app.py

from redis import from_url as redis_from_url


def create_api(app):
    access_key_id = app.config["AMAZON_ACCESS_KEY"]
    secret_access_key = app.config["AMAZON_SECRET_KEY"]
    associate_tag = app.config["AMAZON_ASSOCIATE_TAG"]
    locale = app.config["AMAZON_LOCALE"]
    redis = redis_from_url(app.config["AMAZON_REDIS_URL"])

    # use str() casts to prevent str.translate() from failing inside
    # amazonproduct.API -> _fetch -> hmac
    return SynchronizedAPI(
        redis=redis,
        access_key_id=str(access_key_id),
        associate_tag=str(associate_tag),
        locale=str(locale),
        secret_access_key=str(secret_access_key))

synchronized_api.py

import time
from datetime import datetime

from redis.client import Lock


class SynchronizedAPI(API):
    def __init__(self, *args, **kwargs):
        self.redis = kwargs.pop('redis')
        super(SynchronizedAPI, self).__init__(*args, **kwargs)

    def _fetch(self, url):
        with Lock(self.redis, "SynchronizedAPI.lock", timeout=10):
            # Read shared lastcall
            last_call = self.redis.get("SynchronizedAPI.lastcall")
            if last_call:
                self.last_call = datetime.fromtimestamp(float(last_call))

            # Actual work
            result = super(SynchronizedAPI, self)._fetch(url)

            # Store shared lastcall
            last_call = time.mktime(self.last_call.timetuple())
            self.redis.set("SynchronizedAPI.lastcall", str(last_call))

            return result