redis cache cleaning mechanism

Redis cache cleaning mechanism adopts elimination strategy, memory overflow strategy and manual elimination to free up space to accommodate new data. Commonly used elimination strategies include LRU, LFU, and FIFO; memory overflow strategies include volatile-lru, volatile-lfu, and allkeys-lru. Additionally, Redis supports lazy deletion and manual eviction using the DEL and UNLINK commands to help maintain cache validity.

Redis cache cleaning mechanism

Redis cache cleaning mechanism answers the following questions:

• When the data stored in the Redis cache exceeds its capacity limit, how will Redis free up space to accommodate new data?

Detailed explanation of cache cleaning mechanism:

Redis provides a variety of cache cleaning mechanisms to ensure that space can be released to store new data when the cache capacity is insufficient. These mechanisms include:

• Elimination strategy: Redis selects cache items to be deleted when space needs to be made according to a specific eviction strategy. The most common strategies are:

  • LRU (Least Recently Used): Delete the cache item that has been used the longest recently.
  • LFU (least recently used): Delete the least frequently used cache item.
  • FIFO (First In, First Out): Delete the first cache entry added to the cache.

• Memory overflow policy: When the memory used by the Redis process exceeds its configured limit, Redis will trigger the memory overflow policy. This policy allows Redis to release idle memory to avoid the process being terminated by the operating system. The most common strategies are:

  • volatile-lru: Similar to the LRU strategy, but only deletes cache entries with the volatile flag.
  • volatile-lfu: Similar to the LFU policy, but only deletes cache entries with the volatile flag.
  • allkeys-lru: Delete all cache entries regardless of whether the volatile flag is present, until sufficient memory is freed.
• Manual elimination: Redis also provides a command to manually trigger cache elimination DEL and UNLINK. These commands allow developers to delete specific cache items as needed.
• Lazy deletion: Redis will lazily delete certain types of cache items. For example, when the key to be retrieved has an Expiration Time (TTL), Redis will not delete it immediately, but will delete it on the next access.

Choose the appropriate cleaning strategy:

Choosing the best cache cleaning strategy depends on the specific needs of your application. For most applications, the LRU policy is usually a solid choice because it balances the freshness of cache items with the need to free up space. However, for high-traffic environments or applications where data changes frequently, an LFU or FIFO strategy may be more appropriate.

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