\
consumer: Connection to broker lost. \
Trying to re-establish the connection...\
"""
CONNECTION_RETRY_STEP = """\
Trying again {when}...\
"""
CONNECTION_ERROR = """\
consumer: Cannot connect to %s: %s.
%s
"""
CONNECTION_FAILOVER = """\
Will retry using next failover.\
"""
UNKNOWN_FORMAT = """\
Received and deleted unknown message. Wrong destination?!?
The full contents of the message body was: %s
"""
#: Error message for when an unregistered task is received.
UNKNOWN_TASK_ERROR = """\
Received unregistered task of type %s.
The message has been ignored and discarded.
Did you remember to import the module containing this task?
Or maybe you are using relative imports?
Please see http://bit.ly/gLye1c for more information.
The full contents of the message body was:
%s
"""
#: Error message for when an invalid task message is received.
INVALID_TASK_ERROR = """\
Received invalid task message: %s
The message has been ignored and discarded.
Please ensure your message conforms to the task
message protocol as described here: http://bit.ly/hYj41y
The full contents of the message body was:
%s
"""
MESSAGE_DECODE_ERROR = """\
Can't decode message body: %r [type:%r encoding:%r headers:%s]
body: %s
"""
MESSAGE_REPORT = """\
body: {0}
{{content_type:{1} content_encoding:{2}
delivery_info:{3} headers={4}}}
"""
MINGLE_GET_FIELDS = itemgetter('clock', 'revoked')
[docs]def dump_body(m, body):
if isinstance(body, buffer_t):
body = bytes_t(body)
return '{0} ({1}b)'.format(truncate(safe_repr(body), 1024),
len(m.body))
[docs]class Consumer(object):
Strategies = dict
#: set when consumer is shutting down.
in_shutdown = False
#: Optional callback called the first time the worker
#: is ready to receive tasks.
init_callback = None
#: The current worker pool instance.
pool = None
#: A timer used for high-priority internal tasks, such
#: as sending heartbeats.
timer = None
restart_count = -1 # first start is the same as a restart
[docs] class Blueprint(bootsteps.Blueprint):
name = 'Consumer'
default_steps = [
'celery.worker.consumer:Connection',
'celery.worker.consumer:Mingle',
'celery.worker.consumer:Events',
'celery.worker.consumer:Gossip',
'celery.worker.consumer:Heart',
'celery.worker.consumer:Control',
'celery.worker.consumer:Tasks',
'celery.worker.consumer:Evloop',
'celery.worker.consumer:Agent',
]
def __init__(self, on_task_request,
init_callback=noop, hostname=None,
pool=None, app=None,
timer=None, controller=None, hub=None, amqheartbeat=None,
worker_options=None, disable_rate_limits=False,
initial_prefetch_count=2, prefetch_multiplier=1, **kwargs):
self.app = app
self.controller = controller
self.init_callback = init_callback
self.hostname = hostname or socket.gethostname()
self.pid = os.getpid()
self.pool = pool
self.timer = timer
self.strategies = self.Strategies()
conninfo = self.app.connection()
self.connection_errors = conninfo.connection_errors
self.channel_errors = conninfo.channel_errors
self._restart_state = restart_state(maxR=5, maxT=1)
self._does_info = logger.isEnabledFor(logging.INFO)
self.on_task_request = on_task_request
self.on_task_message = set()
self.amqheartbeat_rate = self.app.conf.BROKER_HEARTBEAT_CHECKRATE
self.disable_rate_limits = disable_rate_limits
self.initial_prefetch_count = initial_prefetch_count
self.prefetch_multiplier = prefetch_multiplier
# this contains a tokenbucket for each task type by name, used for
# rate limits, or None if rate limits are disabled for that task.
self.task_buckets = defaultdict(lambda: None)
self.reset_rate_limits()
self.hub = hub
if self.hub:
self.amqheartbeat = amqheartbeat
if self.amqheartbeat is None:
self.amqheartbeat = self.app.conf.BROKER_HEARTBEAT
else:
self.amqheartbeat = 0
if not hasattr(self, 'loop'):
self.loop = loops.asynloop if hub else loops.synloop
if _detect_environment() == 'gevent':
# there's a gevent bug that causes timeouts to not be reset,
# so if the connection timeout is exceeded once, it can NEVER
# connect again.
self.app.conf.BROKER_CONNECTION_TIMEOUT = None
self.steps = []
self.blueprint = self.Blueprint(
app=self.app, on_close=self.on_close,
)
self.blueprint.apply(self, **dict(worker_options or {}, **kwargs))
[docs] def bucket_for_task(self, type):
limit = rate(getattr(type, 'rate_limit', None))
return TokenBucket(limit, capacity=1) if limit else None
[docs] def reset_rate_limits(self):
self.task_buckets.update(
(n, self.bucket_for_task(t)) for n, t in items(self.app.tasks)
)
def _update_prefetch_count(self, index=0):
"""Update prefetch count after pool/shrink grow operations.
