"""Worker <-> Worker communication Bootstep."""
from collections import defaultdict
from functools import partial
from heapq import heappush
from operator import itemgetter
from kombu import Consumer
from kombu.asynchronous.semaphore import DummyLock
from kombu.exceptions import ContentDisallowed, DecodeError
from celery import bootsteps
from celery.utils.log import get_logger
from celery.utils.objects import Bunch
from .mingle import Mingle
__all__ = ('Gossip',)
logger = get_logger(__name__)
debug, info = logger.debug, logger.info
[документация]class Gossip(bootsteps.ConsumerStep):
"""Bootstep consuming events from other workers.
This keeps the logical clock value up to date.
"""
label = 'Gossip'
requires = (Mingle,)
_cons_stamp_fields = itemgetter(
'id', 'clock', 'hostname', 'pid', 'topic', 'action', 'cver',
)
compatible_transports = {'amqp', 'redis'}
def __init__(self, c, without_gossip=False,
interval=5.0, heartbeat_interval=2.0, **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.heartbeat_interval = heartbeat_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
}
super().__init__(c, **kwargs)
[документация] def compatible_transport(self, app):
with app.connection_for_read() as conn:
return conn.transport.driver_type in self.compatible_transports
[документация] def election(self, id, topic, action=None):
self.consensus_replies[id] = []
self.dispatcher.send(
'worker-elect',
id=id, topic=topic, action=action, cver=1,
)
[документация] def call_task(self, task):
try:
self.app.signature(task).apply_async()
except Exception as exc: # pylint: disable=broad-except
logger.exception('Could not call task: %r', exc)
[документация] def on_elect(self, event):
try:
(id_, clock, hostname, pid,
topic, action, _) = self._cons_stamp_fields(event)
except KeyError as exc:
return logger.exception('election request missing field %s', exc)
heappush(
self.consensus_requests[id_],
(clock, f'{hostname}.{pid}', topic, action),
)
self.dispatcher.send('worker-elect-ack', id=id_)
[документация] def start(self, c):
super().start(c)
self.dispatcher = c.event_dispatcher
[документация] def on_elect_ack(self, event):
id = event['id']
try:
replies = self.consensus_replies[id]
except KeyError:
return # not for us
alive_workers = set(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:
logger.exception('Unknown election topic %r', topic)
else:
handler(action)
else:
info('node %s elected for %r', leader, id)
self.consensus_requests.pop(id, None)
self.consensus_replies.pop(id, None)
[документация] def on_node_join(self, worker):
debug('%s joined the party', worker.hostname)
self._call_handlers(self.on.node_join, worker)
[документация] def on_node_leave(self, worker):
debug('%s left', worker.hostname)
self._call_handlers(self.on.node_leave, worker)
[документация] 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: # pylint: disable=broad-except
logger.exception(
'Ignored error from handler %r: %r', handler, exc)
[документация] def register_timer(self):
if self._tref is not None:
self._tref.cancel()
self._tref = self.timer.call_repeatedly(self.interval, self.periodic)
[документация] def periodic(self):
workers = self.state.workers
dirty = set()
for worker in workers.values():
if not worker.alive:
dirty.add(worker)
self.on_node_lost(worker)
for worker in dirty:
workers.pop(worker.hostname, None)
[документация] def get_consumers(self, channel):
self.register_timer()
ev = self.Receiver(channel, routing_key='worker.#',
queue_ttl=self.heartbeat_interval)
return [Consumer(
channel,
queues=[ev.queue],
on_message=partial(self.on_message, ev.event_from_message),
no_ack=True
)]
[документация] 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)
# proto2: hostname in header; proto1: in body
hostname = (message.headers.get('hostname') or
message.payload['hostname'])
if hostname != self.hostname:
try:
_, event = prepare(message.payload)
self.update_state(event)
except (DecodeError, ContentDisallowed, TypeError) as exc:
logger.error(exc)
else:
self.clock.forward()