在单独的线程中执行 run_coroutine_threadsafe

2022-01-15 00:00:00 python python-asyncio async-await discord.py

问题描述

我有一个永远运行的脚本(它检查文件的变化).每当制作奇怪的文件时，我都需要发送 Discord 消息.

I have a script that is constantly running forever (it checks changes in files). I need to send Discord messages whenever a weird file is made.

  • 问题是，事件监听函数(下面的def run(self):)来自一个子类，所以我不能把它改成async def run(self):.因此我不能使用 await channel.send()
  • 我对此的解决方案是使用 run_coroutine_threadsafe，如下所述:https://stackoverflow.com/一个/53726266/9283107.效果很好！但问题是，消息被放入队列中，并且在此脚本完成之前它们永远不会被发送(在我的情况下是:永远不会).我假设发送消息函数被放入该脚本所在的线程中，因此线程永远不会到达它们?
  • Problem is, the event watching function (def run(self): below) is from a subclass, so I can't change it to async def run(self):. Therefore I can't use await channel.send()
  • My solution to this was to use run_coroutine_threadsafe like explained here: https://stackoverflow.com/a/53726266/9283107. That works good! But the problem is, the messages get put into a queue and they never get sent until this script finishes (which in my case would be: never). I assume the send message functions get put into the thread that this script is on, therefore the thread never gets to them?

也许我们可以将 run_coroutine_threadsafe 扔到一个单独的线程中或什么的?这是我能做的最小的例子，它仍然显示了我的子类问题.

Maybe we can throw the run_coroutine_threadsafe into a separate thread or something? This is the most minimal example I can make that still shows my subclass problem.

import discord
import os
import asyncio
import time

# CHANNEL_ID = 7659170174????????
client = discord.Client()
channel = None

class Example():
    # Imagine this run comes from a subclass, so you can't add sync to it!
    def run(self):
        # await channel.send('Test') # We can't do this because of the above comment
        asyncio.run_coroutine_threadsafe(channel.send('Test'), _loop)
        print('Message sent')

@client.event
async def on_ready():
    print('Discord ready')
    global channel
    channel = client.get_channel(CHANNEL_ID)

    for i in range(2):
        Example().run()
        time.sleep(3)

    print('Discord messages should appear by now. Sleeping for 20s to give it time (technically this would be infinite)')
    time.sleep(20)
    print('Script done. Now they only get sent for some reason')

_loop = asyncio.get_event_loop()

client.run('Your secret token')

解决方案

首先，请注意，您不能从 async 调用阻塞代码，例如 time.sleep()定义.要启动一个阻塞函数并让它与 asyncio 通信，您可以从 on_ready 甚至从顶层生成一个后台线程，如下所示:

First, note that you're not allowed to call blocking code such as time.sleep() from an async def. To start a blocking function and have it communicate with asyncio, you can spawn a background thread from on_ready or even from top-level, like this:

# checker_function is the function that blocks and that
# will invoke Example.run() in a loop.
threading.Thread(
    target=checker_function,
    args=(asyncio.get_event_loop(), channel)
).start()

您的主线程将运行 asyncio 事件循环，而您的后台线程将检查文件，使用 asyncio.run_coroutine_threadsafe() 与 asyncio 和 discord 进行通信.

Your main thread will run the asyncio event loop and your background thread will check the files, using asyncio.run_coroutine_threadsafe() to communicate with asyncio and discord.

正如您链接到的答案下的评论中指出的那样，asyncio.run_coroutine_threadsafe 假定您有多个线程正在运行(因此是线程安全的")，其中一个运行事件循环.在您实现之前，任何使用 asyncio.run_coroutine_threadsafe 的尝试都会失败.

As pointed out in a comment under the answer you linked to, asyncio.run_coroutine_threadsafe assumes that you have multiple threads running (hence "thread-safe"), one of which runs the event loop. Until you implement that, any attempt to use asyncio.run_coroutine_threadsafe will fail.

相关文章