[英]How to asynchrony get a real time data from redis by using python flask socket.io and threads?
我的程序從傳感器收集數據,並將該數據發送到Web界面,該界面以實時圖形的形式顯示並向后發送一些命令。
問題是數據發送有很大的延遲或發送了舊數據。 我應該更改以兩種方式異步發送數據嗎?
我簡化了代碼。 示例1,當數據在幾分鍾內到達一次時:
# System stuff
import os
import sys
import serial
# Multiprocessing
from multiprocessing import Process
from threading import Thread # for same memory
import timeit
from time import sleep
# database
import redis
# Web server
from flask import Flask, render_template
from flask_socketio import SocketIO, emit, send, join_room, leave_room, close_room, rooms, disconnect
# Config
DEBUG = True
db = redis.StrictRedis(host='localhost', port=6379, db=0)
#db vars
db.set('velocity', 0.0)
db.set('distance', 0.0)
def webServer(db):
app = Flask(__name__)
app.config['SECRET_KEY'] = 'secret!'
socketio = SocketIO(app)
@app.route('/')
def index():
return render_template('index.html')
def exchangeData():
prev_distance = 0.00
while(True):
distance = round(float(db.get('distance')), 2)
if(distance != prev_distance):
velocity = round(float(db.get('velocity')), 2)
distance = round(float(db.get('distance')), 2)
socketio.emit('exchangeData', {
'velocity': velocity,
'distance': distance,
})
prev_distance = distance
print("DATA sended: %s m/s" % velocity)
sleep(0.2)
@socketio.on('connect')
def test_connect():
t_exchangeData = Thread(target=exchangeData).start()
socketio.run(app, debug=True, host="0.0.0.0")
def newData(db):
c = 0.00
while(True):
db.set('velocity', c)
db.set('distance', c)
c += 1.00
sleep(1)
if __name__ == '__main__':
p_newData = Process(target=newData, args=(db,)).start()
p_webServer = Process(target=webServer, args=(db,)).start()
#p_checkConnection = Process(target=checkConnection, args=(db, HOSTNAME, pinglog)).start()
#p_calcVD = Process(target=calcVD, args=(db,)).start()
在瀏覽器中,我的等待時間約為2分鍾:
Object {velocity: 218, distance: 218}
// two minutes later
Object {velocity: 306, distance: 306}
// two minutes later
Object {velocity: 306, distance: 306}
示例2,當我不使用if語句和sleep時:
# System stuff
import os
import sys
import serial
# Multiprocessing
from multiprocessing import Process
from threading import Thread # for same memory
import timeit
from time import sleep
# database
import redis
# Web server
from flask import Flask, render_template
from flask_socketio import SocketIO, emit, send, join_room, leave_room, close_room, rooms, disconnect
# Config
DEBUG = True
db = redis.StrictRedis(host='localhost', port=6379, db=0)
#db vars
db.set('velocity', 0.0)
db.set('distance', 0.0)
def webServer(db):
app = Flask(__name__)
app.config['SECRET_KEY'] = 'secret!'
socketio = SocketIO(app)
@app.route('/')
def index():
return render_template('index.html')
def exchangeData():
prev_distance = 0.00
while(True):
#distance = round(float(db.get('distance')), 2)
#if(distance != prev_distance):
velocity = round(float(db.get('velocity')), 2)
distance = round(float(db.get('distance')), 2)
socketio.emit('exchangeData', {
'velocity': velocity,
'distance': distance,
})
prev_distance = distance
print("DATA sended: %s m/s" % velocity)
#sleep(0.2)
@socketio.on('connect')
def test_connect():
t_exchangeData = Thread(target=exchangeData).start()
socketio.run(app, debug=True, host="0.0.0.0")
def newData(db):
c = 0.00
while(True):
db.set('velocity', c)
db.set('distance', c)
c += 1.00
sleep(1)
if __name__ == '__main__':
p_newData = Process(target=newData, args=(db,)).start()
p_webServer = Process(target=webServer, args=(db,)).start()
#p_checkConnection = Process(target=checkConnection, args=(db, HOSTNAME, pinglog)).start()
#p_calcVD = Process(target=calcVD, args=(db,)).start()
在這種情況下,我實時獲取數據,但它是相同的數據,並且在幾分鍾內僅更改一次:
Object {distance: 3, velocity: 3}
Object {distance: 3, velocity: 3}
Object {distance: 3, velocity: 3}
// repeating around 2 minutes
Object {distance: 357, velocity: 357}
// repeating again...
主要問題是我沒有添加這兩行:
import eventlet
eventlet.monkey_patch()
另外,當我嘗試尋找解決方案時,當我從while循環外的redis調用數據時犯了一個錯誤。
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