Redis Out of Memory Policy Rejection

Redis rejected the command because the 'maxmemory' limit was reached and the configured eviction policy ('maxmemory-policy') is set to 'noeviction' or the command would cause memory usage to exceed the limit.

Common Causes

The Redis instance has hit its configured 'maxmemory' limit.
The 'maxmemory-policy' is set to 'noeviction', which prevents keys from being evicted to make space.
An operation (like SET) requires more memory than is currently available under the limit.
Memory fragmentation is high, reducing usable memory within the limit.

How to Fix

1 Check Current Memory Configuration

Connect to Redis and check the current memory limit and usage to confirm the issue.

BASH

$ redis-cli INFO memory | grep -E "(used_memory_human|maxmemory_human|maxmemory_policy)"

2 Increase the Maxmemory Limit

Temporarily or permanently increase the memory limit in the Redis configuration file (redis.conf) or via runtime command.

BASH

 $ # In redis.conf
maxmemory 2gb

# Or at runtime (if supported by config)
redis-cli CONFIG SET maxmemory 2147483648

3 Change the Eviction Policy

Configure Redis to evict old keys when the limit is reached instead of rejecting commands. 'allkeys-lru' is a common choice.

BASH

 $ # In redis.conf
maxmemory-policy allkeys-lru

# Or at runtime
redis-cli CONFIG SET maxmemory-policy allkeys-lru

4 Free Memory by Flushing or Deleting Keys

Manually remove data to free up memory. Use FLUSHDB to clear the current database or DEL to remove specific keys.

BASH

 $ # Flush current database (DANGER: deletes all data)
redis-cli FLUSHDB

# Delete a specific key
redis-cli DEL my-large-key

5 Monitor and Optimize Memory Usage

Identify memory-hungry keys and optimize data structures (e.g., use hashes instead of many strings).

BASH

 $ # Find largest keys
redis-cli --bigkeys

# Get memory usage for a specific key pattern
redis-cli MEMORY USAGE myhashkey