Develop Reference

Are there any better ways to run uvicorn in thread?

Uvicorn will not run inside thread because signals don't work in threads.
Just removing the signal handling stops server from closing (needs to be forcefully shut down)
My solution was interferring with the __new__ function to get the server object and creating a shutdown function, and then binding that to a signal outside the thread.
However this is a really ugly solution. Are there better ways?
def run():
'''
Start uvicorn server
returns exit function
'''
server = None
old_new = uvicorn.Server.__new__
def spoof_server(self, *_, **__):
'''Interfeer with __new__ to set server'''
nonlocal server
server = old_new(self)
return server
uvicorn.Server.__new__ = spoof_server
uvicorn.Server.install_signal_handlers = lambda *_, **__: None
Thread(target=uvicorn.run, args=[make_app()]).start()
def exit_server():
print('exiting...')
server.handle_exit(None, None)
return exit_server

I was looking for something like this as well. I found this answer that helped me.
https://stackoverflow.com/a/64521239/13029591
I'll post the snippet here:
import contextlib
import time
import threading
import uvicorn
class Server(uvicorn.Server):
def install_signal_handlers(self):
pass
#contextlib.contextmanager
def run_in_thread(self):
thread = threading.Thread(target=self.run)
thread.start()
try:
while not self.started:
time.sleep(1e-3)
yield
finally:
self.should_exit = True
thread.join()
config = Config("example:app", host="127.0.0.1", port=5000, log_level="info")
server = Server(config=config)
with server.run_in_thread():
# Server is started.
...
# Server will be stopped once code put here is completed
...
# Server stopped.

Tkinter Threading causing UI freeze

I've searched this site (and others) up and down but I can't seem to find the right solution.
I have a client program that connects to a server and automatically sends a message every few seconds, as well as on user command. I'm using multiple threads for this.
Enter Tkinter: Once I hit the 'Connect' button, my UI freezes, either until the connection attempt times out or until the end of time, should the client connect to the server.
I've tried calling the thread from the button's command parameter, from inside the main loop, and outside the main loop. I've tried putting the main loop in a thread and then creating a new thread for the connection from there.
Nothing seems to be working...the UI continues to hang.
class EventSim(Frame):
def __init__(self, parent):
self.queue = Queue
Frame.__init__(self, parent)
self.parent = parent
def initUI(self,IP_Address,Port_Number,Events_Directory):
#...
self.Con_Button = Button(frame7,text='Connect', command = lambda:
self.connect(IP_Text.get(),Port_Text.get(),))
def connect(self,IP,Port):
ConnectionThread = Thread(eventsim.con_thread(IP,Port))
ConnectionThread.start()
def main():
root = Tk()
root.geometry("300x310+750+300")
Sim = EventSim(root)
eventsim.readconfig()
Sim.initUI(eventsim.ipa,eventsim.portnum,eventsim.event_dir)
root.mainloop()

You pass the result of eventsim.con_thread(IP,Port) to Thread(...) function, so it will wait until the execution of eventsim.con_thread(...) completes. Try changing:
def connect(self, IP, Port):
ConnectionThread = Thread(eventsim.con_thread(IP,Port))
ConnectionThread.start()
to:
def connect(self, IP, Port):
ConnectionThread = Thread(target=lambda ip=IP, port=Port: eventsim.con_thread(ip,port))
ConnectionThread.start()