Index must be the change in number of processes as a positive
(increasing) or negative (decreasing) number.
.. note::
Currently pool grow operations will end up with an offset
of +1 if the initial size of the pool was 0 (e.g.
``--autoscale=1,0``).
"""
num_processes = self.pool.num_processes
if not self.initial_prefetch_count or not num_processes:
return # prefetch disabled
self.initial_prefetch_count = (
self.pool.num_processes * self.prefetch_multiplier
)
return self._update_qos_eventually(index)
def _update_qos_eventually(self, index):
return (self.qos.decrement_eventually if index < 0
else self.qos.increment_eventually)(
abs(index) * self.prefetch_multiplier)
def _limit_task(self, request, bucket, tokens):
if not bucket.can_consume(tokens):
hold = bucket.expected_time(tokens)
self.timer.call_after(
hold, self._limit_task, (request, bucket, tokens),
)
else:
task_reserved(request)
self.on_task_request(request)
[docs] def start(self):
blueprint = self.blueprint
while blueprint.state != CLOSE:
self.restart_count += 1
maybe_shutdown()
try:
blueprint.start(self)
except self.connection_errors as exc:
if isinstance(exc, OSError) and get_errno(exc) == errno.EMFILE:
raise # Too many open files
maybe_shutdown()
try:
self._restart_state.step()
except RestartFreqExceeded as exc:
crit('Frequent restarts detected: %r', exc, exc_info=1)
sleep(1)
if blueprint.state != CLOSE and self.connection:
warn(CONNECTION_RETRY, exc_info=True)
try:
self.connection.collect()
except Exception:
pass
self.on_close()
blueprint.restart(self)
[docs] def register_with_event_loop(self, hub):
self.blueprint.send_all(
self, 'register_with_event_loop', args=(hub, ),
description='Hub.register',
)
[docs] def on_ready(self):
callback, self.init_callback = self.init_callback, None
if callback:
callback(self)
[docs] def loop_args(self):
return (self, self.connection, self.task_consumer,
self.blueprint, self.hub, self.qos, self.amqheartbeat,
self.app.clock, self.amqheartbeat_rate)
[docs] def on_decode_error(self, message, exc):
"""Callback called if an error occurs while decoding
a message received.
Simply logs the error and acknowledges the message so it
doesn't enter a loop.
:param message: The message with errors.
:param exc: The original exception instance.
"""
crit(MESSAGE_DECODE_ERROR,
exc, message.content_type, message.content_encoding,
safe_repr(message.headers), dump_body(message, message.body),
exc_info=1)
message.ack()
[docs] def on_close(self):
# Clear internal queues to get rid of old messages.
# They can't be acked anyway, as a delivery tag is specific
# to the current channel.
if self.controller and self.controller.semaphore:
self.controller.semaphore.clear()
if self.timer:
self.timer.clear()
reserved_requests.clear()
if self.pool and self.pool.flush:
self.pool.flush()
[docs] def connect(self):
"""Establish the broker connection.
Will retry establishing the connection if the
:setting:`BROKER_CONNECTION_RETRY` setting is enabled
"""
conn = self.app.connection(heartbeat=self.amqheartbeat)
# Callback called for each retry while the connection
# can't be established.
def _error_handler(exc, interval, next_step=CONNECTION_RETRY_STEP):
if getattr(conn, 'alt', None) and interval == 0:
next_step = CONNECTION_FAILOVER
error(CONNECTION_ERROR, conn.as_uri(), exc,
next_step.format(when=humanize_seconds(interval, 'in', ' ')))
# remember that the connection is lazy, it won't establish
# until needed.
if not self.app.conf.BROKER_CONNECTION_RETRY:
# retry disabled, just call connect directly.
conn.connect()
return conn
conn = conn.ensure_connection(
_error_handler, self.app.conf.BROKER_CONNECTION_MAX_RETRIES,
callback=maybe_shutdown,
)
if self.hub:
conn.transport.register_with_event_loop(conn.connection, self.hub)
return conn
[docs] def add_task_queue(self, queue, exchange=None, exchange_type=None,
routing_key=None, **options):
