Cache penetration refers to a query data does not exist, the buffer layer and the storage layer will not be hit, but for fault-tolerant considerations, finding out if the data storage layer from the buffer layer are written. Cache penetration will lead to the absence of data each request should go to the storage layer to query, cache protection loses its meaning back-end storage.
Cache penetration problem may cause back-end storage load increase, since many do not have the back-end storage of high concurrency, and may even cause back-end storage dang out. Respectively, the total number of statistics can often be called in the program, the number of hits caching layer, storage layer hits, if you find a lot of storage space hit the floor, probably appeared cache penetrating questions.
There are basically caused by the cache penetration of two.
First, the business of their own code or data problems,
Second, some malicious attacks, causing a large number of reptiles and other hits empty
