What is redis cache penetration

Cache penetration means that data not stored in the cache directly accesses the database, which can be solved through bloom filters, null value caching, and circuit breaker mechanisms.

What is Redis cache penetration?

Redis cache penetration means that when the client requests data from the cache that is not stored in the cache, the cache server directly releases the request, causing the request to directly access the database.

How to understand cache penetration?

The function of cache is to temporarily store popular data to avoid frequent database queries and improve performance. However, when querying an unpopular data that does not exist in the cache, the cache directly releases the request, and the query penetrates to the database.

Causes leading to cache penetration:

• Malicious attack: The attacker deliberately queries non-existent data, resulting in a large number of invalid queries Penetrates into the database, causing performance bottlenecks.
• Complex business scenarios: The business logic is complex and there are many rare scenarios or edge cases, resulting in a large number of unpopular data queries.
• Improper cache configuration: The cache capacity is too small or the expiration policy is unreasonable, resulting in frequent invalidation of popular data.

Methods to solve cache penetration:

• Bloom filter: Use Bloom filter to pre-judge data Whether it exists in the cache, if so, it will be returned directly; if not, the request will be released.
• Null value cache: When no data is found in the cache, a null value is cached and the null value is returned to the client. This can effectively prevent subsequent invalid queries for the same data.
• Circuit breaker mechanism: When the cache penetration reaches a certain threshold, the circuit breaker mechanism is activated and all requests are released directly to the database to avoid further performance impact on the database.

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