cset = self.task_consumer
queues = self.app.amqp.queues
# Must use in' here, as __missing__ will automatically
# create queues when CELERY_CREATE_MISSING_QUEUES is enabled.
# (Issue #1079)
if queue in queues:
q = queues[queue]
else:
exchange = queue if exchange is None else exchange
exchange_type = ('direct' if exchange_type is None
else exchange_type)
q = queues.select_add(queue,
exchange=exchange,
exchange_type=exchange_type,
routing_key=routing_key, **options)
if not cset.consuming_from(queue):
cset.add_queue(q)
cset.consume()
info('Started consuming from %s', queue)
[docs] def cancel_task_queue(self, queue):
info('Canceling queue %s', queue)
self.app.amqp.queues.deselect(queue)
self.task_consumer.cancel_by_queue(queue)
[docs] def apply_eta_task(self, task):
"""Method called by the timer to apply a task with an
ETA/countdown."""
task_reserved(task)
self.on_task_request(task)
self.qos.decrement_eventually()
def _message_report(self, body, message):
return MESSAGE_REPORT.format(dump_body(message, body),
safe_repr(message.content_type),
safe_repr(message.content_encoding),
safe_repr(message.delivery_info),
safe_repr(message.headers))
[docs] def on_unknown_message(self, body, message):
warn(UNKNOWN_FORMAT, self._message_report(body, message))
message.reject_log_error(logger, self.connection_errors)
[docs] def on_unknown_task(self, body, message, exc):
error(UNKNOWN_TASK_ERROR, exc, dump_body(message, body), exc_info=True)
message.reject_log_error(logger, self.connection_errors)
[docs] def on_invalid_task(self, body, message, exc):
error(INVALID_TASK_ERROR, exc, dump_body(message, body), exc_info=True)
message.reject_log_error(logger, self.connection_errors)
[docs] def update_strategies(self):
loader = self.app.loader
for name, task in items(self.app.tasks):
self.strategies[name] = task.start_strategy(self.app, self)
task.__trace__ = build_tracer(name, task, loader, self.hostname,
app=self.app)
[docs] def create_task_handler(self):
strategies = self.strategies
on_unknown_message = self.on_unknown_message
on_unknown_task = self.on_unknown_task
on_invalid_task = self.on_invalid_task
callbacks = self.on_task_message
def on_task_received(body, message):
headers = message.headers
try:
type_, is_proto2 = body['task'], 0
except (KeyError, TypeError):
try:
type_, is_proto2 = headers['task'], 1
except (KeyError, TypeError):
return on_unknown_message(body, message)
if is_proto2:
body = proto2_to_proto1(
self.app, type_, body, message, headers)
try:
strategies[type_](message, body,
message.ack_log_error,
message.reject_log_error,
callbacks)
except KeyError as exc:
on_unknown_task(body, message, exc)
except InvalidTaskError as exc:
on_invalid_task(body, message, exc)
return on_task_received
def __repr__(self):
return '<Consumer: {self.hostname} ({state})>'.format(
self=self, state=self.blueprint.human_state(),
)
def proto2_to_proto1(app, type_, body, message, headers):
args, kwargs, embed = body
embedded = _extract_proto2_embed(**embed)
chained = embedded.pop('chain')
new_body = dict(
_extract_proto2_headers(type_, **headers),
args=args,
kwargs=kwargs,
**embedded)
if chained:
new_body['callbacks'].append(chain(chained, app=app))
return new_body
def _extract_proto2_headers(type_, id, retries, eta, expires,
group, timelimit, **_):
return {
'id': id,
'task': type_,
'retries': retries,
'eta': eta,
'expires': expires,
'utc': True,
'taskset': group,
'timelimit': timelimit,
}
def _extract_proto2_embed(callbacks, errbacks, chain, chord, **_):
return {
'callbacks': callbacks or [],
'errbacks': errbacks,
'chain': chain,
'chord': chord,
}
[docs]class Connection(bootsteps.StartStopStep):
def __init__(self, c, **kwargs):
c.connection = None
[docs] def start(self, c):
c.connection = c.connect()
info('Connected to %s', c.connection.as_uri())
[docs] def shutdown(self, c):
# We must set self.connection to None here, so
# that the green pidbox thread exits.
connection, c.connection = c.connection, None
if connection:
ignore_errors(connection, connection.close)
[docs] def info(self, c, params='N/A'):
if c.connection:
params = c.connection.info()
params.pop('password', None) # don't send password.
