Add docs and defaults for sending old event types

conf/minion

@@ -389,6 +389,16 @@
 # minion event bus. The value is expressed in bytes.
 #max_event_size: 1048576
 
+# When a minion starts up it sends a notification on the event bus with a tag
+# that looks like this: `salt/minion/<minion_id>/start`. For historical reasons
+# the minion also sends a similar event with an event tag like this:
+# `minion_start`. This duplication can cause a lot of clutter on the event bus
+# when there are many minions. Set `enable_legacy_startup_events: False` in the
+# minion config to ensure only the `salt/minion/<minion_id>/start` events are
+# sent. Beginning with the `Neon` Salt release this option will default to
+# `False`
+#enable_legacy_startup_events: True
+
 # To detect failed master(s) and fire events on connect/disconnect, set
 # master_alive_interval to the number of seconds to poll the masters for
 # connection events.

salt/config/__init__.py

@@ -433,6 +433,9 @@ VALID_OPTS = {
     # If an event is above this size, it will be trimmed before putting it on the event bus
     'max_event_size': int,
 
+    # Enable old style events to be sent on minion_startup. Change default to False in Neon release
+    'enable_legacy_startup_events': bool,
+
     # Always execute states with test=True if this flag is set
     'test': bool,
 
@@ -1360,6 +1363,7 @@ DEFAULT_MINION_OPTS = {
     'log_rotate_max_bytes': 0,
     'log_rotate_backup_count': 0,
     'max_event_size': 1048576,
+    'enable_legacy_startup_events': True,
     'test': False,
     'ext_job_cache': '',
     'cython_enable': False,