Cache Service (Redis)

LocalCloud includes Redis configured as a caching layer to dramatically improve application performance by storing frequently accessed data in memory.

What is Redis Cache?

Redis is an in-memory data structure store used as a cache in LocalCloud. It provides:

Sub-millisecond latency - Extremely fast data access
Multiple data types - Strings, hashes, lists, sets, sorted sets
Atomic operations - Thread-safe operations
TTL support - Automatic expiration of cached data

Connection Details

When the cache service is running:

Host: localhost
Port: 6379
Database: 0 (default)
Password: None (local development)

Connection String

redis://localhost:6379

Getting Started

Start Cache Service

# Start all services (including cache)
lc start

# Start only cache service
lc start cache

# Check cache status
lc status cache

Connect to Redis

# Connect via redis-cli (if installed)
redis-cli -h localhost -p 6379

# Or connect through LocalCloud
lc redis connect

Common Cache Patterns

Basic Key-Value Caching

# Set a cached value with TTL (Time To Live)
SET user:123 "{"name":"John","email":"john@example.com"}" EX 3600

# Get cached value
GET user:123

# Delete cached value
DEL user:123

# Check if key exists
EXISTS user:123

Session Storage

# Store user session (expires in 24 hours)
SETEX session:abc123 86400 "{"userId":123,"role":"user"}"

# Get session data
GET session:abc123

# Update session expiry
EXPIRE session:abc123 86400

Counters and Rate Limiting

# Increment counter
INCR page_views:home
INCRBY downloads:app 5

# Rate limiting (allow 100 requests per hour)
SET rate_limit:user:123 1 EX 3600
INCR rate_limit:user:123

Lists for Recent Items

# Add recent activity (keep last 10 items)
LPUSH recent_posts:user:123 "post_456"
LTRIM recent_posts:user:123 0 9

# Get recent items
LRANGE recent_posts:user:123 0 -1

Application Integration

Python with redis-py

import redis
import json
from datetime import timedelta

# Connect to Redis
r = redis.Redis(host='localhost', port=6379, db=0)

# Cache user data
def get_user(user_id):
    cache_key = f"user:{user_id}"
    
    # Try to get from cache first
    cached_user = r.get(cache_key)
    if cached_user:
        return json.loads(cached_user)
    
    # If not in cache, get from database
    user = fetch_user_from_database(user_id)
    
    # Cache for 1 hour
    r.setex(cache_key, timedelta(hours=1), json.dumps(user))
    
    return user

# Session management
def set_session(session_id, user_data):
    r.setex(f"session:{session_id}", timedelta(days=1), json.dumps(user_data))

def get_session(session_id):
    session_data = r.get(f"session:{session_id}")
    return json.loads(session_data) if session_data else None

Node.js with ioredis

const Redis = require('ioredis');

const redis = new Redis({
    host: 'localhost',
    port: 6379,
    retryDelayOnFailover: 100
});

// Cache API responses
async function cacheApiResponse(endpoint, data, ttl = 3600) {
    await redis.setex(`api:${endpoint}`, ttl, JSON.stringify(data));
}

async function getCachedResponse(endpoint) {
    const cached = await redis.get(`api:${endpoint}`);
    return cached ? JSON.parse(cached) : null;
}

// Rate limiting middleware
async function rateLimitMiddleware(userId, limit = 100, window = 3600) {
    const key = `rate_limit:${userId}`;
    const current = await redis.incr(key);
    
    if (current === 1) {
        await redis.expire(key, window);
    }
    
    return current <= limit;
}

Go with go-redis

package main

import (
    "context"
    "encoding/json"
    "time"
    "github.com/go-redis/redis/v8"
)

var ctx = context.Background()

func main() {
    rdb := redis.NewClient(&redis.Options{
        Addr: "localhost:6379",
        DB:   0,
    })

    // Cache struct data
    type User struct {
        ID   int    `json:"id"`
        Name string `json:"name"`
    }

    user := User{ID: 123, Name: "John"}
    
    // Serialize and cache
    userData, _ := json.Marshal(user)
    rdb.Set(ctx, "user:123", userData, time.Hour)

    // Retrieve and deserialize
    val, err := rdb.Get(ctx, "user:123").Result()
    if err == nil {
        var cachedUser User
        json.Unmarshal([]byte(val), &cachedUser)
    }
}

Cache Strategies

Cache-Aside (Lazy Loading)

def get_product(product_id):
    # 1. Check cache first
    cache_key = f"product:{product_id}"
    product = r.get(cache_key)
    
    if product:
        return json.loads(product)
    
    # 2. Cache miss - get from database
    product = db.get_product(product_id)
    
    # 3. Store in cache for next time
    if product:
        r.setex(cache_key, 3600, json.dumps(product))
    
    return product

Write-Through Cache

def update_product(product_id, product_data):
    # 1. Update database
    db.update_product(product_id, product_data)
    
