Redis Sentinel Cluster with Ansible

This Ansible playbook sets up a three-node Redis Sentinel cluster on Ubuntu servers for high availability using the official Redis APT repository.

Architecture

• 3 Redis instances (1 master, 2 slaves)
• 3 Sentinel instances (one on each server)
• Automatic failover capability
• Uses official Redis APT packages

Prerequisites

• 3 Ubuntu servers (18.04 or later)
• SSH access to all servers
• Python 3 installed on target servers
• Ansible installed on control machine

Quick Start

1. Update the inventory file with your server IPs:

   cp inventory/hosts.example inventory/hosts
   # Edit inventory/hosts with your server details

2. Configure variables in group_vars/all.yml if needed

3. (Optional) Check available Redis versions:

   ansible-playbook -i inventory/hosts check-redis-versions.yml

4. Run the playbook:

   ansible-playbook -i inventory/hosts site.yml

Configuration

• Redis configuration: templates/redis.conf.j2
• Sentinel configuration: templates/sentinel.conf.j2
• Variables: group_vars/all.yml

Redis Version

By default, the latest available Redis version will be installed. To install a specific version:

1. Check available versions: ansible-playbook -i inventory/hosts check-redis-versions.yml
2. Set redis_version in group_vars/all.yml (e.g., redis_version: "6:7.4.2-1rl1~jammy1")

Installation Method

This playbook follows the official Redis documentation for APT installation:

• Adds the official Redis APT repository
• Installs Redis using APT package manager
• Supports version specification
• Uses systemd for service management

Testing

After deployment, you can test the cluster:

# Connect to Redis master
redis-cli -h <master-ip> -p 6379

# Check sentinel status
redis-cli -h <any-server-ip> -p 26379 sentinel masters

Troubleshooting

Permission Issues

If you encounter permission errors (e.g., for /etc/redis/sentinel.conf):

1. Run the debug playbook to check permissions:

   ansible-playbook -i inventory/hosts debug-permissions.yml

2. Check if the redis user exists and has proper permissions:

   ansible -i inventory/hosts redis_cluster -m command -a "id redis" --become

3. Verify directory permissions:

   ansible -i inventory/hosts redis_cluster -m command -a "ls -la /etc/redis" --become

Package Issues

If redis-sentinel package is not found:

1. Check available packages:

   ansible-playbook -i inventory/hosts check-sentinel-package.yml

2. Verify Redis repository is properly added:

   ansible -i inventory/hosts redis_cluster -m command -a "apt-cache policy redis" --become

Alternative Configuration Directory

If /etc/redis cannot be created, the playbook will automatically fall back to /opt/redis/conf.

Security Notes

• Consider setting up firewall rules
• Use Redis AUTH for production
• Configure SSL/TLS if needed