wrapper for appengine dev_appserver to execute cron jobs from cron.yaml

cron_appserver.py

# Needs libyaml and pyyaml installed
# on mac: brew install libyaml && pip install PyYAML 

import time, datetime, yaml, sys, os, subprocess, threading, requests, random, argparse, re

threads = []

parser = argparse.ArgumentParser()
parser.add_argument('-p', '--port', default='8080')
parser.add_argument('-a', '--address', default='localhost')
parser.add_argument('dir', nargs='?', default=os.getcwd())
args, extra = parser.parse_known_args()
root_url = 'http://%s:%s' % (args.address, args.port)

cron_pattern = re.compile('^every ([0-9]+) ([a-z]+)$')

def cron_task(config):

	# Simultaneous reqs crash appserver
	time.sleep(random.randrange(5,10))

	amount, unit = re.findall(cron_pattern, config['schedule'])[0]
	sleep_time = datetime.timedelta(**{unit: int(amount)}).seconds

	while True:
		try:
			requests.get(root_url + config['url'])
		except:
			pass
		time.sleep(sleep_time)

if os.path.isfile(os.path.join(args.dir, 'cron.yaml')):

	cron_config = yaml.load(open(os.path.join(args.dir, 'cron.yaml')))

	if 'cron' not in cron_config:

		print 'No cron entries'

	else:

		for entry in cron_config['cron']:
			
			threads.append(
				threading.Thread(target=cron_task, args=[entry])
			)
			threads[-1].daemon=True
			threads[-1].start()

print "Running dev_appserver.."

sys.argv[0] = 'dev_appserver.py'

subprocess.call(sys.argv)