Automatic failover in Redis - Mini Project: Build & Apply

Automatic Failover Setup in Redis

📖 Scenario: You are managing a Redis database for a small online store. To ensure the store stays online even if the main Redis server fails, you want to set up automatic failover using Redis Sentinel.

🎯 Goal: Set up a Redis Sentinel configuration that monitors a Redis master server and automatically promotes a replica to master if the master fails.

📋 What You'll Learn

Create a Redis master configuration with a specific name.

Create at least two Redis replica configurations.

Configure Redis Sentinel to monitor the master with a quorum of 2.

Set the failover timeout to 10000 milliseconds.

💡 Why This Matters

🌍 Real World

Automatic failover ensures that if the main Redis server crashes, a replica takes over immediately, keeping applications running smoothly without manual intervention.

💼 Career

Understanding Redis Sentinel and failover is important for roles like DevOps engineers, backend developers, and system administrators who maintain reliable and scalable database systems.

1

Create Redis master configuration

Create a Redis master configuration file named redis-master.conf with the following settings: set port 6379 and daemonize yes.

Redis

# Create redis-master.conf with port 6379 and daemonize yes
# Your code here

Need a hint?

Use port 6379 to set the port and daemonize yes to run Redis in the background.

2

Create Redis replica configurations

Create two Redis replica configuration files named redis-replica1.conf and redis-replica2.conf. Each should have port 6380 and port 6381 respectively, daemonize yes, and set replicaof 127.0.0.1 6379 to replicate the master.

Redis

port 6379
daemonize yes
# Create redis-replica1.conf with port 6380, daemonize yes, and replicaof 127.0.0.1 6379
# Your code here

Need a hint?

Each replica must have its own port and replicate the master at 127.0.0.1 port 6379.

3

Configure Redis Sentinel to monitor the master

Create a Redis Sentinel configuration file named sentinel.conf. Add the line sentinel monitor mymaster 127.0.0.1 6379 2 to monitor the master named mymaster at IP 127.0.0.1 port 6379 with a quorum of 2. Also add sentinel down-after-milliseconds mymaster 5000 and sentinel failover-timeout mymaster 10000.

Redis

# redis-master.conf
port 6379
daemonize yes

# redis-replica1.conf
port 6380
daemonize yes
replicaof 127.0.0.1 6379

# redis-replica2.conf
port 6381
daemonize yes
replicaof 127.0.0.1 6379

# Create sentinel.conf with monitor and failover settings
# Your code here

Need a hint?

The sentinel monitor line tells Sentinel what master to watch and the quorum needed. The other lines set timing for failover.

4

Complete Sentinel configuration with notification script

In sentinel.conf, add the line sentinel notification-script mymaster /usr/local/bin/notify.sh to specify a notification script that runs on failover events.

Redis

# redis-master.conf
port 6379
daemonize yes

# redis-replica1.conf
port 6380
daemonize yes
replicaof 127.0.0.1 6379

# redis-replica2.conf
port 6381
daemonize yes
replicaof 127.0.0.1 6379

# sentinel.conf
sentinel monitor mymaster 127.0.0.1 6379 2
sentinel down-after-milliseconds mymaster 5000
sentinel failover-timeout mymaster 10000
# Add notification script line below
# Your code here

Need a hint?

This line tells Sentinel to run a script when failover events happen, useful for alerts.