Use message_length_limit to unify parameter name between plugins

lib/fluent/plugin/in_udp.rb

@@ -34,7 +34,10 @@ class UdpInput < Input
     desc "The field name of the client's hostname."
     config_param :source_hostname_key, :string, default: nil
 
-    config_param :body_size_limit, :size, default: 4096
+    desc "Deprecated parameter. Use message_length_limit instead"
+    config_param :body_size_limit, :size, default: nil, deprecated: "use message_length_limit instead."
+    desc "The max bytes of message"
+    config_param :message_length_limit, :size, default: 4096
 
     config_param :blocking_timeout, :time, default: 0.5
 
@@ -43,6 +46,7 @@ def configure(conf)
       super
       @_event_loop_blocking_timeout = @blocking_timeout
       @source_hostname_key ||= @source_host_key if @source_host_key
+      @message_length_limit = @body_size_limit if @body_size_limit
 
       @parser = parser_create
     end
@@ -55,7 +59,7 @@ def start
       super
 
       log.info "listening udp socket", bind: @bind, port: @port
-      server_create(:in_udp_server, @port, proto: :udp, bind: @bind, max_bytes: @body_size_limit) do |data, sock|
+      server_create(:in_udp_server, @port, proto: :udp, bind: @bind, max_bytes: @message_length_limit) do |data, sock|
         data.chomp!
         begin
           @parser.parse(data) do |time, record|

test/plugin/test_in_udp.rb

@@ -54,7 +54,7 @@ def create_udp_socket(host, port)
     d = create_driver(conf)
     assert_equal PORT, d.instance.port
     assert_equal bind, d.instance.bind
-    assert_equal 4096, d.instance.body_size_limit
+    assert_equal 4096, d.instance.message_length_limit
   end
 
   data(
@@ -86,6 +86,16 @@ def create_udp_socket(host, port)
     end
   end
 
+  data(
+    'message_length_limit' => 'message_length_limit 2048',
+    'body_size_limit' => 'body_size_limit 2048'
+  )
+  test 'message_length_limit/body_size_limit compatibility' do |param|
+
+    d = create_driver(CONFIG + param)
+    assert_equal 2048, d.instance.message_length_limit
+  end
+
   data(
     'none' => {
       'format' => 'none',