What to do if Redis requires more memory than available memory

We know that Redis sets the maxmemory parameter of the configuration file to control its maximum available memory size (bytes).

What if the required memory exceeds MaxMemory ?

This time the maxmemory-policy in the configuration file appeared.

Its default value is noeviction.

Below I will list the elimination rules that are available when the Redis key is removed when there is not enough free memory.

Rule name	Rule description
Volatile-lru	Remove a key using the LRU algorithm (only for keys that have a time-to-live setting)
Allkeys-lru	Remove a key using the LRU algorithm
Volatile-random	Randomly delete a key (only for keys that have a time-to-live setting)
Allkeys-random	Randomly delete a key
Volatile-ttl	Delete one of the most recent keys to survival time
Noeviction	Do not delete keys, only return errors

The LRU algorithm , least recently used, is the least recently used algorithm . This means that the least recently used key is deleted by default.

But be sure to pay attention to a little ! Instead of accurately deleting the least recently used keys in all keys, Redis randomly extracts 3 keys , removing the least recently used keys from the three keys.

Then 3 this number can also be set, the corresponding location is the maxmeory-samplesin the configuration file.

How does Redis require more memory than is available?