Cache avalanche and cache penetration solutions

Cache avalanche and cache penetration Cache avalanche : Simply put, cache invalidation , Originally, the cached data is directly accessed to the database , This causes great pressure on the database and memory , Serious problems may lead to database downtime 、 Server crash . Solution : 1. Use distributed locks or control the number of threads reading and writing to the database cache for columns , Ensure that there are threads to operate . Lack of This reduces the throughput of the system 2.redis Medium key The failure time shall be set as evenly as possible 3. Use mq To solve the cache avalanche effect . When a large number of requests for access redis No value in , Put the query parameters on the message queue , The consumer receives the message, queries the database, and returns the result to the generator in a synchronous manner . Message oriented middleware has the function of caching messages 4. Set L1 and L2 cache . If the L1 cache fails , Let access request L2 cache , It should be noted that the L2 cache expiration time is better than the L1 cache expiration time . 5. If it is one redis Server down , Can be built redis The main equipment High availability .

The upper level of the cache can also set the service degradation 、 Isolation 、 Fault tolerance 、 Fuse, etc. to prevent avalanche .—-springcloud Service governance framework , Service fault tolerance mechanism hystrix

Cache penetration : The process of caching : When users query data, they first query the cache , If the cache does not , Query the database , Put the result of the query into a cache , The next time you query, if there is data in the cache , It is directly returned to the client to reduce the pressure on the database . Cache penetration : The data queried by the user does not exist in the database , Therefore, there is no result of user query data in the cache . If someone maliciously attacks and uses this query data to query all the time , Causing database pressure to increase .

Solution :1. Cache an empty result of the query . This can simply and effectively avoid bypassing the cache and directly querying the database . 2. At the same time, you can also set a separate cache area to store null values , For the query key Pre check , And then release it to the normal cache processing logic

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