AMQPDaemon

This module provides generic AMQP daemon and builder of common connection informations, which are defined as constants in edeposit.amqp.settings.

Daemon is used by edeposit.amqp.alephdaemon and edeposit.amqp.calibredaemon.

class edeposit.amqp.amqpdaemon.AMQPDaemon(con_param, queue, out_exch, out_key, react_fn, glob)[source]

Bases: edeposit.amqp.pikadaemon.PikaDaemon

Parameters:
  • con_param (ConnectionParameters) – see getConParams() for details
  • queue (str) – name of the queue
  • out_exch (str) – name of the exchange for outgoing messages
  • out_key (str) – what key will be used to send messages back
  • react_fn (fn) – function, which can react to messages, see Note for details
  • glob (dict) – result of globals() call - used in deserializer to automatically build classes, which are not available in this namespace of this package

Note

react_fn parameter is expected to be function, which gets two parameters - message (some form of message, it can be also namedtuple), and UUID containing unique identificator of the message.

Example of function used as react_fn parameter:

def reactToAMQPMessage(message, UUID):
    response = None
    if message == 1:
        return 2
    elif message == "Hello":
        return "Hi"
    elif type(message) == dict:
        return {1: 2}

    raise UserWarning("Unrecognized message")

As you can see, protocol is pretty easy. You get message, to which you react somehow and return response. Thats all.

onMessageReceived(method_frame, properties, body)[source]

React to received message - deserialize it, add it to users reaction function stored in self.react_fn and send back result.

If Exception is thrown during process, it is sen’t back instead of message.

Note

In case of Exception, response message doesn’t have useful body, but in headers is stored this parameters: exception, where the Exception’s message is stored, exception_type, where e.__class__ is stored and exception_name, where e.__class__.__name__ is stored.

This allows you to react to unexpected cases at the other end of the AMQP communication.

edeposit.amqp.amqpdaemon.getConParams(virtualhost)[source]

Connection object builder.

Parameters:virtualhost (str) – selected virtualhost in rabbitmq
Returns:pika.ConnectionParameters – object filled by constants from edeposit.amqp.settings.

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