How to Set Up Redis Caching

This guide walks you through configuring ElixirCache with Redis as the backend.

Prerequisites

Before setting up Redis with ElixirCache, make sure you have:

1. Redis server installed and running
2. ElixirCache properly installed in your project

Basic Redis Configuration

Step 1: Define Your Redis Cache Module

Create a module that uses the Cache functionality with the Redis adapter:

defmodule MyApp.RedisCache do
  use Cache,
    adapter: Cache.Redis,
    name: :my_app_redis,
    opts: [
      uri: "redis://localhost:6379",
      size: 10,
      max_overflow: 5
    ]
end

Step 2: Add to Your Supervision Tree

Make sure to add your Redis cache to your application's supervision tree:

def start(_type, _args) do
  children = [
    # ... other children
    MyApp.RedisCache
  ]

  opts = [strategy: :one_for_one, name: MyApp.Supervisor]
  Supervisor.start_link(children, opts)
end

Redis Configuration Options

The Redis adapter accepts the following options:

Authentication, database selection, and SSL are configured via the URI string:

defmodule MyApp.RedisCache do
  use Cache,
    adapter: Cache.Redis,
    name: :my_app_redis,
    opts: [
      uri: "redis://:my_password@redis.example.com:6379/2",
      size: 10,
      max_overflow: 5
    ]
end

Environment-Based Configuration

For better maintainability, consider using environment variables or configuration files:

defmodule MyApp.RedisCache do
  use Cache,
    adapter: Cache.Redis,
    name: :my_app_redis,
    opts: [
      uri: System.get_env("REDIS_URL", "redis://localhost:6379"),
      size: String.to_integer(System.get_env("REDIS_POOL_SIZE", "10")),
      max_overflow: 5
    ]
end

Working with Redis-Specific Features

The Redis adapter provides some Redis-specific functionality beyond the standard cache interface:

Hash Operations

# Set hash field
MyApp.RedisCache.hash_set("user:1", "name", "John")
MyApp.RedisCache.hash_set("user:1", "email", "john@example.com")

# Get hash field
{:ok, name} = MyApp.RedisCache.hash_get("user:1", "name")

# Get all hash fields
{:ok, user_data} = MyApp.RedisCache.hash_get_all("user:1")

# Delete hash field
MyApp.RedisCache.hash_delete("user:1", "email")

JSON Operations

# Store JSON
json_data = %{users: [%{id: 1, name: "Alice"}, %{id: 2, name: "Bob"}]}
MyApp.RedisCache.json_set("app:data", ".", json_data)

# Get JSON 
{:ok, data} = MyApp.RedisCache.json_get("app:data", ".")

# Get nested JSON path
{:ok, users} = MyApp.RedisCache.json_get("app:data", ".users")

# Update specific path
MyApp.RedisCache.json_set("app:data", ".users[0].name", "Alicia")

Troubleshooting Redis Connection

If you're having issues connecting to Redis:

1. Verify Redis is running: redis-cli ping should return PONG
2. Check connection settings: Ensure host, port, and password are correct
3. Network issues: Ensure your application can reach the Redis server (firewalls, network rules)
4. Authentication: Confirm your Redis password is correct if authentication is enabled
5. Connection pool: Monitor your connection pool usage to ensure you haven't exhausted connections

Redis in Production

For production environments, consider:

1. Use a dedicated Redis instance or managed Redis service
2. Enable persistence in Redis if you need data to survive restarts
3. Configure appropriate timeouts based on your application needs
4. Monitor Redis performance using tools like Prometheus and Grafana
5. Set up proper SSL if connecting to Redis over untrusted networks