5. When I set the exception key in the bucket by manual, the ops is also up to 1.1k/s, and then delete it from bucket, the ops also not down;
I had investigated the situation before the question posted that.
1. The application has no such reading or writing log about the key, while other keys can be found.
2. I logined to the exception node(192.168.250.174) and got the network connection of the port 11209~11213, there is no other application connect to the port except my application.
As what I said in the last comment, I failed over the node(192.168.250.174) , and the execption node changed to another node(192.168.250.154), while the exception key also changed to another.