异步队列消费者协程 [英] asyncio queue consumer coroutine

问题描述

我有一个 asyncio.Protocol 子类，它从服务器接收数据。
我将此数据（每行，因为数据是文本）存储在 asyncio.Queue 中。

I have a asyncio.Protocol subclass receiving data from a server. I am storing this data (each line, because the data is text) in a asyncio.Queue.

import asyncio

q = asyncio.Queue()

class StreamProtocol(asyncio.Protocol):
    def __init__(self, loop):
        self.loop = loop
        self.transport = None

    def connection_made(self, transport):
        self.transport = transport

    def data_received(self, data):
        for message in data.decode().splitlines():
            yield q.put(message.rstrip())

    def connection_lost(self, exc):
        self.loop.stop()

loop = asyncio.get_event_loop()
coro = loop.create_connection(lambda: StreamProtocol(loop),
                              '127.0.0.1', '42')
loop.run_until_complete(coro)
loop.run_forever()
loop.close()

我想让另一个协程负责消耗队列中的数据，

I want to have another coroutine responsible for consuming the data in the queue and processing it.

• 这应该是 asyncio.Task 吗？


• 如果由于几秒钟没有收到数据而导致队列变空怎么办？我如何确保我的使用者不会停止（ run_until_complete ）？


• 有没有一种比使用全局变量更干净的方法我的队列？

• Should this be a asyncio.Task?
• What if the queue becomes empty because for a few seconds no data is received? How can I make sure my consumer doesn't stop (run_until_complete)?
• Is there a cleaner way than using a global variable for my queue?

推荐答案

这应该是asyncio.Task ？

Should this be a asyncio.Task?

是的，使用 asyncio.ensure_future 或 loop.create_task 。

如果队列由于几秒钟而变空怎么办

What if the queue becomes empty because for a few seconds no data is received?

只需使用 queue.get 等到某个商品可用：

Simply use queue.get to wait until an item is available:

async def consume(queue):
    while True:
        item = await queue.get()
        print(item)

是否有比在队列中使用全局变量更清洁的方法？

Is there a cleaner way than using a global variable for my queue?

是的，只需将其作为参数传递给消费者协程，然后流协议：

Yes, simply pass it as argument to the consumer coroutine and stream protocol:

class StreamProtocol(asyncio.Protocol):
    def __init__(self, loop, queue):
        self.loop = loop
        self.queue = queue

    def data_received(self, data):
        for message in data.decode().splitlines():
            self.queue.put_nowait(message.rstrip())

    def connection_lost(self, exc):
        self.loop.stop()

如何确保我的消费者不会停止（run_until_complete）？

How can I make sure my consumer doesn't stop (run_until_complete)?

一旦关闭连接，请使用 queue.join 到

Once the connection is closed, use queue.join to wait until the queue is empty.

完整示例：

loop = asyncio.get_event_loop()
queue = asyncio.Queue()
# Connection coroutine
factory = lambda: StreamProtocol(loop, queue)
connection = loop.create_connection(factory, '127.0.0.1', '42')
# Consumer task
consumer = asyncio.ensure_future(consume(queue))
# Set up connection
loop.run_until_complete(connection)
# Wait until the connection is closed
loop.run_forever()
# Wait until the queue is empty
loop.run_until_complete(queue.join())
# Cancel the consumer
consumer.cancel()
# Let the consumer terminate
loop.run_until_complete(consumer)
# Close the loop
loop.close()

或者，您也可以使用流：

async def tcp_client(host, port, loop=None):
    reader, writer = await asyncio.open_connection(host, port, loop=loop)
    async for line in reader:
        print(line.rstrip())
    writer.close()

loop = asyncio.get_event_loop()
loop.run_until_complete(tcp_client('127.0.0.1', 42, loop))
loop.close()

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