python-awips/awips/dataaccess/PyNotification.py

##
# This software was developed and / or modified by Raytheon Company,
# pursuant to Contract DG133W-05-CQ-1067 with the US Government.
#
# U.S. EXPORT CONTROLLED TECHNICAL DATA
# This software product contains export-restricted data whose
# export/transfer/disclosure is restricted by U.S. law. Dissemination
# to non-U.S. persons whether in the United States or abroad requires
# an export license or other authorization.
#
# Contractor Name:        Raytheon Company
# Contractor Address:     6825 Pine Street, Suite 340
#                         Mail Stop B8
#                         Omaha, NE 68106
#                         402.291.0100
#
# See the AWIPS II Master Rights File ("Master Rights File.pdf") for
# further licensing information.
##

#
# Implements IData for use by native Python clients to the Data Access
# Framework.
#
# SOFTWARE HISTORY
#
# Date          Ticket#  Engineer     Description
# ------------- -------- ------------ --------------------------------------------
# Jun 22, 2016  2416     rjpeter      Initial creation
# Jul 22, 2016  2416     tgurney      Finish implementation
# Sep 07, 2017  6175     tgurney      Override messageReceived in subclasses
# Nov 05, 2019  7884     tgurney      Fix in subscribed()
# Jun 24, 2020  8187     randerso     Added program for qpid connection_id
#


import abc

from ufpy.dataaccess import DataAccessLayer
from ufpy.dataaccess import INotificationSubscriber
from ufpy.QpidSubscriber import QpidSubscriber
from dynamicserialize.dstypes.com.raytheon.uf.common.time import DataTime


class PyNotification(INotificationSubscriber, metaclass=abc.ABCMeta):
    """
    Receives notifications for new data and retrieves the data that meets
    specified filtering criteria.
    """

    def __init__(self, request, filter, host='localhost', port=5672, requestHost='localhost', program="PyNotification"):
        self.DAL = DataAccessLayer
        self.DAL.changeEDEXHost(requestHost)
        self.request = request
        self.notificationFilter = filter
        self.host = host
        self.port = port
        self.program=program
        self.__topicName = "edex.alerts"
        self.callback = None

    def subscribe(self, callback):
        """
        Start listening for notifications.

        Args:
            callback: Function to call with a list of received data objects.
              Will be called once for each request made for data.
        """
        assert hasattr(callback, '__call__'), 'callback arg must be callable'
        self.callback = callback
        self.qs = QpidSubscriber(host=self.host, port=self.port, decompress=True, program=self.program)
        self.qs.topicSubscribe(self.__topicName, self.messageReceived)
        # Blocks here

    def close(self):
        self.qs.close()

    def getDataTime(self, dataURI):
        dataTimeStr = dataURI.split('/')[2]
        return DataTime(dataTimeStr)

    @abc.abstractmethod
    def messageReceived(self, msg):
        """Called when a message is received from QpidSubscriber.

        This method must call self.callback once for each request made for data
        """
        pass

    @abc.abstractmethod
    def getData(self, request, dataTimes):
        """
        Retrieve and return data

        Args:
            request: IDataRequest to send to the server
            dataTimes: list of data times
        Returns:
            list of IData
        """
        pass

    @property
    def subscribed(self):
        """True if currently subscribed to notifications."""
        try:
            return self.qs.queueStarted
        except AttributeError:
            return False