Mixin Classes - kombu.mixins

kombu.mixins

Useful mixin classes.

copyright:

3. 2009 - 2012 by Ask Solem.

license:

BSD, see LICENSE for more details.

class kombu.mixins.ConsumerMixin

Convenience mixin for implementing consumer threads.

It can be used outside of threads, with threads, or greenthreads (eventlet/gevent) too.

The basic class would need a connection attribute which must be a BrokerConnection instance, and define a get_consumers() method that returns a list of kombu.messaging.Consumer instances to use. Supporting multiple consumers is important so that multiple channels can be used for different QoS requirements.

Example:

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],
                         callback=[self.on_task])]

    def on_task(self, body, message):
        print("Got task: %r" % (body, ))
        message.ack()

Additional handler methods:

• extra_context()

  Optional extra context manager that will be entered after the connection and consumers have been set up.

  Takes arguments (connection, channel).

• 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.

• on_connection_revived()

  Handler called when the connection is re-established after connection failure.

  Takes no arguments.

• 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.

• on_consume_end()

  Handler called after the consumers are cancelled. Takes arguments (connection, channel).

• on_iteration()

  Handler called for every iteration while draining events.

  Takes no arguments.

• 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.

Consumer(*args, **kwds)

channel_errors

connect_max_retries = None

maximum number of retries trying to re-establish the connection, if the connection is lost/unavailable.

connection_errors

consume(limit=None, timeout=None, safety_interval=1, **kwargs)

establish_connection(*args, **kwds)

extra_context(*args, **kwds)

get_consumers(Consumer, channel)

maybe_conn_error(fun)

Applies function but ignores any connection or channel errors raised.

on_connection_error(exc, interval)

on_connection_revived()

on_consume_end(connection, channel)

on_consume_ready(connection, channel, consumers, **kwargs)

on_decode_error(message, exc)

on_iteration()

restart_limit

run()

should_stop = False

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.