return {'broker': params}
[docs]class Events(bootsteps.StartStopStep):
requires = (Connection, )
def __init__(self, c, send_events=None, **kwargs):
self.send_events = True
self.groups = None if send_events else ['worker']
c.event_dispatcher = None
[docs] def start(self, c):
# flush events sent while connection was down.
prev = self._close(c)
dis = c.event_dispatcher = c.app.events.Dispatcher(
c.connect(), hostname=c.hostname,
enabled=self.send_events, groups=self.groups,
)
if prev:
dis.extend_buffer(prev)
dis.flush()
def _close(self, c):
if c.event_dispatcher:
dispatcher = c.event_dispatcher
# remember changes from remote control commands:
self.groups = dispatcher.groups
# close custom connection
if dispatcher.connection:
ignore_errors(c, dispatcher.connection.close)
ignore_errors(c, dispatcher.close)
c.event_dispatcher = None
return dispatcher
[docs]class Heart(bootsteps.StartStopStep):
requires = (Events, )
def __init__(self, c, without_heartbeat=False, heartbeat_interval=None,
**kwargs):
self.enabled = not without_heartbeat
self.heartbeat_interval = heartbeat_interval
c.heart = None
[docs] def start(self, c):
c.heart = heartbeat.Heart(
c.timer, c.event_dispatcher, self.heartbeat_interval,
)
c.heart.start()
shutdown = stop
[docs]class Mingle(bootsteps.StartStopStep):
label = 'Mingle'
requires = (Events, )
compatible_transports = set(['amqp', 'redis'])
def __init__(self, c, without_mingle=False, **kwargs):
self.enabled = not without_mingle and self.compatible_transport(c.app)
[docs] def compatible_transport(self, app):
with app.connection() as conn:
return conn.transport.driver_type in self.compatible_transports
[docs] def start(self, c):
info('mingle: searching for neighbors')
I = c.app.control.inspect(timeout=1.0, connection=c.connection)
replies = I.hello(c.hostname, revoked._data) or {}
replies.pop(c.hostname, None)
if replies:
info('mingle: sync with %s nodes',
len([reply for reply, value in items(replies) if value]))
for reply in values(replies):
if reply:
try:
other_clock, other_revoked = MINGLE_GET_FIELDS(reply)
except KeyError: # reply from pre-3.1 worker
pass
else:
c.app.clock.adjust(other_clock)
revoked.update(other_revoked)
info('mingle: sync complete')
else:
info('mingle: all alone')
[docs]class Tasks(bootsteps.StartStopStep):
requires = (Mingle, )
def __init__(self, c, **kwargs):
c.task_consumer = c.qos = None
[docs] def start(self, c):
c.update_strategies()
# - RabbitMQ 3.3 completely redefines how basic_qos works..
# This will detect if the new qos smenatics is in effect,
# and if so make sure the 'apply_global' flag is set on qos updates.
qos_global = not c.connection.qos_semantics_matches_spec
# set initial prefetch count
c.connection.default_channel.basic_qos(
0, c.initial_prefetch_count, qos_global,
)
c.task_consumer = c.app.amqp.TaskConsumer(
c.connection, on_decode_error=c.on_decode_error,
)
def set_prefetch_count(prefetch_count):
return c.task_consumer.qos(
prefetch_count=prefetch_count,
apply_global=qos_global,
)
c.qos = QoS(set_prefetch_count, c.initial_prefetch_count)
[docs] def stop(self, c):
if c.task_consumer:
debug('Canceling task consumer...')
ignore_errors(c, c.task_consumer.cancel)
[docs] def shutdown(self, c):
if c.task_consumer:
self.stop(c)
debug('Closing consumer channel...')
