RuntimeError: There is no current event loop in thread … DiscordPy MultiThreading

Question

so I have a python script where I want to run multiple discord bots at the same time. These are defined by how many users there are in the database (Firebase). What I now do is that I have an loop for every user in the database it add's it to an array. Then for every user in that array it starts a script:

def main(user):

        client = discord.Client()

        token = db.child("users").child(user).child("token").get().val()
        print(user + ": " + token)

        applicationId = db.child("users").child(user).child("appid").get().val()

        discordId = user

        @client.event
        async def on_ready():
                print('Online')

        @client.event
        async def on_message(message):
                print(message)
        client.start(token, bot=False)

def testFunction(some_args):
        print(some_args)
        discord_thread = threading.Thread(target=main, args=(some_args,))
        discord_thread.start()

for user in usersArray:
        testFunction(user)

When I start the script it works until the client.start part. Then I get an error for every thread. Error:

Exception in thread Thread-2:
Traceback (most recent call last):
  File "C:\Users\jonah\AppData\Local\Programs\Python\Python37\lib\threading.py", line 926, in _bootstrap_inner
    self.run()
  File "C:\Users\jonah\AppData\Local\Programs\Python\Python37\lib\threading.py", line 870, in run
    self._target(*self._args, **self._kwargs)
  File "discordnotify.py", line 39, in main
    client = discord.Client()
  File "C:\Users\jonah\AppData\Local\Programs\Python\Python37\lib\site-packages\discord\client.py", line 206, in __init__
    self.loop = asyncio.get_event_loop() if loop is None else loop
  File "C:\Users\jonah\AppData\Local\Programs\Python\Python37\lib\asyncio\events.py", line 644, in get_event_loop
    % threading.current_thread().name)
RuntimeError: There is no current event loop in thread 'Thread-2'.

Is there anyone who can maybe help me somehow? It's driving me crazy!

Answer 1

You don't want to use threading when running multiple discord bots. You can view here for some more info, but I can lay it out for you right now. Fixing how you start your discord bots will help you a ton.

For starters, you have to realise that Client.run is an abstraction of a couple of more lower level concepts.

There is Client.login which logs in the client and then Client.connect which actually runs the processing. These are coroutines.

asyncio provides the capability of putting things in the event loop for it to work whenever it has time to.

Something like this eg

loop = asyncio.get_event_loop()

async def foo():
  await asyncio.sleep(10)
  loop.close()

loop.create_task(foo())
loop.run_forever()

If we want to wait for something to happen from another coroutine, asyncio provides us with this functionality as well through the means of synchronisation via asyncio.Event. You can consider this as a boolean that you are waiting for:

e = asyncio.Event()
loop = asyncio.get_event_loop()

async def foo():
  await e.wait()
  print('we are done waiting...')
  loop.stop()

async def bar():
  await asyncio.sleep(20)
  e.set()

loop.create_task(bar())
loop.create_task(foo())
loop.run_forever() # foo will stop this event loop when 'e' is set to true
loop.close()

Using this concept we can apply it to the discord bots themselves.

import asyncio
import discord
from collections import namedtuple

# First, we must attach an event signalling when the bot has been
# closed to the client itself so we know when to fully close the event loop.

Entry = namedtuple('Entry', 'client event')
entries = [
  Entry(client=discord.Client(), event=asyncio.Event()),
  Entry(client=discord.Client(), event=asyncio.Event())
]

# Then, we should login to all our clients and wrap the connect call
# so it knows when to do the actual full closure

loop = asyncio.get_event_loop()

async def login():
  for e in entries:
    await e.client.login()

async def wrapped_connect(entry):
  try:
    await entry.client.connect()
  except Exception as e:
    await entry.client.close()
    print('We got an exception: ', e.__class__.__name__, e)
    entry.event.set()

# actually check if we should close the event loop:
async def check_close():
  futures = [e.event.wait() for e in entries]
  await asyncio.wait(futures)

# here is when we actually login
loop.run_until_complete(login())

# now we connect to every client
for entry in entries:
  loop.create_task(wrapped_connect(entry))

# now we're waiting for all the clients to close
loop.run_until_complete(check_close())

# finally, we close the event loop
loop.close()