producer/consumerlocator.py

#!/usr/bin/env python

import datetime
import communicator

"""
Consumer locator modul, that manages the list of consumers.
"""

__author__ = "@dscharnitzky"
__copyright__ = "Copyright 2020, GoldenPogácsa Team"
__module_name__ = "consumerlocator"
__version__text__ = "1"


class ConsumerLocator:

    """
    Manages the list of consumers.
    """

    def __init__(self):
        """
        Initialize class.
        """
        self.consumerList = [{"Host": "KnownHost", "State": True, "LastOk": datetime.datetime.now()}]
        self.currentConsumer = self.consumerList[0]["Host"]

    def initCommunicator(self,  comm: communicator.Communicator):
        self.communicator = comm

    def learnconsumerlist(self):
        """"
        Learns the list of consumers.
        """
        recievedconsumerlist = self.communicator.discoveravailableconsumers()
        if recievedconsumerlist is None:
            return
        for consumer in recievedconsumerlist:
            self.consumerList.append({"Host": consumer, "State": True, "LastOk": datetime.datetime.now()})
        self.updateConsumerList()

    def updateconsumerlist(self):
        """
        Updates the consumer list based on their availability.
        """
        removeList = []
        for consumer in self.consumerList:
            if not self.communicator.checkconsumer(consumer["Host"]):
                consumer["State"] = False
                if datetime.datetime.now() - consumer["LastOk"] > datetime.timedelta(hours=1):
                    removeList.append(consumer)
            else:
                consumer["LastOk"] = datetime.datetime.now()
        for rem in removeList:
            self.consumerList.remove(rem)

    def updateconsumer(self):
        """
        Checks all the consumers in the list and updates the current consumer if necessary.
        :return: the current consumer or None if there are no available customers at the moment.
        """
        self.updateConsumerList()

        if not self.checkConsumer():

            newCurrentConsumer = None

            for consumer in self.consumerList:
                if consumer["State"]:
                    newCurrentConsumer = consumer
                    break

            self.currentConsumer = newCurrentConsumer
            self.learnconsumerlist()

        if self.currentConsumer is not None:
            return self.currentConsumer["Host"]
        else:
            return None

    def getcurrentconsumer(self):
        """
        Returns the currently selected consumer.
        :return: the current consumer
        """
        return self.currentConsumer["Host"]

    def checkcurrentconsumer(self):
        """
        Check the consumers health.
        :return: True if OK, False if fail
        """
        if self.communicator.checkconsumer(self.currentConsumer["Host"]):
            return True
        else:
            return False