user6066403 user6066403 - 16 days ago 5
Python Question

How to exec periodically a function in CherryPy

This code generate 3 webpages using CheryPy. It's works but now i need to execute periodically the function "PageWeb" to have last informations from a query.
How to use threading in CherryPy:

from Widget import showLine
from Widget import SocketLivestatus
import cherrypy
import threading


def PageWeb(cluster):
# Open Socket
table = SocketLivestatus(['host1','host2'], 50000, cluster)
# Result
Line = showLine(table)
HTML = '''<!doctype html>
<html lang="en">
<head><meta charset="utf-8">
<title>Widget</title>
<link rel="stylesheet" href="css/font-awesome.min.css">
</head>
<body style="background-color: #1F1F1F">'''+Line+'''</body>
</html>'''
return HTML

#BEFORE
re7 = PageWeb("re7")
prod1 = PageWeb("prod1")
prod2 = PageWeb("prod2")
#MY GOAL
re7 = threading.Timer(5.0, PageWeb("re7")).start()
prod1 = threading.Timer(5.0, PageWeb("prod1")).start()
prod2 = threading.Timer(5.0, PageWeb("prod2")).start()


class HelloWorld(object):
@cherrypy.expose
def re7(self):
return re7

@cherrypy.expose
def prod1(self):
return prod1

@cherrypy.expose
def prod2(self):
return prod2



if __name__ == '__main__':
cherrypy.config.update(
{'server.socket_host': '0.0.0.0'} )
cherrypy.quickstart(HelloWorld(),config={
'/':
{ 'tools.staticdir.on':True,
'tools.staticdir.dir': "/app"
}
# '/fonts':
# { 'tools.staticdir.on':True,
# 'tools.staticdir.dir': "/app"
# }
})


The problem is about threading.Timer(5.0, PageWeb("...")).start() return an error:

Traceback (most recent call last):
File "/usr/lib64/python2.7/threading.py", line 811, in __bootstrap_inner
self.run()
File "/usr/lib64/python2.7/threading.py", line 1083, in run
self.function(*self.args, **self.kwargs)
TypeError: 'str' object is not callable


I would like help to use threading function in CherryPy.

Answer

A threading.Timer only runs once:

This class represents an action that should be run only after a certain amount of time has passed

After some experimentation, it appears that cherrypy does not work well with threads. The following code uses the multiprocessing library to create a separate Process. The HTML is shared by storing it as the first entry of a managed list:

import cherrypy
import multiprocessing
import time

def PageWeb(cluster, sleep_interval, lock, shared_result):
    counter = 0
    while True:
        HTML = '''<!doctype html>
                 <html lang="en">
                    <head><meta charset="utf-8">
                     <title>Widget</title>
                     <link rel="stylesheet" href="css/font-awesome.min.css">
                 </head>
                <body style="background-color: #1F1F1F">'''+str(counter)+'''</body>
                </html>'''
        counter += 1
        with lock:
            shared_result[0] = HTML
        time.sleep(sleep_interval)

class HelloWorld(object):
    def __init__(self):
        self.re7_lock = multiprocessing.Lock()
        self.manager = multiprocessing.Manager()
        self.re7_result = self.manager.list()
        self.re7_result.append('')
        arg_list = ("re7", 5.0, self.re7_lock, self.re7_result)
        self.re7_process = multiprocessing.Process(target=PageWeb, args=arg_list)
        self.re7_process.daemon = True
        self.re7_process.start()

    @cherrypy.expose
    def re7(self):
        with self.re7_lock:
            return str(self.re7_result[0])

cherrypy.quickstart(HelloWorld())

This code is a minimal, complete, and verifiable example. You should be able to integrate it with your code.

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