updog/helpers.py

import threading
import time

# Threaded repeating timer thing
# From https://stackoverflow.com/a/40965385/16432246
# It shouldn't drift, but that's untested
# Keep in mind you can't catch Exceptions for this, it just crashes the thread.
# Some more scheduling stuff: https://www.redwood.com/article/python-job-scheduling/


class RepeatedTimer(object):
    '''
    Run stuff repeatedly every x seconds
    Example usage (from SO and ported to Python 3):
    from time import sleep

      def hello(name):
          print(f'Hello {name}!')

      print()"starting...")
      rt = RepeatedTimer(1, hello, "World") # it auto-starts, no need of rt.start()
      try:
          sleep(5) # your long-running job goes here...
      except:
          rt.stop() # better in a try/catch block to make sure the program ends!
    '''

    def __init__(self, interval, function, *args, **kwargs):
        '''
        Run a functions with arguments every 
        '''
        self._timer = None
        self.interval = interval
        self.function = function
        self.args = args
        self.kwargs = kwargs
        self.is_running = False
        self.next_call = time.time()
        self.start()

    def _run(self):
        self.is_running = False
        self.start()
        self.function(*self.args, **self.kwargs)

    def start(self):
        if not self.is_running:
            self.next_call += self.interval
            self._timer = threading.Timer(
                self.next_call - time.time(), self._run)
            self._timer.start()
            self.is_running = True

    def stop(self):
        self._timer.cancel()
        self.is_running = False


def create_instances(config, checkers, alerts, logging):
    '''
    Creates instances of all the extensions according to config
    Parameters:
        config: the dictionary containing the config
    Returns:
        instances (dict): A dictionary containing instances of the extensions
            example: {'site': {'checker': instanceOfCheckerTemplate}}
    '''
    instances = {}
    
    # global arguments
    default_checker = ''
    default_alerter = ''
    default_logger = ''
    for service in config.keys():
        
        if service == 'global-args':
            default_checker = config['global-args'].get('default-checker', '')
            default_alerter = config['global-args'].get('default-alerts', '')
            default_logger = config['global-args'].get('default-logging', '')
            continue
        instances[service] = {}
        # create an instance of checker with the arguments for them, including the optional `default-checker`
        checker_args = config[service]['checker-args']
        if config[service].get('checker', '') != '':
            checker = config[service]['checker']
        else:
            checker = default_checker

        instances[service]['checker'] = checkers[checker](checker_args)

        # and for alerts
        alerter_args = config[service]['alerts-args']
        if config[service].get('alerts', '') != '':
            alerter = config[service]['alerts']
        else:
            alerter = default_alerter

        instances[service]['alerts'] = alerts[alerter](alerter_args)

        # and for logging
        logger_args = config[service]['logging-args']
        if config[service].get('logging', '') != '':
            logger = config[service]['logging']
        else:
            logger = default_logger

        instances[service]['logging'] = logging[logger](logger_args)

    return instances


def run_check(service_name, checker, alerts, logging):
    '''
    Does the logic and stuff for running the checker, calling alerts/logging, and so on
    '''
    status = checker.get_status()
    return_codes = checker.get_return_codes()
    status_message = return_codes[status]
    logging.log(service_name, status, status_message)
    alerts.alert(service_name, status, status_message)