This document describes the current stable version of Celery (5.2). For development docs, go here.
Source code for celery.worker.consumer.consumer
"""Worker Consumer Blueprint.
This module contains the components responsible for consuming messages
from the broker, processing the messages and keeping the broker connections
up and running.
"""
import errno
import logging
import os
import warnings
from collections import defaultdict
from time import sleep
from billiard.common import restart_state
from billiard.exceptions import RestartFreqExceeded
from kombu.asynchronous.semaphore import DummyLock
from kombu.exceptions import ContentDisallowed, DecodeError
from kombu.utils.compat import _detect_environment
from kombu.utils.encoding import safe_repr
from kombu.utils.limits import TokenBucket
from vine import ppartial, promise
from celery import bootsteps, signals
from celery.app.trace import build_tracer
from celery.exceptions import (CPendingDeprecationWarning, InvalidTaskError,
NotRegistered)
from celery.utils.functional import noop
from celery.utils.log import get_logger
from celery.utils.nodenames import gethostname
from celery.utils.objects import Bunch
from celery.utils.text import truncate
from celery.utils.time import humanize_seconds, rate
from celery.worker import loops
from celery.worker.state import (active_requests, maybe_shutdown,
reserved_requests, task_reserved)
__all__ = ('Consumer', 'Evloop', 'dump_body')
CLOSE = bootsteps.CLOSE
TERMINATE = bootsteps.TERMINATE
STOP_CONDITIONS = {CLOSE, TERMINATE}
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}... ({retries}/{max_retries})\
"""
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're using relative imports?
Please see
http://docs.celeryq.org/en/latest/internals/protocol.html
for more information.
The full contents of the message body was:
%s
Thw full contents of the message headers:
%s
The delivery info for this task is:
%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://docs.celeryq.org/en/latest/internals/protocol.html
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}}}
"""
TERMINATING_TASK_ON_RESTART_AFTER_A_CONNECTION_LOSS = """\
Task %s cannot be acknowledged after a connection loss since late acknowledgement is enabled for it.
Terminating it instead.
"""
CANCEL_TASKS_BY_DEFAULT = """
In Celery 5.1 we introduced an optional breaking change which
on connection loss cancels all currently executed tasks with late acknowledgement enabled.
These tasks cannot be acknowledged as the connection is gone, and the tasks are automatically redelivered back to the queue.
You can enable this behavior using the worker_cancel_long_running_tasks_on_connection_loss setting.
In Celery 5.1 it is set to False by default. The setting will be set to True by default in Celery 6.0.
""" # noqa: E501
[docs]def dump_body(m, body):
"""Format message body for debugging purposes."""
# v2 protocol does not deserialize body
body = m.body if body is None else body
return '{} ({}b)'.format(truncate(safe_repr(body), 1024),
len(m.body))
[docs]class Consumer:
"""Consumer blueprint."""
Strategies = dict
#: 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):
"""Consumer blueprint."""
name = 'Consumer'
default_steps = [
'celery.worker.consumer.connection:Connection',
'celery.worker.consumer.mingle:Mingle',
'celery.worker.consumer.events:Events',
'celery.worker.consumer.gossip:Gossip',
'celery.worker.consumer.heart:Heart',
'celery.worker.consumer.control:Control',
'celery.worker.consumer.tasks:Tasks',
'celery.worker.consumer.consumer:Evloop',
'celery.worker.consumer.agent: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 gethostname()
self.pid = os.getpid()
self.pool = pool
self.timer = timer
self.strategies = self.Strategies()
self.conninfo = self.app.connection_for_read()
self.connection_errors = self.conninfo.connection_errors
self.channel_errors = self.conninfo.channel_errors
self._restart_state = restart_state(maxR=5, maxT=1)
self._does_info = logger.isEnabledFor(logging.INFO)
self._limit_order = 0
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 or getattr(self.pool, 'is_green', False):
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._pending_operations = []
self.steps = []
self.blueprint = self.Blueprint(
steps=self.app.steps['consumer'],
on_close=self.on_close,
)
self.blueprint.apply(self, **dict(worker_options or {}, **kwargs))
[docs] def call_soon(self, p, *args, **kwargs):
p = ppartial(p, *args, **kwargs)
if self.hub:
return self.hub.call_soon(p)
self._pending_operations.append(p)
return p
[docs] def perform_pending_operations(self):
if not self.hub:
while self._pending_operations:
try:
self._pending_operations.pop()()
except Exception as exc: # pylint: disable=broad-except
logger.exception('Pending callback raised: %r', exc)
[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 self.app.tasks.items()
)
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.
:option:`--autoscale=1,0 <celery worker --autoscale>`).
"""
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_move_to_pool(self, request):
task_reserved(request)
self.on_task_request(request)
def _schedule_bucket_request(self, bucket):
while True:
try:
request, tokens = bucket.pop()
except IndexError:
# no request, break
break
if bucket.can_consume(tokens):
self._limit_move_to_pool(request)
continue
else:
