This document describes the current stable version of Kombu (4.5). For development docs, go here.

Source code for kombu.mixins

# -*- coding: utf-8 -*-
"""Mixins."""
from __future__ import absolute_import, unicode_literals

import socket

from contextlib import contextmanager
from functools import partial
from itertools import count
from time import sleep

from .common import ignore_errors
from .five import range
from .messaging import Consumer, Producer
from .log import get_logger
from .utils.compat import nested
from .utils.encoding import safe_repr
from .utils.limits import TokenBucket
from .utils.objects import cached_property

__all__ = ('ConsumerMixin', 'ConsumerProducerMixin')

logger = get_logger(__name__)
debug, info, warn, error = (
    logger.debug,
    logger.info,
    logger.warning,
    logger.error
)

W_CONN_LOST = """\
Connection to broker lost, trying to re-establish connection...\
"""

W_CONN_ERROR = """\
Broker connection error, trying again in %s seconds: %r.\
"""


[docs]class ConsumerMixin(object): """Convenience mixin for implementing consumer programs. It can be used outside of threads, with threads, or greenthreads (eventlet/gevent) too. The basic class would need a :attr:`connection` attribute which must be a :class:`~kombu.Connection` instance, and define a :meth:`get_consumers` method that returns a list of :class:`kombu.Consumer` instances to use. Supporting multiple consumers is important so that multiple channels can be used for different QoS requirements. Example: .. code-block:: python class Worker(ConsumerMixin): task_queue = Queue('tasks', Exchange('tasks'), 'tasks') def __init__(self, connection): self.connection = None def get_consumers(self, Consumer, channel): return [Consumer(queues=[self.task_queue], callbacks=[self.on_task])] def on_task(self, body, message): print('Got task: {0!r}'.format(body)) message.ack() Methods: * :meth:`extra_context` Optional extra context manager that will be entered after the connection and consumers have been set up. Takes arguments ``(connection, channel)``. * :meth:`on_connection_error` Handler called if the connection is lost/ or is unavailable. Takes arguments ``(exc, interval)``, where interval is the time in seconds when the connection will be retried. The default handler will log the exception. * :meth:`on_connection_revived` Handler called as soon as the connection is re-established after connection failure. Takes no arguments. * :meth:`on_consume_ready` Handler called when the consumer is ready to accept messages. Takes arguments ``(connection, channel, consumers)``. Also keyword arguments to ``consume`` are forwarded to this handler. * :meth:`on_consume_end` Handler called after the consumers are canceled. Takes arguments ``(connection, channel)``. * :meth:`on_iteration` Handler called for every iteration while draining events. Takes no arguments. * :meth:`on_decode_error` Handler called if a consumer was unable to decode the body of a message. Takes arguments ``(message, exc)`` where message is the original message object. The default handler will log the error and acknowledge the message, so if you override make sure to call super, or perform these steps yourself. """ #: maximum number of retries trying to re-establish the connection, #: if the connection is lost/unavailable. connect_max_retries = None #: When this is set to true the consumer should stop consuming #: and return, so that it can be joined if it is the implementation #: of a thread. should_stop = False
[docs] def get_consumers(self, Consumer, channel): raise NotImplementedError('Subclass responsibility')
[docs] def on_connection_revived(self): pass
[docs] def on_consume_ready(self, connection, channel, consumers, **kwargs): pass
[docs] def on_consume_end(self, connection, channel): pass
[docs] def on_iteration(self): pass
[docs] def on_decode_error(self, message, exc): error("Can't decode message body: %r (type:%r encoding:%r raw:%r')", exc, message.content_type, message.content_encoding, safe_repr(message.body)) message.ack()
[docs] def on_connection_error(self, exc, interval): warn(W_CONN_ERROR, interval, exc, exc_info=1)
[docs] @contextmanager def extra_context(self, connection, channel): yield
[docs] def run(self, _tokens=1, **kwargs): restart_limit = self.restart_limit errors = (self.connection.connection_errors + self.connection.channel_errors) while not self.should_stop: try: if restart_limit.can_consume(_tokens): # pragma: no cover for _ in self.consume(limit=None, **kwargs): pass else: sleep(restart_limit.expected_time(_tokens)) except errors: warn(W_CONN_LOST, exc_info=1)
[docs] @contextmanager def consumer_context(self, **kwargs): with self.Consumer() as (connection, channel, consumers): with self.extra_context(connection, channel): self.on_consume_ready(connection, channel, consumers, **kwargs) yield connection, channel, consumers
[docs] def consume(self, limit=None, timeout=None, safety_interval=1, **kwargs): elapsed = 0 with self.consumer_context(**kwargs) as (conn, channel, consumers): for i in limit and range(limit) or count(): if self.should_stop: break self.on_iteration() try: conn.drain_events(timeout=safety_interval) except socket.timeout: conn.heartbeat_check() elapsed += safety_interval if timeout and elapsed >= timeout: raise except socket.error: if not self.should_stop: raise else: yield elapsed = 0 debug('consume exiting')
[docs] def maybe_conn_error(self, fun): """Use :func:`kombu.common.ignore_errors` instead.""" return ignore_errors(self, fun)
[docs] def create_connection(self): return self.connection.clone()
[docs] @contextmanager def establish_connection(self): with self.create_connection() as conn: conn.ensure_connection(self.on_connection_error, self.connect_max_retries) yield conn
[docs] @contextmanager def Consumer(self): with self.establish_connection() as conn: self.on_connection_revived() info('Connected to %s', conn.as_uri()) channel = conn.default_channel cls = partial(Consumer, channel, on_decode_error=self.on_decode_error) with self._consume_from(*self.get_consumers(cls, channel)) as c: yield conn, channel, c debug('Consumers canceled') self.on_consume_end(conn, channel) debug('Connection closed')
def _consume_from(self, *consumers): return nested(*consumers)
[docs] @cached_property def restart_limit(self): return TokenBucket(1)
[docs] @cached_property def connection_errors(self): return self.connection.connection_errors
[docs] @cached_property def channel_errors(self): return self.connection.channel_errors
[docs]class ConsumerProducerMixin(ConsumerMixin): """Consumer and Producer mixin. Version of ConsumerMixin having separate connection for also publishing messages. Example: .. code-block:: python class Worker(ConsumerProducerMixin): def __init__(self, connection): self.connection = connection def get_consumers(self, Consumer, channel): return [Consumer(queues=Queue('foo'), on_message=self.handle_message, accept='application/json', prefetch_count=10)] def handle_message(self, message): self.producer.publish( {'message': 'hello to you'}, exchange='', routing_key=message.properties['reply_to'], correlation_id=message.properties['correlation_id'], retry=True, ) """ _producer_connection = None
[docs] def on_consume_end(self, connection, channel): if self._producer_connection is not None: self._producer_connection.close() self._producer_connection = None
@property def producer(self): return Producer(self.producer_connection) @property def producer_connection(self): if self._producer_connection is None: conn = self.connection.clone() conn.ensure_connection(self.on_connection_error, self.connect_max_retries) self._producer_connection = conn return self._producer_connection