Why Does an OOM Error Occur During a Redis Connection?

Symptom

"Error in execution; nested exception is io.lettuce.core.RedisCommandExecutionException: OOM command not allowed when used memory > 'maxmemory'" is returned during a Redis connection.

Fault Locating

An out-of-memory (OOM) error indicates that the maximum memory is exceeded. In the error information, the maxmemory parameter indicates the maximum memory configured on the Redis server.

If the memory usage of the Redis instance is less than 100%, the memory of the node where data is written may have reached the maximum limit. Connect to each node in the cluster by running redis-cli -h <redis_ip> -p 6379 -a <redis_password> -c --bigkeys. When connecting to a replica node, run the READONLY command before running the bigkeys command.