Skip the refresh of watching list on startup.

lib/fluent/plugin/in_tail.rb

@@ -79,6 +79,8 @@ def initialize
     config_param :open_on_every_update, :bool, default: false
     desc 'Limit the watching files that the modification time is within the specified time range (when use \'*\' in path).'
     config_param :limit_recently_modified, :time, default: nil
+    desc 'Enable the option to skip the refresh of watching list on startup.'
+    config_param :skip_refresh_on_startup, :bool, default: false
 
     attr_reader :paths
 
@@ -160,7 +162,7 @@ def start
         @pf = PositionFile.parse(@pf_file)
       end
 
-      refresh_watchers
+      refresh_watchers unless @skip_refresh_on_startup
       timer_execute(:in_tail_refresh_watchers, @refresh_interval, &method(:refresh_watchers))
     end
 

test/plugin/test_in_tail.rb

@@ -1198,4 +1198,19 @@ def test_limit_recently_modified
       assert_equal expected_files, plugin.expand_paths.sort
     end
   end
+
+  def test_skip_refresh_on_startup
+    FileUtils.touch("#{TMP_DIR}/tail.txt")
+    config = config_element('', '', {
+                              'format' => 'none',
+                              'refresh_interval' => 1,
+                              'skip_refresh_on_startup' => true
+                            })
+    d = create_driver(config)
+    d.run(shutdown: false) {}
+    assert_equal 0, d.instance.instance_variable_get(:@tails).keys.size
+    # detect a file at first execution of in_tail_refresh_watchers timer
+    waiting(5) { sleep 0.1 until d.instance.instance_variable_get(:@tails).keys.size == 1 }
+    d.instance_shutdown
+  end
 end