/usr/share/pyshared/pika/channel.py is in python-pika 0.9.5-1.
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#
# For copyright and licensing please refer to COPYING.
#
# ***** END LICENSE BLOCK *****
import types
import pika.frame as frame
import pika.exceptions as exceptions
import pika.log
import pika.spec as spec
MAX_CHANNELS = 32768
class ChannelTransport(object):
"""
The ChannelTransport class is meant to handle the communication paths to
and from the AMQP Broker. It is not supposed to implement client behavior
other than what is pre-specified by the Channel class. It is not meant
to be invoked by applications using Pika.
Note that as of RabbitMQ 2.0 Channel.Flow is no longer used and has been
removed and uses tcp backpressure instead. Since we only support 0-9-1
which was not introduced in RabbitMQ until 2.0, server side channel
flow detection has been removed.
"""
def __init__(self, connection, channel_number):
self.connection = connection
self.channel_number = channel_number
# Use the global callback handler
self.callbacks = connection.callbacks
# The frame-handler changes depending on the type of frame processed
self.frame_dispatcher = frame.Dispatcher(self.callbacks)
# We need to block on synchronous commands, but do so asynchronously
self.blocking = None
self._blocked = list()
# By default we're closed
self.closed = True
# Add callbacks for channel open event
self.callbacks.add(self.channel_number, spec.Channel.OpenOk,
self._on_open)
def _on_open(self, frame):
"""
Called as a result of receiving a spec.Channel.OpenOk frame.
"""
self.closed = False
def deliver(self, frame):
"""
Deliver a frame to the frame handler. When it's gotten to a point that
it has build our frame responses in a way we can use them, it will
call our callback stack to figure out what to do.
"""
self.frame_dispatcher.process(frame)
def _ensure(self):
"""
Make sure the transport is open
"""
if self.closed:
raise exceptions.ChannelClosed
return True
def _has_content(self, method):
"""
Return a bool if it's a content method as defined by the spec
"""
return spec.has_content(method.INDEX)
def rpc(self, method, callback=None, acceptable_replies=None):
"""
Shortcut wrapper to the Connection's rpc command using its callback
stack, passing in our channel number
"""
# Make sure the channel is open
self._ensure()
# If we're blocking, add subsequent commands to our stack
if self.blocking:
pika.log.debug('%s: %s is blocking this channel',
self.__class__.__name__, self.blocking)
self._blocked.append([method, callback, acceptable_replies])
return
# Validate we got None or a list of acceptable_replies
if acceptable_replies and not isinstance(acceptable_replies, list):
raise TypeError("acceptable_replies should be list or None")
# Validate the callback is a function or instancemethod
if callback and not isinstance(callback, types.FunctionType) and \
not isinstance(callback, types.MethodType):
raise TypeError("callback should be None, a function or method.")
# If this is a synchronous method, block connections until we're done
if method.synchronous:
pika.log.debug('%s: %s turning on blocking',
self.__class__.__name__, method.NAME)
self.blocking = method.NAME
if acceptable_replies:
for reply in acceptable_replies:
self.callbacks.add(self.channel_number, reply,
self._on_synchronous_complete)
if callback:
self.callbacks.add(self.channel_number, reply, callback)
self.send_method(method)
def send_method(self, method, content=None):
"""
Shortcut wrapper to send a method through our connection, passing in
our channel number
"""
self.connection._send_method(self.channel_number, method, content)
def _on_event_ok(self, frame):
"""
Generic events that returned ok that may have internal callbacks.
We keep a list of what we've yet to implement so that we don't silently
drain events that we don't support.
"""
pass
def _on_synchronous_complete(self, frame):
"""
This is called when a synchronous command is completed. It will undo
the blocking state and send all the frames that stacked up while we
were in the blocking state.
"""
# Release the lock
self.blocking = None
# Get the list, then empty it so we can spin through all the blocked
# Calls, blocking again in the class level list
blocked = self._blocked
self._blocked = list()
# Loop through and call all that were blocked during our last command
while blocked:
# Get the function to call next
method = blocked.pop(0)
# Call the RPC for each of our blocked calls
self.rpc(*method)
class Channel(spec.DriverMixin):
def __init__(self, connection, channel_number, on_open_callback=None,
transport=None):
"""
A Channel is the primary communication method for interacting with
RabbitMQ. It is recommended that you do not directly invoke
the creation of a channel object in your application code but rather
construct the a channel by calling the active connection's channel()
method.
