How to use redis to solve concurrency problems

summary

redis As a cache component , Generally speaking, it is used to cache the data of our program . So there may be two aspects of concurrency , One is redis Data concurrency in cache , One is the data concurrency of business programs .

redis Cache data concurrency problem

 scene 1：
   What we do is a blog system , You need to collect and count the likes of each article , It is a concurrent behavior for multiple users to like at the same time ,
   Generally speaking, there is a data concurrency problem at this time . The initial number of likes for the article is 0, At this time, Zhang San and Li Si are writing an article at the same time 
   Like it , The initial values obtained are 0, All the likes are +1, Update back at this time , The number of likes is 1 了 .
  
   Solution ： Use it directly redis Of incr Command statistics is enough . because redis Is a single thread processing instructions （ lock ）, And then this incr Instruction is 
           Single instruction read / write is an atomic operation （ visibility , Atomicity ）, Therefore, there is no data concurrency coverage problem .
           
 scene 2：
   Suppose our blog system has a recommendation function , When users like , You also need to tag a user who likes a certain type of blog , next time 
   You can recommend similar articles to users . This time involves two operations , Number of likes +