Distributed cache architecture - cache avalanche & penetration & hit rate

Cache penetration and cache avalanche

Cache avalanche

The cause of cache avalanche

Cache avalanche is simply understood as ： Due to the original cache failure （ Or the data is not loaded into the cache ）, Period before new cache （ Cache normally from Redis In order to get , Here's the picture ） All requests that should have access to the cache are going to query the database , And for databases CPU And memory , Serious will cause database downtime , Cause the system to crash .

When the cache fails, see the figure below ：