import redis, json

r = redis.Redis()

MAX_LENGTH = 20
KEY = 'MESSAGES'

def add_message(user, msg):
    r.lpush(KEY, json.dumps(dict(user=user, msg=msg)))
    r.ltrim(KEY, 0, MAX_LENGTH-1)

def get_messages():
    rv = [json.loads(x) for x in r.lrange(KEY, 0, -1)]
    return rv