Raft算法以超半数写入即确认保存成功, 那如果访问的正好是没写入那个节点,怎么保证一致

问题 就是说强一致性被破坏了

• Raft算法以超半数写入即确认保存成功, 那如果访问的正好是没写入那个节点,怎么保证一致 ？

首先分布式系统的前提是CAP理论

CAP理论

• P Partition tolerance 分区容错性
  • 分布式多个服务 位于不同服务器 可能之间会失败
• C Consistency 一致性
  • 写入或者更新数据后，必须读取必须返回这个写入或者更新的值
• A Availability 可用性
  • 就是啥时候访问必须给响应 基于reuqust/response

P 天然会使用

• 网络是不可靠的，因此分区容错任何时候都无法避免 P总是成立

raft 论文

5.1 Raft basics
A Raft cluster contains several servers; five is a typical number, which allows the system to tolerate two failures. At any given time each server is in one of three states: leader, follower, or candidate. In normal operation there is exactly one leader and all of the other servers are fol- lowers. Followers are passive: they issue no requests on their own but simply respond to requests from leaders and candidates. The leader handles all client requests (if a client contacts a follower, the follower redirects it to the leader). The third state, candidate, is used to elect a new leader as described in Section 5.2. Figure 4 shows the states and their transitions; the transitions are discussed below.

• 大意是讲 就算你把请求发给follower 一样会转发leaderc处理

真像就是 raft是强leader模式

• 任何请求只能是leader 来处理，就算你发给follewer 一样是leader处理
• 所以问题本身就是不成立