Last mutation is always delayed several minutes to be shipped to the remote cluster during duplication

[empiredan]

While testing duplication, there's always the last mutation. The last mutation means that, after this mutation, there's not any mutation written into the source cluster.

The problem is that the last mutation would not be duplicated to the remote cluster; instead, it always takes 2 ~ 3 minutes to duplicate the last mutation to the remote cluster. To be exact, the process of duplicating itself is fast; we have to waits 2 ~ 3 minutes (until some empty write gets in) before it is duplicated to the remote cluster.