110 lines
2.8 KiB
Python
110 lines
2.8 KiB
Python
# Copyright © 2020 Interplanetary Database Association e.V.,
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# BigchainDB and IPDB software contributors.
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# SPDX-License-Identifier: (Apache-2.0 AND CC-BY-4.0)
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# Code is Apache-2.0 and docs are CC-BY-4.0
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from queue import Empty
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from collections import defaultdict
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from multiprocessing import Queue
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POISON_PILL = 'POISON_PILL'
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class EventTypes:
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"""Container class that holds all the possible
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events BigchainDB manages.
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"""
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# If you add a new Event Type, make sure to add it
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# to the docs in docs/server/source/event-plugin-api.rst
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ALL = ~0
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BLOCK_VALID = 1
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BLOCK_INVALID = 2
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# NEW_EVENT = 4
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# NEW_EVENT = 8
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# NEW_EVENT = 16...
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class Event:
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"""An Event."""
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def __init__(self, event_type, event_data):
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"""Creates a new event.
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Args:
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event_type (int): the type of the event, see
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:class:`~bigchaindb.events.EventTypes`
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event_data (obj): the data of the event.
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"""
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self.type = event_type
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self.data = event_data
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class Exchange:
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"""Dispatch events to subscribers."""
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def __init__(self):
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self.publisher_queue = Queue()
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self.started_queue = Queue()
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# Map <event_types -> queues>
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self.queues = defaultdict(list)
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def get_publisher_queue(self):
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"""Get the queue used by the publisher.
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Returns:
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a :class:`multiprocessing.Queue`.
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"""
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return self.publisher_queue
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def get_subscriber_queue(self, event_types=None):
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"""Create a new queue for a specific combination of event types
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and return it.
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Returns:
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a :class:`multiprocessing.Queue`.
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Raises:
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RuntimeError if called after `run`
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"""
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try:
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self.started_queue.get(timeout=1)
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raise RuntimeError('Cannot create a new subscriber queue while Exchange is running.')
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except Empty:
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pass
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if event_types is None:
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event_types = EventTypes.ALL
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queue = Queue()
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self.queues[event_types].append(queue)
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return queue
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def dispatch(self, event):
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"""Given an event, send it to all the subscribers.
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Args
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event (:class:`~bigchaindb.events.EventTypes`): the event to
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dispatch to all the subscribers.
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"""
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for event_types, queues in self.queues.items():
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if event.type & event_types:
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for queue in queues:
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queue.put(event)
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def run(self):
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"""Start the exchange"""
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self.started_queue.put('STARTED')
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while True:
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event = self.publisher_queue.get()
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if event == POISON_PILL:
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return
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else:
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self.dispatch(event)
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