Run WebSocket server in Thread

this is probably more a question about threading than about my websocket.
I'm using "SimpleWebSocket" from github ( https://github.com/dpallot/simple-websocket-server )
The example works fine:
from SimpleWebSocketServer import SimpleWebSocketServer, WebSocket
class SimpleEcho(WebSocket):
def handleMessage(self):
# echo message back to client
self.sendMessage(self.data)
def handleConnected(self):
print self.address, 'connected'
def handleClose(self):
print self.address, 'closed'
server = SimpleWebSocketServer('', 8000, SimpleEcho)
server.serveforever()
The Server is running, I can connect and send Messages.
Now i try to run it as a Thread with those classes:
This one is supposed to create many threads including the WebSocketServer
from websockethread import WebSocketThread
class startManyThreads:
def __init__(self):
self.thread1 = WebSocketThread()
self.thread1.start()
if __name__ == "__main__":
startManyThreads = startManyThreads()
This class should run as my thread:
import threading
from SimpleWebSocketServer import SimpleWebSocketServer
from webSocketServer import WebSocketServer
class WebSocketThread(threading.Thread):
def __init__(self):
threading.Thread.__init__(self)
server = SimpleWebSocketServer('', 8000, WebSocketServer)
server.serveforever()
And this is the "customized" echo example:
from SimpleWebSocketServer import SimpleWebSocketServer, WebSocket
class SimpleEcho(WebSocket):
def handleMessage(self):
# echo message back to client
self.sendMessage(self.data)
def handleConnected(self):
print self.address, 'connected'
def handleClose(self):
print self.address, 'closed'
I have also tried to derive this: class SimpleEcho(WebSocket, threading.Thread):
Any Ideas what i'm doing wrong?
&
Thanks alot in advance!
Edit:
The result when i run "simpleEcho" is that i get a prompt can connect via the websocket.html (provided on github), send and receive Messages
The result when i put it in a thread (anyone of the 3 ways i tried) is the same behaviour except when i try to "connect" from the websocket.html i get a "error: undefined". With nmap i checked and the Server seems so be running & listening to port 8000
Edit 2: Derived new Class from SimpleWebSocketServer
import threading
from SimpleWebSocketServer import SimpleWebSocketServer
class ThreadSimpleWebSocketThread(threading.Thread, SimpleWebSocketServer):
def __init__(self, serversocket):
threading.Thread.__init__(self)
self.serversocket = serversocket
def serveforever(self):
SimpleWebSocketServer.serversocket = self.serversocket
SimpleWebSocketServer.selectInterval = 0.1
SimpleWebSocketServer.listeners = [self.serversocket]
super(ThreadSimpleWebSocketThread, self).serveforever()
def run(self):
self.serveforever()

The main problem seems to be where you're starting the server. The Thread.__init__() method runs inside the main thread (of the caller), not the actual WebSocketThread(). This needs to be done in the Thread.run() method:
class WebSocketThread(threading.Thread):
def __init__(self):
threading.Thread.__init__(self)
def run(self):
server = SimpleWebSocketServer('', 8000, WebSocketServer)
server.serveforever()
The code inside run() actually runs inside the thread.
Note that because of the Global Interpreter Lock, threads won't improve performance much, and you'll probably need multiprocessing. However, if you just want to offload the I/O waiting, this should work fine.
Edit: From looking at this GitHub project, and rethinking what you're trying to do, this isn't trivial. You'll have to override WebSocket.serveforever() in your SimpleEcho() class and change it to accept the socket and pass the accepted socket to a Thread (see here).

Socketserver multiprocessing.Process is starting without calling start()

I have a problem with a Python script on my rpi. If I create a process object, it starts automatically and blocks everything else. I want it to run in the background, and to be able to start it by calling the start() method.
network_manager.py:
import socketserver
class NetworkManagerHandler(socketserver.StreamRequestHandler):
def handle(self):
print("Got some Data!")
class NetworkManagerServer(socketserver.ForkingMixIn, socketserver.TCPServer):
pass
core.py:
import multiprocessing
from network_manager import NetworkManagerServer, NetworkManagerHandler
HOST, PORT = "100.0.0.1", 11891
network_manager = NetworkManagerServer((HOST, PORT), NetworkManagerHandler)
network_manager_process =
multiprocessing.Process(target=network_manager.serve_forever())
# !-> Program is blocking here, but the Server is working. <-!
network_manager_process.daemon = True
network_manager_process.start()
print("Networkmanager is running. (%s:%s)" % (HOST, PORT))
# network_manager.shutdown()
Thanks.

This:
network_manager_process =
multiprocessing.Process(target=network_manager.serve_forever())
Should be this:
network_manager_process =
multiprocessing.Process(target=network_manager.serve_forever)
You don't actually want to call serve_forever, you just want to pass the function to the Process object.

How to call a method from an already running python script

I need to check if the python script is already running then calling a method from the same running python script. But it must be on same process(pid), no new process. Is this possible?
I tried some codes but not worked.
#!/usr/bin/env python
# -*- coding: utf-8 -*-
import Tkinter as tk
from Tkinter import *
import socket
class Main():
def mainFunc(self):
self.root = tk.Tk()
self.root.title("Main Window")
self.lbl = Label(self.root, text = "First Text")
self.lbl.pack()
openStngs = Button(self.root, text = "Open Settings", command=self.settingsFunc)
openStngs.pack()
def settingsFunc(self):
stngsRoot = Toplevel()
stngsRoot.title("Settings Window")
changeTextOfLabel = Button(stngsRoot, text = "Change Main Window Text", command=self.change_text)
changeTextOfLabel.pack()
def change_text(self):
self.lbl.config(text="Text changed")
# the get_lock from http://stackoverflow.com/a/7758075/3254912
def get_lock(process_name):
lock_socket = socket.socket(socket.AF_UNIX, socket.SOCK_DGRAM)
try:
print lock_socket
lock_socket.bind('\0' + process_name)
print 'I got the lock'
m.mainFunc()
mainloop()
except socket.error:
print 'lock exists'
m.settingsFunc()
mainloop()
# sys.exit()
if __name__ == '__main__':
m=Main()
get_lock('myPython.py')

