Redis Failover Process

Before leader triggers failover, wait a few seconds (then 0~5) for other Sentinel instances to prepare and adjust. If all is well, then leader needs to start upgrading a salve to master, which must be in a good state (not in the Sdown/odown state) and with the lowest weight value (redis.conf), when Master is confirmed, Start failover

A) "+failover-triggered": Leader began failover, followed by "+failover-state-wait-start", wait for a few seconds.

B) "+failover-state-select-slave": Leader start looking for the right slave

C) "+selected-slave": a suitable slave has been found

D) "+failover-state-sen-slaveof-noone": Leader sends the "slaveof no one" instruction to Slave, at which point Slave has completed the role conversion, this slave is the master

E) "+failover-state-wait-promotition": Wait for other Sentinel confirmation slave

F) "+promoted-slave": Confirm success

G) "+failover-state-reconf-slaves": Start the reconfig operation on the slaves.

H) "+slave-reconf-sent": Sends the "slaveof" instruction to the specified slave, informing the slave to follow the new master

I) "+slave-reconf-inprog": This slave is performing the slaveof + sync process, +slave-reconf-sent will be performed after slave receives "slaveof".

J) "+slave-reconf-done": This slave completes synchronously, and thereafter leader can continue the reconfig operation of the next slave. Cycle g)

K) "+failover-end": End of failover

L) "+switch-master": After a successful failover, each Sentinel instance starts to monitor the new master.

Redis Failover Process