Merge pull request #4940 from dedemorton/add_udp_prospector

[Docs] Add udp prospector to list of types

filebeat/docs/filebeat-options.asciidoc

@@ -32,9 +32,10 @@ filebeat.prospectors:
 
 One of the following input types:
 
-    * log: Reads every line of the log file (default)
-    * stdin: Reads the standard in
-    * redis: Reads slow log entries from redis (experimental)
+    * log: Reads every line of the log file (default).
+    * stdin: Reads the standard in.
+    * redis: Reads slow log entries from redis (experimental).
+    * udp: Reads events over UDP. Also see <<max-message-size>>.
 
 The value that you specify here is used as the `type` for each event published to Logstash and Elasticsearch.
 
@@ -492,3 +493,9 @@ by assigning a higher limit of harvesters.
 
 The `enabled` option can be used with each prospector to define if a prospector is enabled or not. By default, enabled is set to true.
 
+[float]
+[[max-message-size]]
+==== `max_message_size`
+
+When used with `type: udp`, specifies the maximum size of the message received over UDP. The default is 10240.
+