Python10天冲刺《aiohttp》异步任务来实现自动重连

为了实现在 on_close 回调中重新连接的功能，我们可以利用 aiohttp 的 WebSocket 功能，并结合异步任务来实现自动重连。以下是一个示例代码，展示了如何在 on_close 回调中重新连接。

示例代码

import asyncio
import aiohttp
import logging

logging.basicConfig(level=logging.INFO)

async def on_message(message):
    logging.info(f"Received message: {message}")

async def on_close(session, url):
    logging.warning("WebSocket connection closed. Attempting to reconnect.")
    await safe_connect(session, url)

async def safe_connect(session, url, max_retries=5):
    retries = 0
    while True:
        try:
            async with session.ws_connect(url) as ws:
                logging.info("Connected to WebSocket server.")
                async for msg in ws:
                    if msg.type == aiohttp.WSMsgType.TEXT:
                        await on_message(msg.data)
                    elif msg.type == aiohttp.WSMsgType.CLOSED:
                        break
                    elif msg.type == aiohttp.WSMsgType.ERROR:
                        logging.error(f"WebSocket error: {ws.exception()}")
                        break
        except (aiohttp.ClientConnectionError, aiohttp.ServerDisconnectedError, asyncio.TimeoutError) as e:
            retries += 1
            if retries >= max_retries:
                raise Exception(f"Max retries ({max_retries}) exceeded for {url}") from e
            logging.warning(f"Retrying ({retries}/{max_retries}): {e}")
            await asyncio.sleep(2 ** retries)  # Exponential backoff
        finally:
            await on_close(session, url)

async def main():
    url = 'wss://api.example.com/ws'
    async with aiohttp.ClientSession() as session:
        await safe_connect(session, url)

if __name__ == '__main__':
    loop = asyncio.get_event_loop()
    loop.run_until_complete(main())

代码解释

1. 导入必要的模块

   import asyncio
   import aiohttp
   import logging
   
   logging.basicConfig(level=logging.INFO)
   

2. 定义消息处理函数

   async def on_message(message):
       logging.info(f"Received message: {message}")
   

3. 定义连接关闭回调函数

   async def on_close(session, url):
       logging.warning("WebSocket connection closed. Attempting to reconnect.")
       await safe_connect(session, url)
   

4. 定义带有重试逻辑的安全连接函数

   async def safe_connect(session, url, max_retries=5):
       retries = 0
       while True:
           try:
               async with session.ws_connect(url) as ws:
                   logging.info("Connected to WebSocket server.")
                   async for msg in ws:
                       if msg.type == aiohttp.WSMsgType.TEXT:
                           await on_message(msg.data)
                       elif msg.type == aiohttp.WSMsgType.CLOSED:
                           break
                       elif msg.type == aiohttp.WSMsgType.ERROR:
                           logging.error(f"WebSocket error: {ws.exception()}")
                           break
           except (aiohttp.ClientConnectionError, aiohttp.ServerDisconnectedError, asyncio.TimeoutError) as e:
               retries += 1
               if retries >= max_retries:
                   raise Exception(f"Max retries ({max_retries}) exceeded for {url}") from e
               logging.warning(f"Retrying ({retries}/{max_retries}): {e}")
               await asyncio.sleep(2 ** retries)  # Exponential backoff
           finally:
               await on_close(session, url)
   

5. 定义主函数

   async def main():
       url = 'wss://api.example.com/ws'
       async with aiohttp.ClientSession() as session:
           await safe_connect(session, url)
   

6. 启动事件循环

   if __name__ == '__main__':
       loop = asyncio.get_event_loop()
       loop.run_until_complete(main())
   

注意事项

• 指数退避策略: 在每次重试之间增加等待时间，以减少对服务器的压力。
• 最大重试次数: 防止无限重试导致程序挂起。
• 日志记录: 记录重试和失败的信息，便于调试和监控。

通过这种方式，可以在 on_close 回调中重新连接 WebSocket 连接，从而实现更可靠的通信。希望这对您有所帮助！如果有任何进一步的问题，请随时提问。