經查看redis 配置了五個節點，後來下線兩個redis,但是sentinel依然顯示五個節點，但是兩個節點顯示下線，但是sentinel依然每隔一秒鐘去探測下線的服務器，此問題是sentinel的bug參見官方文檔，在3.0.2中已經修復
* [FIX] Resolved a memoryleak in the hiredis library causing a memory leak
in Redis Sentinel when a monitored instance or another Sentinel is
unavailable. Every reconnection attempt will leak a small amount of
memory, but in the long run the process can reach a considerable size.
具體見redisReleaseNotes
--[ Redis 3.0.0 RC1 (version 2.9.101) ] Release date: 9 oct 2014
https://raw.githubusercontent.com/antirez/redis/3.0/00-RELEASENOTES