我已經使用socketio創建了一個小的Flask webapp,它應該可視化一個brew控制器。硬件是Raspberry Pi,控制器部分(硬件綁定和數據收集)是在獨立的後臺線程中完成的,該線程在create_app
開始。我需要確保後臺線程只開始一次(即使我創建了多個應用程序對象)。所以我使用BrewController.get_instance()
函數來實現某種單例模式。後臺線程用Flask-Socketio啓動兩次
import os
import time
import threading
import arrow
from sqlitedict import SqliteDict
from flask import Flask
from flask_bootstrap import Bootstrap
from flask_socketio import SocketIO
from flaskext.lesscss import lesscss
from config import config
from .brewcontroller import BrewController
background_thread = threading.Thread()
# Flask Plugins
bootstrap = Bootstrap()
socketio = SocketIO()
brew_controller = BrewController.get_instance()
db = SqliteDict('process_data.sqlite', tablename='pd', autocommit=False)
db.setdefault('t', [])
db.setdefault('temp_sp', [])
db.setdefault('temp_ct', [])
db.setdefault('ht_pwr', [])
db.commit()
from . import events # noqa
def create_app(config_name=None):
app = Flask(__name__)
if config_name is None:
config_name = os.environ.get('PIBREW_CONFIG', 'development')
app.config.from_object(config[config_name])
# init flask plugins
lesscss(app)
bootstrap.init_app(app)
socketio.init_app(app)
# create blueprints
from .main import main as main_blueprint
app.register_blueprint(main_blueprint, url_prefix='/')
# init the brew controller and start the background task if none
# exists yet
print(brew_controller)
if not brew_controller.initialized:
brew_controller.init_app(app)
background_thread = threading.Thread(
target=process_controller,
args=[app.config['PROCESS_INTERVAL']],
daemon=True
)
print('controller started')
background_thread.start()
return app
def process_controller(interval):
while(1):
current_time = arrow.now()
brew_controller.process()
data = {
't': current_time.format('HH:mm:ss'),
'temp_sp': '{:.1f}'.format(brew_controller.temp_setpoint),
'temp_ct': '{:.1f}'.format(brew_controller.temp_current),
'ht_en': brew_controller.heater_enabled,
'mx_en': brew_controller.mixer_enabled,
'ht_pwr': '{:.1f}'.format(brew_controller.heater_power_pct),
'ht_on': brew_controller.heater_on,
}
x = db['t']
x.append(data['t'])
db['t'] = x
db['temp_sp'].append(data['temp_sp'])
db['temp_sp'] = db['temp_sp']
db['temp_ct'].append(data['temp_ct'])
db['temp_ct'] = db['temp_ct']
db['ht_pwr'].append(data['ht_pwr'])
db['ht_pwr'] = db['ht_pwr']
db.commit()
socketio.emit('update', data)
time.sleep(interval)
但是線程仍然開始兩次,我甚至得到兩個不同的BrewController實例。所以我最終得到了兩倍於我的數據庫和重複值的數據。
後,我打電話manage.py運行看起來像這樣(我打印的brewcontroller實例,看看它們是不同的)輸出:
<pibrew.brewcontroller.BrewController object at 0x105777208>
<pibrew.brewcontroller.BrewController object at 0x105777208>
controller started
* Restarting with stat
<pibrew.brewcontroller.BrewController object at 0x10ca04240>
<pibrew.brewcontroller.BrewController object at 0x10ca04240>
controller started
* Debugger is active!
* Debugger pin code: 121-481-821
(31213) wsgi starting up on http://0.0.0.0:5000
我發現通過設置use_reloader
說法,我可以抑制這個我manage.py爲False。
@manager.command
def run():
app = create_app()
socketio.run(app, host='0.0.0.0', port=5000, use_reloader=False)
但是,首先這種雙重啓動的原因是什麼。對我來說,似乎有兩個創建的進程。有人可以解釋發生了什麼,以及防止這種情況的最佳方法是什麼。
我喜歡使用'before_first_request'處理程序的想法。但是我仍然有點麻煩,因爲我不知道該把它放在哪裏。當我使用工廠函數'create_app'時,模塊中沒有可用的應用程序對象。我也無法註冊藍圖。 – MrLeeh
您可以在藍圖上使用[before_app_first_request](http://flask.pocoo.org/docs/0.11/api/#flask.Blueprint.before_app_first_request)。 – Miguel