in_forward: Seek more opprtunity to optimize

Signed-off-by: Hiroshi Hatake <hiroshi@chronosphere.io>

Author: cosmo0920

lib/fluent/plugin/in_forward.rb

@@ -68,6 +68,7 @@ def each(unpacker: nil, &block)
     helpers :server
 
     LISTEN_PORT = 24224
+    OPTION_FLUENT_SIGNAL = 'fluent_signal'.freeze
 
     desc 'The port to listen to.'
     config_param :port, :integer, default: LISTEN_PORT
@@ -354,13 +355,11 @@ def on_message(msg, chunk_size, conn)
         else
           es = Fluent::MessagePackEventStream.new(entries, nil, size.to_i)
         end
-        es = if @skip_invalid_event
-               normalize_event_stream(tag, es, conn.remote_host)
-             elsif option['fluent_signal'] == 0
-               MetadataTimeEventStream.new(es)
-             else
-               es
-             end
+        if @skip_invalid_event
+          es = normalize_event_stream(tag, es, conn.remote_host)
+        elsif option[OPTION_FLUENT_SIGNAL] == 0
+          es = MetadataTimeEventStream.new(es)
+        end
         if @enable_field_injection
           es = add_source_info(es, conn)
         end