Question: What is the Redis replication buffer limit and how can it be adjusted?

Answer

Redis replication involves copying data from a master instance to one or more replica instances. This is done through a buffer, which stores the commands that modify the dataset. The size of this buffer is critical for performance and the successful operation of replication.

The client-output-buffer-limit directive in the Redis configuration file (redis.conf) is used to control this buffer limit. It allows you to specify different limits for normal clients, replicas, and pub/sub channels. Here's an example:

client-output-buffer-limit replica 256mb 64mb 60

In this line, 256mb is the hard limit, 64mb is the soft limit, and 60 is the time limit. When the hard limit is reached, the client is disconnected immediately. The soft limit works together with the time limit - if the output buffer reaches the soft limit and stays there for the specified time limit (in seconds), the client will also be disconnected.

To change the replication buffer limit, you can edit these values in the redis.conf file and then restart the Redis server for the changes to take effect.

Please note that setting the limit too low might cause frequent disconnections, while setting it too high might lead to excessive memory consumption. It's important to balance these considerations based on your specific use case and server capacity.