"""
# Make sure that the caller passed in an int for the channel number
if not isinstance(channel_number, int):
raise exceptions.InvalidChannelNumber
# Get the handle to our transport, either passed in or made here
if transport:
self.transport = transport
else:
self.transport = ChannelTransport(connection, channel_number)
# Channel Number
self.channel_number = channel_number
# Get the callback manager
self.callbacks = connection.callbacks
# Our on_open_callback, special case
self._on_open_callback = on_open_callback
# Reason for closing channels
self.closing = None
# For event based processing
self._consumers = dict()
self._pending = dict()
# Set this here just as a default value
self._on_get_ok_callback = None
self._on_flow_ok_callback = None
# Add a callback for Basic.Deliver
self.callbacks.add(self.channel_number,
'_on_basic_deliver',
self._on_basic_deliver,
False,
frame.Dispatcher)
# Add a callback for Basic.Get
self.callbacks.add(self.channel_number,
'_on_basic_get',
self._on_basic_get_ok,
False,
frame.Dispatcher)
# Add a callback for Basic.GetEmpty
self.callbacks.add(self.channel_number,
spec.Basic.GetEmpty,
self._on_basic_get_empty,
False)
# Add a callback for when the server closes our channel
self.callbacks.add(self.channel_number,
spec.Channel.Close,
self._on_remote_close,
False)
# Add the callback for our Channel.OpenOk to call our on_open_callback
self.callbacks.add(self.channel_number,
spec.Channel.OpenOk,
self._open)
# Open our channel
self.transport.send_method(spec.Channel.Open())
def add_callback(self, callback, replies):
"""
Pass in a callback handler and a list replies from the
RabbitMQ broker which you'd like the callback notified of. Callbacks
should allow for the frame parameter to be passed in.
"""
for reply in replies:
self.callbacks.add(self.channel_number, reply, callback)
def add_on_close_callback(self, callback):
"""
Pass a callback function that will be called when the channel is
closed. The callback function should receive a frame parameter.
"""
self.callbacks.add(self.channel_number, '_on_channel_close', callback)
def add_on_return_callback(self, callback):
"""
Pass a callback function that will be called when basic_publish as sent
a message that has been rejected and returned by the server. The
callback handler should receive a method, header and body frame. The
base signature for the callback should be the same as the method
signature one creates for a basic_consume callback.
"""
self.callbacks.add(self.channel_number, '_on_basic_return', callback)
def close(self, code=0, text="Normal Shutdown", from_server=False):
"""
Will invoke a clean shutdown of the channel with the AMQP Broker
"""
# Set our closing code and text
self.closing = code, text
# Let an application that registered itself our callbacks know we're
# Closing/Closed
self.callbacks.process(self.channel_number, '_on_channel_close',
self, code, text)
# Send our basic cancel for all of our consumers
for consumer_tag in self._consumers.keys():
self.basic_cancel(consumer_tag)
# If we have an open connection send a RPC call to close the channel
if not len(self._consumers) and not from_server:
self._close()
def _close(self):
"""
Internal close, is called when all the consumers are closed by both
Channel.close and Channel._on_cancel_ok
"""
self.transport.send_method(spec.Channel.Close(self.closing[0],
self.closing[1],
0, 0))
def _on_remote_close(self, frame):
"""
Handle the case where our channel has been closed for us
"""
# Set our closing code and text
self.closing = frame.method.reply_code, frame.method.reply_text
# Let an application that registered itself our callbacks know we're
# Closing/Closed
self.callbacks.process(self.channel_number, '_on_channel_close',
self, frame.method.reply_code,
frame.method.reply_text)
def _open(self, frame):
"""
Called by our callback handler when we receive a Channel.OpenOk and
subsequently calls our _on_open_callback which was passed into the
Channel constructor. The reason we do this is because we want to make
sure that the on_open_callback parameter passed into the Channel
constructor is not the first callback we make. ChannelTransport needs
to know before the app that passed in the callback.
"""
# Call our on open callback
if self._on_open_callback:
self._on_open_callback(self)
def basic_cancel(self, consumer_tag, nowait=False, callback=None):
"""
Pass in the consumer tag to cancel a basic_consume request with. The
consumer_tag is optionally passed to basic_consume as a parameter and
it is always returned by the Basic.ConsumeOk frame. For more
information see:
http://www.rabbitmq.com/amqp-0-9-1-reference.html#basic.cancel
"""
if consumer_tag not in self._consumers:
return
if callback:
self.callbacks.add(self.channel_number,
spec.Basic.CancelOk,
callback)
# Send a Basic.Cancel RPC call to close the Basic.Consume
self.transport.rpc(spec.Basic.Cancel(consumer_tag=consumer_tag,
nowait=nowait),
self._on_cancel_ok, [spec.Basic.CancelOk])
def basic_consume(self, consumer_callback,
queue='', no_ack=False, exclusive=False,
consumer_tag=None):
"""
Sends the AMQP command Basic.Consume to the broker and binds messages
for the consumer_tag to the consumer callback. If you do not pass in
a consumer_tag, one will be automatically generated for you. Returns
the consumer tag.
For more information on basic_consume, see:
http://www.rabbitmq.com/amqp-0-9-1-reference.html#basic.consume
"""
# If a consumer tag was not passed, create one
if not consumer_tag:
consumer_tag = 'ctag%i' % len(self._consumers)
# Make sure we've not already registered this consumer tag
if consumer_tag in self._consumers:
raise exceptions.DuplicateConsumerTag(consumer_tag)
# The consumer tag has not been used before, add it to our consumers
self._consumers[consumer_tag] = consumer_callback
# Send our Basic.Consume RPC call
try:
self.transport.rpc(spec.Basic.Consume(queue=queue,
consumer_tag=consumer_tag,
no_ack=no_ack,
exclusive=exclusive),
self.transport._on_event_ok,
[spec.Basic.ConsumeOk])
except exceptions.ChannelClosed, e:
del(self._consumers[consumer_tag])
raise exceptions.ChannelClosed(e)
# Return the consumer tag for the user reference
return consumer_tag
def basic_publish(self, exchange, routing_key, body,
properties=None, mandatory=False, immediate=False):
"""
Publish to the channel with the given exchange, routing key and body.
