cache.py

#!/usr/bin/env python3

import sys
from timeit import default_timer as timer
import zmq
import time
import signal
import logging
import helpers
import yaml

# Load config
with open("/home/pi/.development/the-cake-can-wait/config.yaml", "r") as configfile:
    config = yaml.safe_load(configfile)

# Constants
cache_period = config["user_cache"]["cache_period"]
scanner_endpoint = config["general"]["scanner_endpoint"]
prehook_endpoint = config["general"]["prehook_endpoint"]

#Logging setup 
helpers.setup_logging()
logger = logging.getLogger("user_cache")

logger.debug("Setting up sockets")
context = zmq.Context() 
subscriber = context.socket(zmq.SUB)
subscriber.connect(scanner_endpoint)
subscriber.setsockopt(zmq.SUBSCRIBE, b'')
subscriber.setsockopt(zmq.CONFLATE, 1)

prehook = context.socket(zmq.REP)
prehook.bind(prehook_endpoint)

def fexit(signal,frame):
    subscriber.close()
    prehook.close()
    context.term()
    logger.info("Terminating cache.")
    sys.exit(0)

signal.signal(signal.SIGINT, fexit)

poller = zmq.Poller()
poller.register(subscriber, zmq.POLLIN)
poller.register(prehook, zmq.POLLIN)

release = 0
uid = None
while True:
    socks = dict(poller.poll(1000))
    logger.debug("Socket poll returned %s", socks)
    if subscriber in socks and socks[subscriber] == zmq.POLLIN:
        uid = subscriber.recv_pyobj()
        release = timer() + cache_period
        logger.debug("Received new uid: %s | Release time is %s", uid, release)
    if prehook in socks and socks[prehook] == zmq.POLLIN:
        logger.debug("Received request from prehook")
        prehook.recv_pyobj()
        reply = uid if uid != None else 0
        logger.debug("Sending reply to prehook")
        prehook.send_pyobj(reply)
        uid = None
        release = 0
    
    time.sleep(0.2)
    if release != 0 and timer() > release:
        logger.debug("Releasing cached uid")
        uid = None
        release = 0