example of using redis with python

python_redis_example.py

import redis
import redis.sentinel

import logging

# TODO: would be useful to also
def discover_redis_master(sentinel_addrs, redis_name):
    """Use listed sentinels to find the redis master
    """
    sentinel = redis.sentinel.Sentinel(sentinel_addrs, socket_timeout=0.1)

    master_addr = sentinel.discover_master(redis_name)

    redis_client = sentinel.master_for(redis_name, socket_timeout=0.1)

    if redis_client.ping():
        return redis_client, master_addr
    else:
        raise Exception("failed to ping redis master")


class SignupState:
    CHKSUM_FAILED = "chksum mismatch"
    NO_SUCH_REQUEST = "no such request"
    ALREADY_VERIFIED = "already verified"
    BACKEND_ERROR = "backend error"
    SUCCESS = "success"
    NOT_PENDING = "not pending"

# TODO: add enum here (as class) for signup status

# Attempt to update a redis signup record, to indicate that the user has clicked
# in order to verify the signup.


def update_signup_record_to_verified(r, user_key, user_chksum):
    stored_obj = r.hgetall(user_key)
    if not stored_obj:
        logging.warning("{}: signup request not found".format(user_key))
        return SignupState.NO_SUCH_REQUEST

    status = stored_obj[b'status'].decode('utf-8')
    chksum = stored_obj[b'chksum'].decode('utf-8')

    # Check the user provided checksum matches the signup checksum.  This is
    # needed so that an invalid (spoofing?) attempt to validate a signup account
    # can be detected. So for signup to be successful, the user needs to new the
    # signup key (which is guessable), the encoding key, and the original record
    # checksum.
    if user_chksum != chksum:
        logging.warn("verify failed; chksum mismatch")
        return SignupState.CHKSUM_FAILED

    # TODO: return error codes in here, instead of exceptions
    if (status == 'pending'):
        rv = r.hset(user_key, 'status', 'verified')
        if rv == 0:
            logging.info("{}: signup status set to verified".format(user_key))
            # TODO: here, set the state to 'verified'
            return SignupState.SUCCESS
        else:
            logging.warn("hset expectedly returned value {}".format(rv))
            return SignupState.BACKEND_ERROR
    else:
        logging.warn(
            "{}: sign-up request is not in pending state, so cannot progress to verified; current state is '{}'".format(user_key, status))
        return SignupState.NOT_PENDING


def get_global_id_block(r, key, blocksize=100):
    """Reserve a block of global id numbers.

The usable inclusive range is returned in the tuple as (lower,upper).

    """
    assert isinstance(key, str)
    assert isinstance(blocksize, int)
    upper = r.incrby(key, max(blocksize, 1))
    #lower = max(1, upper-blocksize)  # min valid id is 1
    return (upper-blocksize, upper-1)