.. currentmodule:: event_collector.messagebus


Message Bus
===========

**Source code:** `event_collector.messagebus.py`

.. py:module:: event_collector.messagebus

   This module implements a message bus used internally between the CollectorQueue and other components.

.. pull-quote::

   The *MessageBus* allows one component of the event-collector system to listen to messages
   or *bus events* emitted by other components without explicit tight coupling.


MessageBus classes
------------------

.. autoclass:: event_collector.messagebus.Message

   ``Message`` is a generic base class for a bus message.

.. autoclass:: event_collector.messagebus.Command

   ``Command`` is a generic base class for a bus command.

.. autoclass:: event_collector.messagebus.MessageBus

   The message bus works by dispatching messages or commands to handlers.

   A ``MessageBus`` instance is initialized with a set of ``MsgHandlers`` and ``CmdHandlers``.

   Components define subclasses of ``Message`` or ``Command`` and
   dispatch or publish these events through the message bus. For each
   message or command, the message bus will check if any message or
   command handlers are registered to listen to the events. If a
   handler is registered, the bus will call the handler function when
   the message or command is triggered by the "dispatch" method.

   The ``CollectorQueue`` emits a set of ``Messages`` that your application
   can listen to. These are documented in the (:py:mod:`~event_collector.queue`) module.