Redis cache avalanche

Cache avalanche ： Cache failure in a large area at the same time , The subsequent requests fall directly onto the database , Cause the database to bear a large number of requests in a short time .

It's like an avalanche , You can imagine the pressure of the database , It's possible that you've been knocked down by so many requests .

for instance ： There is something wrong with the cache module of the system, for example, it is unavailable due to downtime . Cause all access to the system , We have to go to the database . Then the pressure on the database soared , Request processing is not enough , Cause downtime .

terms of settlement

1、 in the light of Redis Service unavailability ：

1. use Redis Cluster and sentinel mode , To avoid problems on a single machine, the entire cache service cannot be used .
2. Current limiting , Avoid processing large amounts of requests at the same time .

2、 In case of hotspot cache failure ：

1. Set different expiration time, such as randomly setting cache expiration time . This is different key It will not expire at the same time , It will not cause a large amount of data to be inaccessible at one time .
2. Cache never fails .