For more information on basic_publish and what the parameters do, see:
http://www.rabbitmq.com/amqp-0-9-1-reference.html#basic.publish
"""
# If properties are not passed in, use the spec's default
properties = properties or spec.BasicProperties()
self.transport.send_method(spec.Basic.Publish(exchange=exchange,
routing_key=routing_key,
mandatory=mandatory,
immediate=immediate),
(properties, body))
@property
def consumer_tags(self):
"""
Property method that returns a list of currently active consumers
"""
return self._consumers.keys()
def _on_basic_deliver(self, method_frame, header_frame, body):
"""
Cope with reentrancy. If a particular consumer is still active when
another delivery appears for it, queue the deliveries up until it
finally exits.
"""
# Shortcut for our consumer tag
consumer_tag = method_frame.method.consumer_tag
# If we don't have anything pending,
if consumer_tag not in self._pending and \
consumer_tag in self._consumers:
# Setup a list for appending frames into
self._pending[consumer_tag] = list()
# Call our consumer callback with the data
self._consumers[consumer_tag](self,
method_frame.method,
header_frame.properties,
body)
# Loop through and empty the list, we may have gotten more
# while we were delivering the message to the callback
while self._pending[consumer_tag]:
# Remove the parts of our list item
(method, properties, body) = self._pending[consumer_tag].pop(0)
# Call our consumer callback with the data
self._consumers[consumer_tag](self,
method,
properties,
body)
# Remove our pending messages
del self._pending[consumer_tag]
else:
# Append the message to our pending list
self._pending[consumer_tag].append((method_frame.method,
header_frame.properties,
body))
def _on_cancel_ok(self, frame):
"""
Called in response to a frame from the Broker when we call Basic.Cancel
"""
# We need to delete the consumer tag from our _consumers
del(self._consumers[frame.method.consumer_tag])
# If we're closing and dont have any consumers left, close
if self.closing and not len(self._consumers):
self._close()
def basic_get(self, callback, ticket=0, queue='', no_ack=False):
"""
Get a single message from the AMQP broker. The callback method
signature should have 3 parameters: The method frame, header frame and
the body, like the consumer callback for Basic.Consume. If you want to
be notified of Basic.GetEmpty, use the Channel.add_callback method
adding your Basic.GetEmpty callback which should expect only one
parameter, frame. For more information on basic_get and its
parameters, see:
http://www.rabbitmq.com/amqp-0-9-1-reference.html#basic.get
"""
self._on_get_ok_callback = callback
self.transport.send_method(spec.Basic.Get(ticket=ticket,
queue=queue,
no_ack=no_ack))
def _on_basic_get_ok(self, method_frame, header_frame, body):
if self._on_get_ok_callback:
self._on_get_ok_callback(self,
method_frame.method,
header_frame.properties,
body)
self._basic_get_ok_callback = None
else:
pika.log.error("%s._on_basic_get: No callback defined.",
self.__class__.__name__)
def _on_basic_get_empty(self, frame):
"""
When we receive an empty reply do nothing but log it
"""
pass
def flow(self, callback, active):
"""
Turn Channel flow control off and on. Pass a callback to be notified
of the response from the server. active is a bool. Callback should
expect a bool in response indicating channel flow state. For more
information, please reference:
http://www.rabbitmq.com/amqp-0-9-1-reference.html#channel.flow
"""
self._on_flow_ok_callback = callback
self.transport.rpc(spec.Channel.Flow(active), self._on_channel_flow_ok,
[spec.Channel.FlowOk])
def _on_channel_flow_ok(self, frame):
"""
Called in response to us asking the server to toggle on Channel.Flow
"""
# Update the channel flow_active state
self.transport.flow_active = frame.method.active
# If we have a callback defined, process it
if self._on_flow_ok_callback:
self._on_flow_ok_callback(frame.method.active)
self._on_flow_ok_callback = None
else:
pika.log.error("%s._on_flow_ok: No callback defined.",
self.__class__.__name__)
def confirm_delivery(self, callback=None, nowait=False):
"""
Turn on Confirm mode in the channel. Pass in a callback to be notified
by the Broker when a message has been confirmed as received (Basic.Ack
from the broker to the publisher).
For more information see:
http://www.rabbitmq.com/extensions.html#confirms
"""
# Add the Basic.Ack callback
if callback:
self.callbacks.add(self.channel_number,
spec.Basic.Ack,
callback,
False)
# Send the RPC command
self.transport.rpc(spec.Confirm.Select(nowait),
self._on_confirm_select_ok,
[spec.Confirm.SelectOk])
def _on_confirm_select_ok(self, frame):
"""
Called when the broker sends a Confirm.SelectOk frame
"""
pika.log.info("Confirm.SelectOk Received")
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