"""Ticker extension for Flask."""
import struct
from flask import current_app
from eventlet import spawn_n
from eventlet.green import zmq
# Context are thread safe already,
# we'll create one global one for all sockets
context = zmq.Context()
class Ticker:
"""Handle ZMQ connection to broker."""
def __init__(self, app=None, socketio=None):
self.app = app
self.socketio = socketio
if app is not None:
self.init_app(app)
spawn_n(self.run) # spawns eventlet co-routine
@staticmethod
def init_app(app):
"""Initialise extension."""
app.config.setdefault('TICKER_URL', "tcp://localhost:7000")
# We want the connection live forever
# app.teardown_appcontext(self.teardown)
def run(self):
"""Connect to ticker server and emit updates."""
socket = context.socket(zmq.SUB)
# Set topic filter, this is a binary prefix
# to check for each incoming message
# set from server as uchar topic = X
# We'll subsribe to only tick updates for now
socket.setsockopt(zmq.SUBSCRIBE, bytes.fromhex('00'))
with self.app.app_context():
current_app.logger.debug("Connecting to ticker: %s", current_app.config['TICKER_URL'])
socket.connect(current_app.config['TICKER_URL'])
while True:
raw = socket.recv()
# unpack bytes https://docs.python.org/3/library/struct.html
bid, ask = struct.unpack_from('dd', raw, 1) # offset topic
self.socketio.emit('tick', {'bid': round(bid, 5), 'ask': round(ask, 5)})
# socket will be cleaned up at garbarge collection
