Replication in Redis is a powerful feature that allows you to create copies of your Redis database across multiple servers. This ensures high availability, load balancing, and data redundancy. In this section, we will cover the basics of replication, how to set it up, and some common use cases.

Replication in Redis involves copying data from one Redis server (the master) to one or more Redis servers (the replicas). The replicas maintain a copy of the master’s data and can serve read requests, which helps in distributing the load and providing high availability.

• Master: The primary Redis server that handles all write operations.
• Replica: A secondary Redis server that maintains a copy of the master’s data and can handle read operations.
• Replication Link: The connection between the master and its replicas.

1. Install Redis: Ensure Redis is installed on both the master and replica servers. Refer to the "Installing Redis" section if needed.

2. Configure the Master:

   • No special configuration is needed for the master. Just ensure it is running and accessible.

3. Configure the Replica:

   • Edit the redis.conf file on the replica server.
   • Add the following line to specify the master server:

     replicaof <master-ip> <master-port>
     

     For example:

     replicaof 192.168.1.100 6379
     

4. Start the Replica:

   • Start the Redis server on the replica machine:

     redis-server /path/to/redis.conf
     

5. Verify Replication:

   • Connect to the replica using the Redis CLI:

     redis-cli
     

   • Run the INFO replication command to check the replication status:

     INFO replication
     

   • You should see output indicating that the server is a replica and connected to the master.

Master Configuration (redis.conf):

Replica Configuration (redis.conf):

1. Start the master Redis server:

   redis-server /path/to/master/redis.conf
   

2. Add some data to the master:

   redis-cli
   set key1 "value1"
   

1. Start the replica Redis server:

   redis-server /path/to/replica/redis.conf
   

2. Verify that the data is replicated:

   redis-cli
   get key1
   

   • The output should be:

     "value1"
     

• High Availability: Ensures that data is available even if the master server fails.
• Load Balancing: Distributes read requests across multiple replicas to reduce the load on the master.
• Data Redundancy: Provides multiple copies of data to prevent data loss.

1. Objective: Set up a master and replica Redis server and verify that data is replicated.
2. Steps:
   • Install Redis on two servers (or two instances on the same machine).
   • Configure one server as the master and the other as the replica.
   • Add data to the master and verify that it appears on the replica.

1. Master Configuration:

   • No special configuration needed.

2. Replica Configuration:

   • Add replicaof <master-ip> <master-port> to the redis.conf file.

3. Verification:

   • Add data to the master using redis-cli set key1 "value1".
   • Check the replica using redis-cli get key1.

In this section, we covered the basics of Redis replication, including how to set up a master and replica server, and how to verify that replication is working. Replication is a crucial feature for ensuring high availability, load balancing, and data redundancy in Redis deployments. In the next section, we will explore Redis Sentinel, which provides automated failover and monitoring for Redis replication setups.