How to Build a Redis High‑Availability Cluster with Sentinel and VIP

Architecture Overview

Deploy three Redis instances (one master, two slaves) on separate hosts and use Redis Sentinel for automatic failover. Optionally use a floating virtual IP (VIP) that always points to the current master.

Installation

wget http://download.redis.io/releases/redis-3.2.8.tar.gz
 tar zxvf redis-3.2.8.tar.gz
 cd redis-3.2.8
 make
 cd src
 sudo cp redis-cli redis-server redis-sentinel /usr/sbin/
 sudo cp redis.conf sentinel.conf /etc/

Master Configuration (redis.conf)

port 8000
daemonize yes
bind 0.0.0.0
pidfile /var/run/redis-8000.pid
logfile /var/log/redis/redis-8000.log

Slave Configuration (redis.conf)

port 8000
daemonize yes
bind 0.0.0.0
pidfile /var/run/redis-8000.pid
logfile /var/log/redis/redis-8000.log
slaveof 192.168.56.101 8000

Start Redis Servers

sudo redis-server /etc/redis.conf

Run the above command on each host, using the master configuration on the designated master and the slave configuration on the other two hosts.

Verify Replication

redis-cli -h 192.168.56.101 -p 8000 info replication

If no slave information appears, open firewall ports 8000 and 6800:

sudo vim /etc/sysconfig/iptables   # add rules for 8000 and 6800
sudo service iptables restart

Sentinel Configuration (sentinel.conf)

daemonize yes
port 6800
logfile /var/log/redis/sentinel.log
pidfile /var/run/sentinel.pid
sentinel monitor master8000 192.168.56.101 8000 2
sentinel down-after-milliseconds master8000 5000
sentinel failover-timeout master8000 15000
# Optional VIP migration script
sentinel client-reconfig-script master8000 /opt/notify_master6800.sh

Start Sentinel

redis-sentinel /etc/sentinel.conf

Failover Test

Shut down the master: redis-cli -h 192.168.56.101 -p 8000 shutdown Query any Sentinel for the new master address: SENTINEL get-master-addr-by-name <master-name> Sentinel will return the IP and port of the promoted slave (e.g., 192.168.56.102).

Client Integration

Before each Redis operation, a client can request the current master address using the Sentinel command above. A PHP example is available at https://github.com/huyanping/redis-sentinel (plain text reference).

VIP Migration (optional)

Assign a floating IP (e.g., 192.168.56.250) to the master. When Sentinel promotes a new master, it runs a script to move the VIP.

notify_master6800.sh

#!/bin/bash
MASTER_IP=$6               # new master IP passed by Sentinel
LOCAL_IP='192.168.56.101'  # change per host
VIP='192.168.56.250'
NETMASK='24'
INTERFACE='eth1'

if [ "$MASTER_IP" = "$LOCAL_IP" ]; then
    /sbin/ip addr add ${VIP}/${NETMASK} dev ${INTERFACE}
    /sbin/arping -q -c 3 -A ${VIP} -I ${INTERFACE}
else
    /sbin/ip addr del ${VIP}/${NETMASK} dev ${INTERFACE}
fi
exit 0

Manually bind the VIP to the current master (example for 192.168.56.102):

/sbin/ip addr add 192.168.56.250/24 dev eth1
/sbin/arping -q -c 3 -A 192.168.56.250 -I eth1

Summary

This configuration provides high availability for a single Redis instance using master‑slave replication, Sentinel automatic failover, and optional VIP migration. For larger workloads, consider Redis Cluster or other clustering solutions.