You either need:
A proactive check in your running process to look at the environment (for instance, the contents of a file or data coming through a socket) to know when to fire the function,
or for your running process to receive unix signals or some other IPC (possibly one of the user-defined signals) and perform a function when one is received.
Either way you can't just reach into a running process and fire a function inside that process (it MIGHT not be literally impossible if you hook the running process up to a debugger, but I wouldn't recommend it).
Tkinter necessarily has its own event loop system, so I recommend reading up on how that works and how to either run something on a timer in that event loop system, or set up a callback that responds to a signal. You could also wrap a non-event loop based system in a try/except block that will catch an exception generated by a UNIX signal, but it may not be straightforward to resume the operation of the rest of the program after that signal is caught, in that case.

Sockets are a good solution to this kind of interprocess communication problem.
One possible approach would be to set up a socket server in a thread in your original process, this can be used as an entry point for external input. A (rather stupid) example might be:
# main.py
import socket
import SocketServer # socketserver in Python 3+
import time
from Queue import Queue
from threading import Thread
# class for handling requests
class QueueHandler(SocketServer.BaseRequestHandler):
def __init__(self, request, client_address, server):
self.server = server
server.client_address = client_address
SocketServer.BaseRequestHandler.__init__(self,request, client_address, server)
# receive a block of data
# put it in a Queue instance
# send back the block of data (redundant)
def handle(self):
data = self.request.recv(4096)
self.server.recv_q.put(data)
self.request.send(data)
class TCPServer(SocketServer.TCPServer):
def __init__(self, ip, port, handler_class=QueueHandler):
SocketServer.TCPServer.__init__(self, (ip, port), handler_class, bind_and_activate=False)
self.recv_q = Queue() # a Queue for data received over the socket
self.socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
self.server_bind()
self.server_activate()
def shutdown(self):
SocketServer.TCPServer.shutdown(self)
def __del__(self):
self.server_close()
# This is the equivalent of the main body of your original code
class TheClassThatLovesToAdd(object):
def __init__(self):
self.value = 1
# create and instance of the server attached to some port
self.server = TCPServer("localhost",9999)
# start it listening in a separate control thread
self.server_thread = Thread(target=self.server.serve_forever)
self.server_thread.start()
self.stop = False
def add_one_to_value(self):
self.value += 1
def run(self):
while not self.stop:
print "Value =",self.value
# if there is stuff in the queue...
while not self.server.recv_q.empty():
# read and parse the message from the queue
msg = self.server.recv_q.get()
# perform some action based on the message
if msg == "add":
self.add_one_to_value()
elif msg == "shutdown":
self.server.shutdown()
self.stop = True
time.sleep(1)
if __name__ == "__main__":
x = TheClassThatLovesToAdd()
x.run()
When you start this running, it should just loop over and over printing to the screen. Output:
Value = 1
Value = 1
Value = 1
...
However the TCPServer instance attached to the TheClassThatLovesToAdd instance now gives us a control path. The simplest looking snippet of control code would be:
# control.py
import socket
import sys
sock = socket.socket(socket.AF_INET,socket.SOCK_STREAM)
sock.settimeout(2)
sock.connect(('localhost',9999))
# send some command line argument through the socket
sock.send(sys.argv[1])
sock.close()
So if I run main.py in one terminal window and call python control.py add from another, the output of main.py will change:
Value = 1
Value = 1
Value = 1
Value = 2
Value = 2
...
Finally to kill it all we can run python control.py shutdown, which will gently bring main.py to a halt.
This is by no means the only solution to your problem, but it is likely to be one of the simplest.

One can try GDB, but not sure how to call a function from within [an idle thread].
Perhaps someone very versed with gdb and debugging/calling Python functions from within GDB can improve this answer.

One solution would be to use a messaging service (such as ActiveMQ or RabbitMQ). Your application subscribes to a queue/topic and whenever you want to send it a command, you write a message to it's queue. I'm not going to go into details because there are thousands of examples on-line. Queues/messaging/MQTT etc. are very simple to implement and are how most business systems (and modern control systems) communicate. Do a search for paho-mqtt.