Sentinel: epoch introduced.
Sentinel: epoch introduced.

Sentinel state now includes the idea of current epoch and config epoch.
In the Hello message, that is now published both on masters and slaves,
a Sentinel no longer just advertises itself but also broadcasts its
current view of the configuration: the master name / ip / port and its
current epoch.

Sentinels receiving such information switch to the new master if the
configuration epoch received is newer and the ip / port of the master
are indeed different compared to the previos ones.

JackieXie168/redis,JackieXie168/redis,JackieXie168/redis,JackieXie168/redis