How to avoid cache penetration in Java caching technology

With the development of Internet technology, caching technology has become an important means to improve website performance. Java caching technology is one of the important technologies. In actual use, we often encounter a problem, which is the cache penetration problem. The cache penetration problem means that the cached data does not exist, but requests are frequent, resulting in a large number of requests directly hitting the database, causing increased pressure on the database, and in severe cases, causing a system crash. This article will introduce how to avoid cache penetration problems in Java caching technology.

1. What is cache penetration?

The cache penetration problem means that when querying data, it is found that the data is not in the cache, and each query is not in the cache, thus causing each request to fail. Hit the database. In this case, the database will be under greater request pressure, and the cache will not play its due role.

2. Reasons for cache penetration

1. The query parameter is illegal or does not exist: When the query parameter is illegal or does not exist, the request will not be cached, and each request needs to be Query in database.
2. Data expiration: Expired data will be removed, and each request needs to query the data from the database.
3. Frequent queries for non-existent data: When frequent queries for non-existent data, these requests will be directly hit to the database.

3. How to avoid cache penetration problems

1. Cache empty objects

When the query cache data does not exist, in order to avoid For frequent database requests, we can cache empty objects or data, so that the cache can be guaranteed to exist even if there is no data. However, empty objects also need to be expired, otherwise it will cause cache expiration problems.

2. Bloom filter

The Bloom filter is an efficient data structure that can be used to check whether an element exists in a set. It can be Provide effective solutions in time and space. Before querying data, we can first use a Bloom filter to verify whether the query parameters are legal. If it is not legal, the result will be returned directly without querying the cache or database; if it is legal, the result will be returned directly or the data will be queried from the database.

3. Parameter verification

Before querying the cached data, you can verify the query parameters. If the query parameters are illegal, the results will be returned directly without querying the cache and database.

4. Cache preheating

In the preheating stage, we can add frequently accessed data to the cache, which can greatly reduce the situation where data does not exist in the query cache. For data that is rarely accessed, we can do it without preheating or using manual preheating.

5. Current limiting measures

When the cache does not hit, we can perform current limiting processing to limit the frequency of requests to avoid a large number of requests directly hitting the database. Common current limiting schemes include: token bucket algorithm, leaky bucket algorithm, etc.

4. Summary

The cache penetration problem is something we will definitely encounter in the process of using Java cache technology. Understanding the causes and solutions of cache penetration can effectively alleviate the problem of database pressure to improve website performance. In actual development, the above technologies and measures should be used comprehensively to avoid cache penetration problems.

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