docs: improve docstrings for handlers and new events routers

event_routing_backends/backends/async_events_router.py

@@ -1,5 +1,8 @@
 """
-Generic async router to send events to hosts via celery.
+Events router to send events to hosts via celery.
+
+This events router will trigger a celery task to send the events to the
+configured hosts.
 """
 from event_routing_backends.backends.events_router import EventsRouter
 from event_routing_backends.tasks import dispatch_bulk_events, dispatch_event, dispatch_event_persistent

event_routing_backends/backends/events_router.py

@@ -23,7 +23,6 @@ def __init__(self, processors=None, backend_name=None):
         Arguments:
             processors (list):   list of processor instances
             backend_name (str):  name of the router backend
-            sync (bool):         whether to send events synchronously or in celery tasks
         """
         self.processors = processors if processors else []
         self.backend_name = backend_name

event_routing_backends/backends/sync_events_router.py

@@ -1,13 +1,17 @@
 """
-Generic router to send events to hosts.
+Events router to send events to hosts in sync mode.
+
+This router is expected to be used with the event bus, which
+can be configured to use this router to send events to hosts
+in the same thread as it process the events.
 """
 from event_routing_backends.backends.events_router import EventsRouter
 from event_routing_backends.tasks import bulk_send_events, send_event
 
 
 class SyncEventsRouter(EventsRouter):
     """
-    Router to send events to hosts via celery using requests library.
+    Router to send events to hosts using requests library.
     """
 
     def dispatch_event(self, event_name, updated_event, router_type, host_configurations):

event_routing_backends/handlers.py

@@ -19,6 +19,18 @@ def send_tracking_log_to_backends(
 ):  # pylint: disable=unused-argument
     """
     Listen for the TRACKING_LOG_EVENT_EMITTED signal and send the event to the enabled backends.
+
+    The process is the following:
+
+    1. Unserialize the tracking log from the signal.
+    2. Get the tracker instance to get the enabled backends (mongo, event_bus, logger, etc).
+    3. Get the event bus backends as those are the interested in the signals and multiple can be configured.
+    4. Process the event with the event bus backend.
+    5. Send the processed event to the different event bus backends configured. Any event bus backend can be configured
+    with multiples backends (xAPI or Caliper).
+
+    This allows us to only send the tracking log to the event bus once and then the event bus will send it to the
+    different configured backends.
     """
     tracking_log = kwargs.get("tracking_log")
 

event_routing_backends/settings/common.py

@@ -60,8 +60,6 @@ def plugin_settings(settings):
         'edx.course.grade.passed.first_time'
     ]
 
-    settings.EVENT_TRACKING_BACKENDS_EVENT_BUS_ENABLED = True
-
     settings.WHITELIST_EVENTS = {
         'xapi': [
             'edx.course.enrollment.activated',