如何在asyncio应用中正确使用Python zeroconf？

在asyncio应用中使用zeroconf时，原代码里的同步回调函数调用zeroconf.get_service_info()触发了以下错误：

RuntimeError: Use AsyncServiceInfo.async_request from the event loop

原代码示例：

import asyncio
from zeroconf import Zeroconf, ServiceStateChange
from zeroconf.asyncio import AsyncServiceBrowser

def on_service_state_change(zeroconf, service_type, name, state_change):
    if state_change == ServiceStateChange.Added:
        info = zeroconf.get_service_info(service_type, name)
        print(info)

async def browse_services():
    zeroconf = Zeroconf()
    service_type = "_http._tcp.local."

    browser = AsyncServiceBrowser(zeroconf, service_type, handlers=[on_service_state_change])

    try:
        await asyncio.Event().wait()
    finally:
        zeroconf.close()

if __name__ == "__main__":
    asyncio.run(browse_services())

正确实现方式 #

核心问题是异步环境下不能使用zeroconf的同步API，同时回调函数需要适配异步逻辑。修正后的实现如下：

1. 使用AsyncZeroconf替代同步的Zeroconf，适配asyncio事件循环
2. 将回调函数改为异步函数，内部使用异步API获取服务信息
3. 借助async with自动管理AsyncZeroconf的资源释放

完整修正代码：

import asyncio
from zeroconf import ServiceStateChange
from zeroconf.asyncio import AsyncServiceBrowser, AsyncZeroconf

async def handle_service_change(zeroconf: AsyncZeroconf, service_type, name, state_change):
    if state_change == ServiceStateChange.Added:
        # 使用异步API获取服务信息
        info = await zeroconf.async_get_service_info(service_type, name)
        print(f"发现服务：{info}")

async def browse_services():
    # 用AsyncZeroconf替代同步Zeroconf，配合async with自动释放资源
    async with AsyncZeroconf() as zeroconf:
        service_type = "_http._tcp.local."
        # 传入异步回调函数，zeroconf会自动在事件循环中调度执行
        browser = AsyncServiceBrowser(zeroconf, service_type, handlers=[handle_service_change])
        # 保持事件循环持续运行
        await asyncio.Event().wait()

if __name__ == "__main__":
    asyncio.run(browse_services())

关键修改说明 #

• AsyncZeroconf：异步版本的核心实例，提供所有异步操作API，避免同步API在事件循环中引发阻塞或错误
• 异步回调：zeroconf的异步浏览器支持接收异步回调函数，会自动将其包装为asyncio任务调度执行，无需手动调用asyncio.create_task
• 资源管理：async with语法自动处理AsyncZeroconf的初始化和关闭，替代手动调用close()的繁琐操作

内容的提问来源于stack exchange，提问作者Tom