Depado Depado - 1 year ago 75
Javascript Question

Update and render a value from Flask periodically

I want to display my CPU usage dynamically. I don't want to reload the page to see a new value. I know how to get the CPU usage in Python. Right now I render a template with the value. How can I continually update a page with a value from Flask?

def show_cpu():
cpu = getCpuLoad()
return render_template('show_cpu.html', cpu=cpu)

Answer Source

Using an Ajax request


@app.route('/_stuff', methods= ['GET'])
def stuff():
    return jsonify(cpu=cpu, ram=ram, disk=disk)


function update_values() {
            $SCRIPT_ROOT = {{ request.script_root|tojson|safe }};
                function(data) {
                    $("#cpuload").text(data.cpu+" %")
                    $("#ram").text(data.ram+" %")
                    $("#disk").text(data.disk+" %")

Using Websockets


# -*- coding: utf-8 -*-

# OS Imports
import json

# Local Imports
from app import sockets
from app.functions import get_cpu_load, get_disk_usage, get_vmem

def socket_system(ws):
    Returns the system informations, JSON Format
    CPU, RAM, and Disk Usage
    while True:
        message = ws.receive()
        if message == "update":
            cpu = round(get_cpu_load())
            ram = round(get_vmem())
            disk = round(get_disk_usage())
            ws.send(json.dumps(dict(received=message, cpu=cpu, ram=ram, disk=disk)))


# -*- coding: utf-8 -*-
from flask import Flask
from flask_sockets import Sockets

app = Flask(__name__)
sockets = Sockets(app)
from app import views

Using Flask-Websockets made my life a lot easier. Here is the launcher :


gunicorn -k flask_sockets.worker app:app

Finally, here is the client code :
The code is a bit too long, so here it is.
Note that I'm NOT using things like, that's why the code is long. This code also tries to reconnect to the server periodically, and can stop trying to reconnect on a user action. I use the Messenger lib to notify the user that something went wrong. Of course it's a bit more complicated than using but I really enjoyed coding the client side.

Recommended from our users: Dynamic Network Monitoring from WhatsUp Gold from IPSwitch. Free Download