Redis Fundamentals in Practice — Caching, Sessions, and Message Queues

# Ubuntu
apt install redis-server

#
redis-cli ping  # PONG

redis-cli

# String
SET user:1:name "Alice"
GET user:1:name
INCR counter
INCRBY counter 10

# TTL (expiry)
SET session:abc "token" EX 3600 # 3600 after
TTL session:abc # when
PERSIST session:abc # TTL

# ( SCAN )
SCAN 0 MATCH user:* COUNT 100

HSET user:1 name "Alice" email "alice@example.com" age 30
HGET user:1 name
HGETALL user:1
HDEL user:1 age
HEXISTS user:1 email # 1 / 0

# FIFO
RPUSH tasks "job1" "job2" "job3"
LPOP tasks # "job1"
LLEN tasks #

#
BLPOP tasks 30 # 30

# Set
SADD tags "redis" "nosql" "cache"
SMEMBERS tags
SISMEMBER tags "redis"  # 1

# Sorted Set
ZADD leaderboard 1500 "alice"
ZADD leaderboard 2300 "bob"
ZRANGE leaderboard 0 -1 WITHSCORES #
ZREVRANGE leaderboard 0 2             # Top 3
ZINCRBY leaderboard 100 "alice" #

import redis, json

r = redis.Redis(host='localhost', port=6379)

def get_user(user_id):
    cache_key = f"user:{user_id}"
    cached = r.get(cache_key)

    if cached:
        return json.loads(cached)

    user = db.query(f"SELECT * FROM users WHERE id = {user_id}")
    r.setex(cache_key, 3600, json.dumps(user))
    return user

# 
redis-cli info memory
redis-cli info stats

# 
redis-cli --bigkeys

# 
redis-cli slowlog get 10