# requeue to head, keep the order.
bucket.contents.appendleft((request, tokens))
pri = self._limit_order = (self._limit_order + 1) % 10
hold = bucket.expected_time(tokens)
self.timer.call_after(
hold, self._schedule_bucket_request, (bucket,),
priority=pri,
)
# no tokens, break
break
def _limit_task(self, request, bucket, tokens):
bucket.add((request, tokens))
return self._schedule_bucket_request(bucket)
def _limit_post_eta(self, request, bucket, tokens):
self.qos.decrement_eventually()
bucket.add((request, tokens))
return self._schedule_bucket_request(bucket)
[docs] def start(self):
blueprint = self.blueprint
while blueprint.state not in STOP_CONDITIONS:
maybe_shutdown()
if self.restart_count:
try:
self._restart_state.step()
except RestartFreqExceeded as exc:
crit('Frequent restarts detected: %r', exc, exc_info=1)
sleep(1)
self.restart_count += 1
try:
blueprint.start(self)
except self.connection_errors as exc:
# If we're not retrying connections, no need to catch
# connection errors
if not self.app.conf.broker_connection_retry:
raise
if isinstance(exc, OSError) and exc.errno == errno.EMFILE:
raise # Too many open files
maybe_shutdown()
if blueprint.state not in STOP_CONDITIONS:
if self.connection:
self.on_connection_error_after_connected(exc)
else:
self.on_connection_error_before_connected(exc)
self.on_close()
blueprint.restart(self)
[docs] def on_connection_error_before_connected(self, exc):
error(CONNECTION_ERROR, self.conninfo.as_uri(), exc,
'Trying to reconnect...')
[docs] def on_connection_error_after_connected(self, exc):
warn(CONNECTION_RETRY, exc_info=True)
try:
self.connection.collect()
except Exception: # pylint: disable=broad-except
pass
if self.app.conf.worker_cancel_long_running_tasks_on_connection_loss:
for request in tuple(active_requests):
if request.task.acks_late and not request.acknowledged:
warn(TERMINATING_TASK_ON_RESTART_AFTER_A_CONNECTION_LOSS,
request)
request.cancel(self.pool)
else:
warnings.warn(CANCEL_TASKS_BY_DEFAULT, CPendingDeprecationWarning)
[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.
Simply logs the error and acknowledges the message so it
doesn't enter a loop.
Arguments:
message (kombu.Message): The message received.
exc (Exception): The exception being handled.
"""
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()
for bucket in self.task_buckets.values():
if bucket:
bucket.clear_pending()
reserved_requests.clear()
if self.pool and self.pool.flush:
self.pool.flush()
[docs] def connect(self):
"""Establish the broker connection used for consuming tasks.
Retries establishing the connection if the
:setting:`broker_connection_retry` setting is enabled
"""
conn = self.connection_for_read(heartbeat=self.amqheartbeat)
if self.hub:
conn.transport.register_with_event_loop(conn.connection, self.hub)
return conn
[docs] def connection_for_read(self, heartbeat=None):
return self.ensure_connected(
self.app.connection_for_read(heartbeat=heartbeat))
[docs] def connection_for_write(self, heartbeat=None):
return self.ensure_connected(
self.app.connection_for_write(heartbeat=heartbeat))
[docs] def ensure_connected(self, conn):
# 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
next_step = next_step.format(
when=humanize_seconds(interval, 'in', ' '),
retries=int(interval / 2),
max_retries=self.app.conf.broker_connection_max_retries)
error(CONNECTION_ERROR, conn.as_uri(), exc, next_step)
# 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,
)
return conn
def _flush_events(self):
if self.event_dispatcher:
self.event_dispatcher.flush()
[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 :setting:`task_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)
signals.task_rejected.send(sender=self, message=message, exc=None)
[docs] def on_unknown_task(self, body, message, exc):
error(UNKNOWN_TASK_ERROR,
exc,
dump_body(message, body),
message.headers,
message.delivery_info,
exc_info=True)
try:
id_, name = message.headers['id'], message.headers['task']
root_id = message.headers.get('root_id')
except KeyError: # proto1
payload = message.payload
id_, name = payload['id'], payload['task']
root_id = None
request = Bunch(
name=name, chord=None, root_id=root_id,
correlation_id=message.properties.get('correlation_id'),
reply_to=message.properties.get('reply_to'),
errbacks=None,
)
message.reject_log_error(logger, self.connection_errors)
self.app.backend.mark_as_failure(
id_, NotRegistered(name), request=request,
)
if self.event_dispatcher:
self.event_dispatcher.send(
'task-failed', uuid=id_,
exception=f'NotRegistered({name!r})',
)
signals.task_unknown.send(
sender=self, message=message, exc=exc, name=name, id=id_,
)
[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)
signals.task_rejected.send(sender=self, message=message, exc=exc)
[docs] def update_strategies(self):
loader = self.app.loader
for name, task in self.app.tasks.items():
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, promise=promise):
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
call_soon = self.call_soon
def on_task_received(message):
# payload will only be set for v1 protocol, since v2
# will defer deserializing the message body to the pool.
payload = None
try:
type_ = message.headers['task'] # protocol v2
except TypeError:
return on_unknown_message(None, message)
except KeyError:
try:
payload = message.decode()
except Exception as exc: # pylint: disable=broad-except
return self.on_decode_error(message, exc)
try:
type_, payload = payload['task'], payload # protocol v1
except (TypeError, KeyError):
return on_unknown_message(payload, message)
try:
strategy = strategies[type_]
except KeyError as exc:
return on_unknown_task(None, message, exc)
else:
try:
strategy(
message, payload,
promise(call_soon, (message.ack_log_error,)),
promise(call_soon, (message.reject_log_error,)),
callbacks,
)
except (InvalidTaskError, ContentDisallowed) as exc:
return on_invalid_task(payload, message, exc)
except DecodeError as exc:
return self.on_decode_error(message, exc)
return on_task_received
def __repr__(self):
"""``repr(self)``."""
return '<Consumer: {self.hostname} ({state})>'.format(
self=self, state=self.blueprint.human_state(),
)
