in_tail: workaround "undeletable file" issue on Windows (#2141)

Windows will not actually delete a file as long as there is any
open handler for it. Until we close the last open handler, the
file is kept alive as "pending delete".

Obviously this has been breaking the log rotation mechanism for
some users. Work arount that by checking the "DeletePending" flag
manually in tail_fs_check().

Signed-off-by: Fujimoto Seiji <fujimoto@ceptord.net>

plugins/in_tail/tail_fs_stat.c

@@ -116,6 +116,26 @@ static int tail_fs_check(struct flb_input_instance *ins,
             continue;
         }
 
+#ifdef FLB_SYSTEM_WINDOWS
+        HANDLE h;
+        FILE_STANDARD_INFO info;
+
+        h = _get_osfhandle(file->fd);
+        if (GetFileInformationByHandleEx(h, FileStandardInfo,
+                                         &info, sizeof(info))) {
+            if (info.DeletePending) {
+                flb_plg_debug(ctx->ins, "file is to be delete: %s", file->name);
+#ifdef FLB_HAVE_SQLDB
+                if (ctx->db) {
+                    flb_tail_db_file_delete(file, ctx);
+                }
+#endif
+                flb_tail_file_remove(file);
+                continue;
+            }
+        }
+#endif
+
         /* Discover the current file name for the open file descriptor */
         name = flb_tail_file_name(file);
         if (!name) {