Question: Why should one use replication in Redis?

Answer

Replication in Redis allows a Redis server to function as an exact replica of another server. This feature serves several essential purposes:

1. Fault tolerance and high availability: Replication provides a failover solution when the master server crashes or becomes unavailable for some reason. The slave servers can take over and continue serving client requests without significant downtime.

2. Data redundancy: Having multiple copies of data across different servers ensures that data is not lost if a server goes down or fails.

3. Load balancing: Read operations can be distributed among master and slave servers, reducing the load on any single server and increasing overall system performance.

4. Data safety and backups: Slave servers can be used for regular backup processes, which minimizes the performance impact on the master server.

Here's an example of how to set up a replication:

# On the slave node, run this command to make it a replica of the master
redis-cli SLAVEOF master_host master_port

And here is how you can stop being a replica:

# On the slave node, run this command to stop being a replica
redis-cli SLAVEOF NO ONE

As a best practice, remember to monitor the state of your replicas to ensure they're fully synchronized with the master and operate as expected. You can do this using the INFO REPLICATION command in Redis.

# Run this command on either master or slave node to get information about replication
redis-cli INFO REPLICATION