我将如何在实时场景中使用并发。期货和队列？

Question

concurrent.futures如下所示，使用Python 3的模块进行并行工作非常容易。

with concurrent.futures.ThreadPoolExecutor(max_workers=10) as executor:
    future_to = {executor.submit(do_work, input, 60): input for input in dictionary}
    for future in concurrent.futures.as_completed(future_to):
        data = future.result()

将项目插入和检索到队列中也非常方便。

q = queue.Queue()
for task in tasks:
q.put(task)
while not q.empty():
   q.get()

我有一个脚本在后台运行，以监听更新。现在，理论上假设，随着这些更新的到来，我将对它们进行排队，并使用进行并发处理ThreadPoolExecutor。

现在，单独地，所有这些组件都是独立工作的，并且很有意义，但是我如何一起使用它们呢？我不知道是否有可能ThreadPoolExecutor实时从队列中馈送工作，除非预先确定要工作的数据？

简而言之，我要做的就是，每秒接收4条消息的更新，将它们推送到队列中，并让我的current.futures对其进行处理。如果我不这样做，那我就会陷入缓慢的顺序方法中。

让我们以下面的Python文档中的规范示例为例：

with concurrent.futures.ThreadPoolExecutor(max_workers=5) as executor:
    future_to_url = {executor.submit(load_url, url, 60): url for url in URLS}
    for future in concurrent.futures.as_completed(future_to_url):
        url = future_to_url[future]
        try:
            data = future.result()
        except Exception as exc:
            print('%r generated an exception: %s' % (url, exc))
        else:
            print('%r page is %d bytes' % (url, len(data)))

的列表URLS是固定的。是否可以实时提供此列表，并让工作人员从列表中进行处理，也许出于管理目的而从队列中进行处理？我有点困惑我的方法是否 真能 ？

Answer 1

Python文档中的示例已扩展为可以从队列中进行工作。需要注意的更改是，此代码使用concurrent.futures.wait而不是concurrent.futures.as_completed允许在等待其他工作完成时开始新工作。

import concurrent.futures
import urllib.request
import time
import queue

q = queue.Queue()

URLS = ['http://www.foxnews.com/',
        'http://www.cnn.com/',
        'http://europe.wsj.com/',
        'http://www.bbc.co.uk/',
        'http://some-made-up-domain.com/']

def feed_the_workers(spacing):
    """ Simulate outside actors sending in work to do, request each url twice """
    for url in URLS + URLS:
        time.sleep(spacing)
        q.put(url)
    return "DONE FEEDING"

def load_url(url, timeout):
    """ Retrieve a single page and report the URL and contents """
    with urllib.request.urlopen(url, timeout=timeout) as conn:
        return conn.read()

# We can use a with statement to ensure threads are cleaned up promptly
with concurrent.futures.ThreadPoolExecutor(max_workers=5) as executor:

    # start a future for a thread which sends work in through the queue
    future_to_url = {
        executor.submit(feed_the_workers, 0.25): 'FEEDER DONE'}

    while future_to_url:
        # check for status of the futures which are currently working
        done, not_done = concurrent.futures.wait(
            future_to_url, timeout=0.25,
            return_when=concurrent.futures.FIRST_COMPLETED)

        # if there is incoming work, start a new future
        while not q.empty():

            # fetch a url from the queue
            url = q.get()

            # Start the load operation and mark the future with its URL
            future_to_url[executor.submit(load_url, url, 60)] = url

        # process any completed futures
        for future in done:
            url = future_to_url[future]
            try:
                data = future.result()
            except Exception as exc:
                print('%r generated an exception: %s' % (url, exc))
            else:
                if url == 'FEEDER DONE':
                    print(data)
                else:
                    print('%r page is %d bytes' % (url, len(data)))

            # remove the now completed future
            del future_to_url[future]

url两次获取的输出：

'http://www.foxnews.com/' page is 67574 bytes
'http://www.cnn.com/' page is 136975 bytes
'http://www.bbc.co.uk/' page is 193780 bytes
'http://some-made-up-domain.com/' page is 896 bytes
'http://www.foxnews.com/' page is 67574 bytes
'http://www.cnn.com/' page is 136975 bytes
DONE FEEDING
'http://www.bbc.co.uk/' page is 193605 bytes
'http://some-made-up-domain.com/' page is 896 bytes
'http://europe.wsj.com/' page is 874649 bytes
'http://europe.wsj.com/' page is 874649 bytes