in_tail: Manage tail watchers under rorate_wait state

After a tail watcher transitions to `rotate_wait` state, the
`rotate_wait` timer is no longer managed by in_tail, it might cause
unexpected behaviour. e.g.)

* It's never unwatched when shutdown occurs before `rotate_wait` passed.
* Needless `rotate_wait` timers are executed when it detects more
  rotations.

This patch fixes such unexpected behaviour.

Signed-off-by: Takuro Ashie <ashie@clear-code.com>

lib/fluent/plugin/in_tail.rb

@@ -52,6 +52,7 @@ def initialize
       super
       @paths = []
       @tails = {}
+      @tails_rotate_wait = {}
       @pf_file = nil
       @pf = nil
       @ignore_list = []
@@ -267,6 +268,9 @@ def shutdown
       @shutdown_start_time = Fluent::Clock.now
       # during shutdown phase, don't close io. It should be done in close after all threads are stopped. See close.
       stop_watchers(existence_path, immediate: true, remove_watcher: false)
+      @tails_rotate_wait.each do |tw, data|
+        detach_watcher(tw, data[:ino])
+      end
       @pf_file.close if @pf_file
 
       super
@@ -582,7 +586,11 @@ def detach_watcher_after_rotate_wait(tw, ino)
       if @open_on_every_update
         # Detach now because it's already closed, waiting it doesn't make sense.
         detach_watcher(tw, ino)
-      elsif throttling_is_enabled?(tw)
+      end
+
+      return if @tails_rotate_wait[tw]
+
+      if throttling_is_enabled?(tw)
         # When the throttling feature is enabled, it might not reach EOF yet.
         # Should ensure to read all contents before closing it, with keeping throttling.
         start_time_to_wait = Fluent::Clock.now
@@ -591,13 +599,17 @@ def detach_watcher_after_rotate_wait(tw, ino)
           if tw.eof? && elapsed >= @rotate_wait
             timer.detach
             detach_watcher(tw, ino)
+            @tails_rotate_wait.delete(tw)
           end
         end
+        @tails_rotate_wait[tw] = { ino: ino, timer: timer }
       else
         # when the throttling feature isn't enabled, just wait @rotate_wait
-        timer_execute(:in_tail_close_watcher, @rotate_wait, repeat: false) do
+        timer = timer_execute(:in_tail_close_watcher, @rotate_wait, repeat: false) do
           detach_watcher(tw, ino)
+          @tails_rotate_wait.delete(tw)
         end
+        @tails_rotate_wait[tw] = { ino: ino, timer: timer }
       end
     end