Python Flask，如何检测SSE客户端与前端Java脚本断开连接 [英] Python Flask, how to detect a SSE client disconnect from front end Javascript

问题描述

也许这是Flask中的问题，无法在服务器端处理断开连接事件.

Maybe this is a problem in Flask, there is no way to handle disconnection event on the server side.

在Response类中，有一个名为"call_on_close"的方法，我们可以在其中添加不带参数的函数，例如on_close()，将在调用响应对象的close方法时将其触发，但是当我从Javascript的客户端调用EventSource.close()时，不会发生这种情况.

In Response class, there is a method named "call_on_close", where we can add a function without argument, e.g. on_close(), it will be fired when the response object's close method called, but this doesn't happen when I call EventSource.close() from the client side in Javascript.

服务器端代码:

from flask import Response
r = Response(stream(), ...)
r.call_on_close(on_close)
return r 

def on_close():
  print "response is closed!"

def stream():
  ...  # subscribe to redis
  for message in pubsub.listen():
    ....
    yield 'data: %s\n\n' % message

在客户端:将卸载处理程序添加到具有SSE的页面

on client side: add unload handler to page with SSE

$(window).unload(
  function() {
    sse.close();
  }
}

有什么问题吗?

任何建议或带有代码的解决方案都将受到赞赏！

Any suggestions or solution with code is appreciated!

提前谢谢！

推荐答案

生成器收到GeneratorExit异常，并且在该时间您将知道它将退出.例如:

The generator receives a GeneratorExit exception, and that's when you know it will exit. For example:

def stream():
    try:
        i = 0
        while True:
            yield 'Hello {}!'.format(i)
            i += 1
            time.sleep(1)
    finally:
        # Called after a GeneratorExit, cleanup here
        i = 0


@app.route('/messages')
def messages():
    return Response(stream(), content_type='text/event-stream')

将产生无限的"Hello!"流，您将知道完成后在哪里可以运行清除代码.如果您的生成器阻塞了线程，则需要以某种方式(可能是推动虚拟项)将其解除阻塞，以便可以关闭生成器.

Will yield a infinite stream of "Hello!", and you will know when it's done, where you can run cleanup code. If your generator blocks the thread, it will need to be unblocked in some way (maybe pushing a dummy item) so that the generator can be closed.

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