in_tail: Fix log duplication when follow_inode is true

There are 2 causes on this issue:

* Wrong inode is set to TailWatcher when follow_inode is true
* A key (TargetInfo) in @Tails isn't updated for a same path even if new
  one has different inode

Fix #3464

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

lib/fluent/plugin/in_tail.rb

@@ -426,6 +426,7 @@ def construct_watcher(target_info)
 
       begin
         target_info = TargetInfo.new(target_info.path, Fluent::FileWrapper.stat(target_info.path).ino)
+        @tails.delete(target_info)
         @tails[target_info] = tw
         tw.on_notify
       rescue Errno::ENOENT, Errno::EACCES => e
@@ -491,10 +492,17 @@ def update_watcher(target_info, pe)
         new_position_entry = @pf[target_info]
 
         if new_position_entry.read_inode == 0
+          # When follow_inodes is true, it's not cleaned up by refresh_watcher.
+          # So it should be unwatched here explicitly.
+          rotated_tw.unwatched = true
+          # Make sure to delete old key, it has a different ino while the hash key is same.
+          @tails.delete(rotated_target_info)
           @tails[new_target_info] = setup_watcher(new_target_info, new_position_entry)
           @tails[new_target_info].on_notify
         end
       else
+        # Make sure to delete old key, it has a different ino while the hash key is same.
+        @tails.delete(rotated_target_info)
         @tails[new_target_info] = setup_watcher(new_target_info, pe)
         @tails[new_target_info].on_notify
       end
@@ -831,7 +839,7 @@ def on_rotate(stat)
               # new watcher, and old watcher will be closed by stop_watcher in refresh_watchers method
               # don't want to swap state because we need latest read offset in pos file even after rotate_wait
               if stat
-                target_info = TargetInfo.new(@path, stat)
+                target_info = TargetInfo.new(@path, stat.ino)
                 @update_watcher.call(target_info, @pe)
               end
             else

test/plugin/test_in_tail.rb

@@ -109,6 +109,7 @@ def create_target_info(path)
                                                 "refresh_interval" => "1s",
                                                 "read_from_head" => "true",
                                                 "format" => "none",
+                                                "rotate_wait" => "1s",
                                                 "follow_inodes" => "true"
                                               })
   SINGLE_LINE_CONFIG = config_element("", "", { "format" => "/(?<message>.*)/" })