python - 异步队列消费者协程

Question

我有一个 asyncio.Protocol 子类从服务器接收数据。我将此数据(每一行，因为数据是文本)存储在 asyncio.Queue 中。

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()

我想有另一个协程负责消费队列中的数据并进行处理。

• 这应该是一个asyncio.Task吗？
• 如果队列因为几秒钟没有收到数据而变空怎么办？如何确保我的消费者不会停止 (run_until_complete)？
• 有没有比为我的队列使用全局变量更简洁的方法？

Answer 1

Should this be a asyncio.Task?

是的，使用 asyncio.ensure_future 创建它或 loop.create_task .

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

只需使用 queue.get等待一个项目可用:

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

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

是的，只需将它作为参数传递给消费者协程和流协议(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()

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

连接关闭后，使用queue.join等待队列为空。

---

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 streams :

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()