ignore_errors(c, c.task_consumer.close)
c.task_consumer = None
[docs]class Agent(bootsteps.StartStopStep):
conditional = True
requires = (Connection, )
def __init__(self, c, **kwargs):
self.agent_cls = self.enabled = c.app.conf.CELERYD_AGENT
[docs] def create(self, c):
agent = c.agent = self.instantiate(self.agent_cls, c.connection)
return agent
[docs]class Control(bootsteps.StartStopStep):
requires = (Tasks, )
def __init__(self, c, **kwargs):
self.is_green = c.pool is not None and c.pool.is_green
self.box = (pidbox.gPidbox if self.is_green else pidbox.Pidbox)(c)
self.start = self.box.start
self.stop = self.box.stop
self.shutdown = self.box.shutdown
[docs]class Gossip(bootsteps.ConsumerStep):
label = 'Gossip'
requires = (Mingle, )
_cons_stamp_fields = itemgetter(
'id', 'clock', 'hostname', 'pid', 'topic', 'action', 'cver',
)
compatible_transports = set(['amqp', 'redis'])
def __init__(self, c, without_gossip=False, interval=5.0, **kwargs):
self.enabled = not without_gossip and self.compatible_transport(c.app)
self.app = c.app
c.gossip = self
self.Receiver = c.app.events.Receiver
self.hostname = c.hostname
self.full_hostname = '.'.join([self.hostname, str(c.pid)])
self.on = Bunch(
node_join=set(),
node_leave=set(),
node_lost=set(),
)
self.timer = c.timer
if self.enabled:
self.state = c.app.events.State(
on_node_join=self.on_node_join,
on_node_leave=self.on_node_leave,
max_tasks_in_memory=1,
)
if c.hub:
c._mutex = DummyLock()
self.update_state = self.state.event
self.interval = interval
self._tref = None
self.consensus_requests = defaultdict(list)
self.consensus_replies = {}
self.event_handlers = {
'worker.elect': self.on_elect,
'worker.elect.ack': self.on_elect_ack,
}
self.clock = c.app.clock
self.election_handlers = {
'task': self.call_task
}
[docs] def compatible_transport(self, app):
with app.connection() as conn:
return conn.transport.driver_type in self.compatible_transports
[docs] def election(self, id, topic, action=None):
self.consensus_replies[id] = []
self.dispatcher.send(
'worker-elect',
id=id, topic=topic, action=action, cver=1,
)
[docs] def call_task(self, task):
try:
signature(task, app=self.app).apply_async()
except Exception as exc:
error('Could not call task: %r', exc, exc_info=1)
[docs] def on_elect(self, event):
try:
(id_, clock, hostname, pid,
topic, action, _) = self._cons_stamp_fields(event)
except KeyError as exc:
return error('election request missing field %s', exc, exc_info=1)
heappush(
self.consensus_requests[id_],
(clock, '%s.%s' % (hostname, pid), topic, action),
)
self.dispatcher.send('worker-elect-ack', id=id_)
[docs] def on_elect_ack(self, event):
id = event['id']
try:
replies = self.consensus_replies[id]
except KeyError:
return # not for us
alive_workers = self.state.alive_workers()
replies.append(event['hostname'])
if len(replies) >= len(alive_workers):
_, leader, topic, action = self.clock.sort_heap(
self.consensus_requests[id],
)
if leader == self.full_hostname:
info('I won the election %r', id)
try:
handler = self.election_handlers[topic]
except KeyError:
error('Unknown election topic %r', topic, exc_info=1)
else:
handler(action)
else:
info('node %s elected for %r', leader, id)
self.consensus_requests.pop(id, None)
self.consensus_replies.pop(id, None)
[docs] def on_node_join(self, worker):
debug('%s joined the party', worker.hostname)
self._call_handlers(self.on.node_join, worker)
[docs] def on_node_leave(self, worker):
debug('%s left', worker.hostname)
self._call_handlers(self.on.node_leave, worker)
[docs] def on_node_lost(self, worker):
info('missed heartbeat from %s', worker.hostname)
self._call_handlers(self.on.node_lost, worker)
def _call_handlers(self, handlers, *args, **kwargs):
for handler in handlers:
try:
handler(*args, **kwargs)
except Exception as exc:
error('Ignored error from handler %r: %r',
handler, exc, exc_info=1)
[docs] def register_timer(self):
if self._tref is not None:
self._tref.cancel()
self._tref = self.timer.call_repeatedly(self.interval, self.periodic)
[docs] def periodic(self):
workers = self.state.workers
dirty = set()
for worker in values(workers):
if not worker.alive:
dirty.add(worker)
self.on_node_lost(worker)
for worker in dirty:
workers.pop(worker.hostname, None)
[docs] def get_consumers(self, channel):
self.register_timer()
ev = self.Receiver(channel, routing_key='worker.#')
return [kombu.Consumer(
channel,
queues=[ev.queue],
on_message=partial(self.on_message, ev.event_from_message),
no_ack=True
)]
[docs] def on_message(self, prepare, message):
_type = message.delivery_info['routing_key']
# For redis when `fanout_patterns=False` (See Issue #1882)
if _type.split('.', 1)[0] == 'task':
return
try:
handler = self.event_handlers[_type]
except KeyError:
pass
else:
return handler(message.payload)
hostname = (message.headers.get('hostname') or
message.payload['hostname'])
if hostname != self.hostname:
type, event = prepare(message.payload)
self.update_state(event)
else:
self.clock.forward()
