Redis在即时通讯系统中的作用及应用

def get_user_info(user_id):
    # 先尝试从缓存中获取用户信息
    user_info = redis.get("user_info_" + str(user_id))
    if user_info:
        return JSON.loads(user_info)
        
    # 如果缓存中没有，从数据库中获取，并存入缓存
    user = User.objects.get(id=user_id)
    user_info = {
        "id": user.id,
        "name": user.name,
        "age": user.age
    }
    redis.set("user_info_" + str(user_id), json.dumps(user_info))
    
    return user_info

def get_message_history(user_id):
    # 先尝试从缓存中获取消息记录
    message_history = redis.lrange("message_history_" + str(user_id), 0, -1)
    if message_history:
        return [json.loads(item) for item in message_history]
        
    # 如果缓存中没有，从数据库中获取，并存入缓存
    messages = Message.objects.filter(user_id=user_id)
    message_history = []
    for message in messages:
        message_info = {
            "id": message.id,
            "content": message.content,
            "time": message.time.strftime("%Y-%m-%d %H:%M:%S")
        }
        message_history.append(message_info)
        
    redis.rpush("message_history_" + str(user_id), *[json.dumps(item) for item in message_history])
    
    return message_history

def process_order(order_id):
    lock_key = "order_lock_" + str(order_id)
    if redis.setnx(lock_key, 1):
        # 获取到锁，继续处理订单
        # ...
        # 处理完成后释放锁
        redis.delete(lock_key)
    else:
        # 未获取到锁，稍后重试或给出提示
    return

def publish_message(channel, message):
    redis.publish(channel, message)

def subscribe_channel(channel, callback):
    pubsub = redis.pubsub()
    pubsub.subscribe(channel)
    for item in pubsub.listen():
        if item['type'] == 'message':
            callback(item['data'])