Cache penetration and avalanche processing technology in PHP

1. Advantages and Common Problems of Caching

With the growth of data volume and concurrency of modern websites, caching technology has become an important means of website performance optimization. Caching technology can greatly reduce database access and speed up data query. In PHP, caching tools such as Memcached and Redis are mainly used to implement caching functions.

The advantage of caching is that it can improve the response speed of the system, reduce access to back-end data sources, and reduce the load on the server. However, cache will also face some problems, the biggest problems are cache penetration and cache avalanche.

2. The concept and solution of cache penetration

Cache penetration means that when looking for data in the cache, the back-end data source is continuously queried because the data does not exist, resulting in a decrease in system performance. . The main reason is that attackers maliciously query non-existent data, making it impossible to hit the data in the cache, thus continuously accessing back-end data sources.

For cache penetration, the following solutions are currently used:

1. Cache empty data values ​​in the cache, that is, the cache for non-existent data is not empty, so that you can After discovering that the data does not exist, it directly returns the null value in the cache without continuing to issue query requests to the back-end data source.

2. Requests for querying non-existent data can be filtered at the cache layer, such as using data structures such as Bloom filters to store the possible data through hash calculation and detect whether the queried data is exists in the data, or returns immediately if it does not exist, avoiding continuous access to the backend data source.

3. The concept and solution of cache avalanche

Cache avalanche means that the data stored in the cache becomes invalid at the same time, resulting in a large number of requests accessing the back-end data source at the same time, thus causing a huge impact on the back-end. The data source causes certain load pressure and even paralyzes the entire system. The main reason is that all the data in the cache expires at the same time, making it unable to serve it efficiently.

Currently, the following solutions are mainly used to deal with cache avalanche:

1. Randomize the cache expiration time, that is, add a random time to the expiration time of the cached data, so that the cache The data will not be invalidated at the same time, thereby increasing the effectiveness and stability of the cache.

2. Use a multi-level cache architecture and add another cache layer on top of the cache layer to prevent cache penetration and cache avalanche. At the same time, cache layers can also back up each other to improve data reliability.

3. Preloading, by preloading data during low business peak periods, hotspot data is loaded into the cache in advance to reduce cache pressure during peak periods and improve system stability.

4. Conclusion

In the process of website performance optimization, caching technology is a very important part. However, the two problems of cache penetration and cache avalanche also bring great challenges to the website, and certain measures need to be taken to solve them. Through reasonable caching strategies, the stability and response speed of the website can be improved, thereby improving the user experience.

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