Using the Open edX Event bus
============================

After creating a new Open edX Event, you might need to send it across services
instead of just within the same process. For this kind of use-cases, you might want
to use the Open edX Event Bus. Here, we list useful information about
adding a new event to the event bus:

- `How to start using the Event Bus`_


.. _How to start using the Event Bus: https://openedx.atlassian.net/wiki/spaces/AC/pages/3508699151/How+to+start+using+the+Event+Bus


Producing to event bus
^^^^^^^^^^^^^^^^^^^^^^

In the producing/host application, include ``openedx_events`` in ``INSTALLED_APPS`` settings and add ``EVENT_BUS_PRODUCER_CONFIG`` setting. For example, below snippet is to push ``XBLOCK_PUBLISHED`` to two different topics and ``XBLOCK_DELETED`` signal to one topic in event bus.

.. code-block:: python

   # .. setting_name: EVENT_BUS_PRODUCER_CONFIG
   # .. setting_default: {}
   # .. setting_description: Dictionary of event_types mapped to lists of dictionaries containing topic related configuration.
   #    Each topic configuration dictionary contains
   #    * a topic/stream name called `topic` where the event will be pushed to.
   #    * a flag called `enabled` denoting whether the event will be published to the topic.
   #    * `event_key_field` which is a period-delimited string path to event data field to use as event key.
   #    Note: The topic names should not include environment prefix as it will be dynamically added based on
   #    EVENT_BUS_TOPIC_PREFIX setting.
   EVENT_BUS_PRODUCER_CONFIG = {
       'org.openedx.content_authoring.xblock.published.v1': [
           {'topic': 'content-authoring-xblock-lifecycle', 'event_key_field': 'xblock_info.usage_key', 'enabled': True},
           {'topic': 'content-authoring-xblock-published', 'event_key_field': 'xblock_info.usage_key', 'enabled': True},
       ],
       'org.openedx.content_authoring.xblock.deleted.v1': [
           {'topic': 'content-authoring-xblock-lifecycle', 'event_key_field': 'xblock_info.usage_key', 'enabled': True},
       ],
   }

The ``EVENT_BUS_PRODUCER_CONFIG`` is read by openedx_events and a handler is attached which does the leg work of reading the configuration again and pushing to appropriate handlers.