how-to-change-redis-eviction-policy.md

myst	html_meta description title Changing the Redis eviction policy on Hypernode with hypernode-systemctl. Learn which policies are available and how to verify the active Redis maxmemory-policy. Changing the Redis eviction policy on Hypernode

Changing the Redis eviction policy

You can change the Redis maxmemory-policy with hypernode-systemctl settings redis_eviction_policy. This policy determines which keys Redis can evict when memory is full.

Available policies

The following values are supported for redis_eviction_policy:

• noeviction
• allkeys-lru
• allkeys-lfu
• allkeys-random
• volatile-lru
• volatile-lfu
• volatile-ttl
• volatile-random

By default, Redis on Hypernode uses the `volatile-lru` eviction policy.

Check the current policy

To view the current Redis eviction policy:

hypernode-systemctl settings redis_eviction_policy

Change the policy

Use the following command to change the Redis eviction policy:

hypernode-systemctl settings redis_eviction_policy <policy>

For example:

hypernode-systemctl settings redis_eviction_policy allkeys-lru

Policy explanation

noeviction

Redis will not evict any keys when memory is full. New write operations that require memory will fail.

allkeys-lru

Redis can evict any key and removes the least recently used keys first.

allkeys-lfu

Redis can evict any key and removes the least frequently used keys first.

allkeys-random

Redis can evict any key and removes keys at random.

volatile-lru

Redis only evicts keys with an expiration time and removes the least recently used keys first.

This is the default policy on Hypernode.

volatile-lfu

Redis only evicts keys with an expiration time and removes the least frequently used keys first.

volatile-ttl

Redis only evicts keys with an expiration time and prefers keys that will expire soonest.

volatile-random

Redis only evicts keys with an expiration time and removes those keys at random.

Important considerations

• Eviction only takes place when Redis reaches its memory limit.
• Policies starting with allkeys- can evict any key, including keys without a TTL.
• Even with an allkeys- policy, Redis can still run into memory pressure if keys cannot be evicted fast enough to keep up with writes.
• Setting a TTL on cache keys is still recommended, even when using an allkeys- policy.
• Policies starting with volatile- only apply to keys with a TTL.
• If not enough keys have a TTL, Redis may not be able to evict enough data with a volatile- policy, and write operations may fail.
• Changing the policy does not remove existing keys immediately.