| # Licensed to the Apache Software Foundation (ASF) under one |
| # or more contributor license agreements. See the NOTICE file |
| # distributed with this work for additional information |
| # regarding copyright ownership. The ASF licenses this file |
| # to you under the Apache License, Version 2.0 (the |
| # "License"); you may not use this file except in compliance |
| # with the License. You may obtain a copy of the License at |
| # |
| # http://www.apache.org/licenses/LICENSE-2.0 |
| # |
| # Unless required by applicable law or agreed to in writing, |
| # software distributed under the License is distributed on an |
| # "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY |
| # KIND, either express or implied. See the License for the |
| # specific language governing permissions and limitations |
| # under the License. |
| |
| from Queue import Queue |
| |
| import threading |
| import paho.mqtt.client as mqtt |
| |
| from config import Config |
| |
| from modules.util.log import LogFactory |
| from modules.util.asyncscheduledtask import * |
| from modules.util.cartridgeagentutils import IncrementalCeilingListIterator |
| |
| |
| class EventSubscriber(threading.Thread): |
| """ |
| Provides functionality to subscribe to a given topic on the Stratos MB and |
| register event handlers for various events. |
| """ |
| |
| log = LogFactory().get_log(__name__) |
| |
| def __init__(self, topic, urls, username, password): |
| threading.Thread.__init__(self) |
| self.setDaemon(True) |
| |
| self.__event_queue = Queue(maxsize=0) |
| self.__event_executor = EventExecutor(self.__event_queue) |
| |
| self.__mb_client = None |
| self.__topic = topic |
| self.__subscribed = False |
| self.__urls = urls |
| self.__username = username |
| self.__password = password |
| self.setName("MBSubscriberThreadForTopic%s" % topic) |
| EventSubscriber.log.debug("Created a subscriber thread for %s" % topic) |
| |
| def run(self): |
| EventSubscriber.log.debug("Starting the subscriber thread for %s" % self.__topic) |
| # Start the event executor thread |
| self.__event_executor.start() |
| |
| """ |
| The following loop will iterate forever. |
| |
| When a successful connection is made, the failover() method returns. Then the |
| blocking method loop_forever() will be called on the connected mqtt client. This will only |
| return if disconnect() is called on the same client. If the connected message broker goes |
| down, the callback method on_disconnect() will call disconnect() on the connected client and the |
| loop_forever() method will return. The parent loop will be called again and this repeats |
| every time the message brokers are disconnected. |
| |
| This behavior guarantees that the subscriber is always subscribed to an available message |
| broker. |
| |
| """ |
| while True: |
| self.__mb_client = mqtt.Client() |
| self.__mb_client.on_connect = self.on_connect |
| self.__mb_client.on_message = self.on_message |
| self.__mb_client.on_disconnect = self.on_disconnect |
| if self.__username is not None: |
| EventSubscriber.log.info("Message broker credentials are provided.") |
| self.__mb_client.username_pw_set(self.__username, self.__password) |
| |
| # Select an online message broker and connect |
| self.__mb_client, connected_mb_ip, connected_mb_port = \ |
| EventSubscriber.failover(self.__urls, self.__mb_client) |
| |
| # update connected MB details in the config for the plugins to use |
| Config.mb_ip = connected_mb_ip |
| Config.mb_port = connected_mb_port |
| |
| EventSubscriber.log.info( |
| "Connected to the message broker with address %s:%s" % (connected_mb_ip, connected_mb_port)) |
| |
| self.__subscribed = True |
| |
| # Start blocking loop method |
| self.__mb_client.loop_forever() |
| |
| # Disconnected when the on_disconnect calls disconnect() on the client |
| self.__subscribed = False |
| EventSubscriber.log.debug("Disconnected from the message broker %s:%s. Reconnecting..." |
| % (connected_mb_ip, connected_mb_port)) |
| |
| def register_handler(self, event, handler): |
| """ |
