In terms of cache stability, basically, every cache-related article and share on the web talks about three key points.

• Cache penetration
• Cache Breakdown
• Cache Avalanche

Why talk about cache stability in the first place? You can recall when we introduce caching? Usually it is when the DB is under pressure or even frequently hit and hung that we introduce caching, so we first introduced the caching system to solve the stability problem.

Cache Penetration

The reason for the existence of cache penetration is the request for non-existent data, from the figure we can see that request 1 for the same data will go to the cache first, but because the data does not exist, so there is certainly no cache, then it will fall to the DB, request 2 and request 3 for the same data will also fall to the DB through the cache, so when a large number of requests for non-existent data DB pressure will be particularly large, especially It is possible that malicious requests will break down (people with bad intentions will find a data does not exist and then launch a lot of requests for this non-existent data).

The solution of go-zero is that we also store a placeholder in the cache for non-existent data requests for a short time (say one minute), so that the number of DB requests for the same non-existent data will be decoupled from the actual number of requests, and of course, on the business side, we can also remove the placeholder when adding new data to ensure that the new data can be queried immediately.

#cache #web-development #golang #go