    # 2. Update cache immediately
    cache_key = f"product:{product_id}"
    r.setex(cache_key, 3600, json.dumps(product_data))

Cache Invalidation

def invalidate_user_cache(user_id):
    # Remove specific user data
    r.delete(f"user:{user_id}")
    
    # Remove related cached data
    r.delete(f"user_posts:{user_id}")
    r.delete(f"user_profile:{user_id}")

def invalidate_pattern(pattern):
    # Remove all keys matching pattern
    keys = r.keys(pattern)
    if keys:
        r.delete(*keys)

Monitoring and Debugging

Check Cache Stats

# Get Redis info
INFO memory
INFO stats

# Monitor commands in real-time
MONITOR

# Get slow queries
SLOWLOG GET 10

Using LocalCloud CLI

# View cache logs
lc logs cache

# Get cache information
lc redis info

# Connect to Redis CLI
lc redis connect

Configuration

Configure cache in .localcloud/config.yaml:

services:
  cache:
    port: 6379
    memory_limit: 256MB
    redis:
      maxmemory_policy: "allkeys-lru"  # Eviction policy
      save: "900 1 300 10 60 10000"    # Persistence settings
      databases: 16                     # Number of databases

Performance Tips

Memory Optimization

# Use appropriate data types
# Hash for objects with many fields
HSET user:123 name "John" email "john@example.com" age 30

# Use compression for large values
# Consider msgpack or similar

# Set appropriate TTLs
SET large_data:123 "..." EX 1800  # 30 minutes

Connection Pooling

import redis

# Use connection pooling
pool = redis.ConnectionPool(
    host='localhost', 
    port=6379, 
    max_connections=10
)
r = redis.Redis(connection_pool=pool)

Common Use Cases

Web Application Caching

Page fragments - Cache rendered HTML components
API responses - Cache database query results
User sessions - Store authentication state
Shopping carts - Temporary user data

AI Application Caching

Model outputs - Cache LLM responses for repeated queries
Embeddings - Cache vector embeddings for documents
Feature vectors - Cache computed features
Rate limiting - Control API usage per user

Real-time Applications

Leaderboards - Sorted sets for rankings
Chat messages - Lists for message history
Notifications - Queues for real-time updates
Analytics - Counters for metrics

Troubleshooting

Memory Issues

# Check memory usage
lc redis info memory

# Clear all cache data
lc redis flushall

# Check cache hit ratio
lc redis info stats | grep hit_rate

Connection Issues

# Check if Redis is running
lc status cache

# Restart cache service
lc restart cache

# View cache logs
lc logs cache

Queue Service - Redis-based job queues
CLI Redis Commands - Command-line Redis operations
Database - Primary data storage

Best Practices

Set appropriate TTLs - Prevent cache from growing indefinitely
Use consistent naming - Organize keys with prefixes
Monitor memory usage - Avoid running out of memory
Handle cache misses gracefully - Always have fallback to database
Consider cache warming - Pre-load frequently accessed data
Use transactions when needed - MULTI/EXEC for atomic operations

Getting Started

Core Concepts

Using Services

CLI Commands

Troubleshooting

​Cache Service (Redis)

​What is Redis Cache?

​Connection Details

​Connection String

​Getting Started

​Start Cache Service

​Connect to Redis

​Common Cache Patterns

​Basic Key-Value Caching

​Session Storage

​Counters and Rate Limiting

​Lists for Recent Items

​Application Integration

​Python with redis-py

​Node.js with ioredis

​Go with go-redis

​Cache Strategies

​Cache-Aside (Lazy Loading)

​Write-Through Cache

​Cache Invalidation

​Monitoring and Debugging

​Check Cache Stats

​Using LocalCloud CLI

​Configuration

​Performance Tips

​Memory Optimization

​Connection Pooling

​Common Use Cases

​Web Application Caching

​AI Application Caching

​Real-time Applications

​Troubleshooting

​Memory Issues

​Connection Issues

​Related Documentation

​Best Practices

Cache Service (Redis)

What is Redis Cache?

Connection Details

Connection String

Getting Started

Start Cache Service

Connect to Redis

Common Cache Patterns

Basic Key-Value Caching

Session Storage

Counters and Rate Limiting

Lists for Recent Items

Application Integration

Python with redis-py

Node.js with ioredis

Go with go-redis

Cache Strategies

Cache-Aside (Lazy Loading)

Write-Through Cache

Cache Invalidation

Monitoring and Debugging

Check Cache Stats

Using LocalCloud CLI

Configuration

Performance Tips

Memory Optimization

Connection Pooling

Common Use Cases

Web Application Caching

AI Application Caching

Real-time Applications

Troubleshooting

Memory Issues

Connection Issues

Related Documentation

Best Practices