http://www.jianshu.com/p/6e60c5696089
http://www.jianshu.com/p/4711c4c32aab
https://github.com/maemual/raft-zh_cn/blob/master/raft-zh_cn.md
http://blog.itpub.net/28944233/viewspace-1777786/
正常操作流程:
1. Client发送command给Leader
2. Leader追加command至本地log
3. Leader广播AppendEntriesRPC至Follower
4. 一旦日志项committed成功:
1) Leader应用对应的command至本地StateMachine,并返回结果至Client
2) Leader通过后续AppendEntriesRPC将committed日志项通知到Follower
3) Follower收到committed日志项后,将其应用至本地StateMachine