| Adds an event handler function mapped to the provided event. |
| :param str event: Name of the event to attach the provided handler |
| :param handler: The handler function |
| :return: void |
| :rtype: void |
| """ |
| self.__event_executor.register_event_handler(event, handler) |
| EventSubscriber.log.debug("Registered handler for event %r" % event) |
| |
| def on_connect(self, client, userdata, flags, rc): |
| if rc != 0: |
| EventSubscriber.log.debug("Connection to the message broker didn't succeed. Disconnecting client.") |
| client.disconnect() |
| return |
| |
| EventSubscriber.log.debug("Connected to message broker %s:%s successfully." % (client._host, client._port)) |
| self.__mb_client.subscribe(self.__topic) |
| EventSubscriber.log.debug("Subscribed to %r" % self.__topic) |
| |
| def on_message(self, client, userdata, msg): |
| EventSubscriber.log.debug("Message received: %s:\n%s" % (msg.topic, msg.payload)) |
| self.__event_queue.put(msg) |
| |
| def on_disconnect(self, client, userdata, rc): |
| EventSubscriber.log.debug("Message broker client disconnected. %s:%s" % (client._host, client._port)) |
| if rc != 0: |
| client.disconnect() |
| |
| def is_subscribed(self): |
| """ |
| Checks if this event subscriber is successfully subscribed to the provided topic |
| :return: True if subscribed, False if otherwise |
| :rtype: bool |
| """ |
| return self.__subscribed |
| |
| @staticmethod |
| def failover(mb_urls, mb_client): |
| """ |
| Iterate through the list of message brokers provided and connect to the first available server. This will not |
| return until a message broker connection is established. |
| |
| :param mb_urls: the list of message broker URLS of format [host:port, host:port] |
| :param mb_client: the initialized message broker client object |
| :return: a tuple of the connected message broker client, connected message broker IP address and connected |
| message broker port |
| |
| """ |
| # Connection retry interval incrementer |
| message_broker_retry_timer = IncrementalCeilingListIterator( |
| [2, 2, 5, 5, 10, 10, 20, 20, 30, 30, 40, 40, 50, 50, 60], |
| False) |
| |
| # Cycling through the provided mb urls until forever |
| while True: |
| retry_interval = message_broker_retry_timer.get_next_retry_interval() |
| |
| for mb_url in mb_urls: |
| mb_ip, mb_port = mb_url.split(":") |
| EventSubscriber.log.debug( |
| "Trying to connect to the message broker with address %r:%r" % (mb_ip, mb_port)) |
| try: |
| mb_client.connect(mb_ip, mb_port, 60) |
| return mb_client, mb_ip, mb_port |
| except: |
| # The message broker didn't respond well |
| EventSubscriber.log.info("Could not connect to the message broker at %s:%s." % (mb_ip, mb_port)) |
| |
| EventSubscriber.log.error( |
| "Could not connect to any of the message brokers provided. Retrying in %s seconds." % retry_interval) |
| |
| time.sleep(retry_interval) |
| |
| |
| class EventExecutor(threading.Thread): |
| """ |
| Polls the event queue and executes event handlers for each event |
| """ |
| def __init__(self, event_queue): |
| threading.Thread.__init__(self) |
| self.setDaemon(True) |
| self.__event_queue = event_queue |
| self.__event_handlers = {} |
| EventSubscriber.log = LogFactory().get_log(__name__) |
| self.setName("MBEventExecutorThread") |
| EventSubscriber.log.debug("Created an EventExecutor") |
| |
| def run(self): |
| EventSubscriber.log.debug("Starting an EventExecutor") |
| while True: |
| event_msg = self.__event_queue.get() |
| event = event_msg.topic.rpartition('/')[2] |
| if event in self.__event_handlers: |
| handler = self.__event_handlers[event] |
| try: |
| EventSubscriber.log.debug("Executing handler for event %r" % event) |
| handler(event_msg) |
| except Exception as err: |
| EventSubscriber.log.exception("Error processing %r event: %s" % (event, err)) |
| else: |
| EventSubscriber.log.debug("Event handler not found for event : %r" % event) |
| |
| def register_event_handler(self, event, handler): |
| self.__event_handlers[event] = handler |
| |
| def terminate(self): |
| self.terminate() |
