Question

我正在研究在具有4G内存的Ubuntu机器上运行的Python应用程序的问题。该工具将用于审核服务器（我们更喜欢使用自己的工具）。它使用线程连接到许多服务器，并且许多TCP连接失败。但是，如果我在开始每个线程之间添加1秒的延迟，那么大多数连接都会成功。我使用这个简单的脚本来调查可能发生的事情：

#!/usr/bin/python

import sys
import socket
import threading
import time

class Scanner(threading.Thread):
    def __init__(self, host, port):
        threading.Thread.__init__(self)
        self.host = host
        self.port = port
        self.status = ""

    def run(self):
        self.sk = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        self.sk.settimeout(20)
        try:
            self.sk.connect((self.host, self.port))
        except Exception, err:
            self.status = str(err)
        else:
            self.status = "connected"
        finally:
            self.sk.close()


def get_hostnames_list(filename):
    return open(filename).read().splitlines()

if (__name__ == "__main__"):
    hostnames_file = sys.argv[1]
    hosts_list = get_hostnames_list(hostnames_file)
    threads = []
    for host in hosts_list:
        #time.sleep(1)
        thread = Scanner(host, 443)
        threads.append(thread)
        thread.start()

    for thread in threads:
        thread.join()
        print "Host: ", thread.host, " : ", thread.status

如果我在time.sleep（1）注释掉的情况下执行此操作，比方说，300个主机中的许多连接都会因超时错误而失败，而如果我将延迟时间设置为1秒，它们就不会超时。是否在另一台运行在功能更强大的机器上的Linux发行版上试用了应用程序并且没有那么多的连接错误？是由于内核限制吗？有没有什么可以让连接工作而不会延迟？

更新

我还尝试过一个限制池中可用线程数的程序。通过将其减少到20，我可以使所有连接工作，但它只检查大约1个主机每秒。所以无论我尝试什么（放入睡眠（1）或限制并发线程的数量），我似乎无法每秒检查多于1个主机。

更新

我刚刚发现 question ，这与我所看到的相似。

更新

我想知道用扭曲写这个可能会有帮助吗？任何人都可以展示我的例子看起来像使用twisted写的吗？

Answer 1

您可以尝试gevent：

from gevent.pool import Pool    
from gevent import monkey; monkey.patch_all() # patches stdlib    
import sys
import logging    
from httplib import HTTPSConnection
from timeit import default_timer as timer    
info = logging.getLogger().info

def connect(hostname):
    info("connecting %s", hostname)
    h = HTTPSConnection(hostname, timeout=2)
    try: h.connect()
    except IOError, e:
        info("error %s reason: %s", hostname, e)
    else:
        info("done %s", hostname)
    finally:
        h.close()

def main():
    logging.basicConfig(level=logging.INFO, format="%(asctime)s %(message)s")    
    info("getting hostname list")
    hosts_file = sys.argv[1] if len(sys.argv) > 1 else "hosts.txt"
    hosts_list = open(hosts_file).read().splitlines()    
    info("spawning jobs")
    pool = Pool(20) # limit number of concurrent connections
    start = timer()
    for _ in pool.imap(connect, hosts_list):
        pass
    info("%d hosts took us %.2g seconds", len(hosts_list), timer() - start)

if __name__=="__main__":
    main()

它每秒可以处理多个主机。

输出

2011-01-31 11:08:29,052 getting hostname list
2011-01-31 11:08:29,052 spawning jobs
2011-01-31 11:08:29,053 connecting www.yahoo.com
2011-01-31 11:08:29,053 connecting www.abc.com
2011-01-31 11:08:29,053 connecting www.google.com
2011-01-31 11:08:29,053 connecting stackoverflow.com
2011-01-31 11:08:29,053 connecting facebook.com
2011-01-31 11:08:29,054 connecting youtube.com
2011-01-31 11:08:29,054 connecting live.com
2011-01-31 11:08:29,054 connecting baidu.com
2011-01-31 11:08:29,054 connecting wikipedia.org
2011-01-31 11:08:29,054 connecting blogspot.com
2011-01-31 11:08:29,054 connecting qq.com
2011-01-31 11:08:29,055 connecting twitter.com
2011-01-31 11:08:29,055 connecting msn.com
2011-01-31 11:08:29,055 connecting yahoo.co.jp
2011-01-31 11:08:29,055 connecting taobao.com
2011-01-31 11:08:29,055 connecting google.co.in
2011-01-31 11:08:29,056 connecting sina.com.cn
2011-01-31 11:08:29,056 connecting amazon.com
2011-01-31 11:08:29,056 connecting google.de
2011-01-31 11:08:29,056 connecting google.com.hk
2011-01-31 11:08:29,188 done www.google.com
2011-01-31 11:08:29,189 done google.com.hk
2011-01-31 11:08:29,224 error wikipedia.org reason: [Errno 111] Connection refused
2011-01-31 11:08:29,225 done google.co.in
2011-01-31 11:08:29,227 error msn.com reason: [Errno 111] Connection refused
2011-01-31 11:08:29,228 error live.com reason: [Errno 111] Connection refused
2011-01-31 11:08:29,250 done google.de
2011-01-31 11:08:29,262 done blogspot.com
2011-01-31 11:08:29,271 error www.abc.com reason: [Errno 111] Connection refused
2011-01-31 11:08:29,465 done amazon.com
2011-01-31 11:08:29,467 error sina.com.cn reason: [Errno 111] Connection refused
2011-01-31 11:08:29,496 done www.yahoo.com
2011-01-31 11:08:29,521 done stackoverflow.com
2011-01-31 11:08:29,606 done youtube.com
2011-01-31 11:08:29,939 done twitter.com
2011-01-31 11:08:33,056 error qq.com reason: timed out
2011-01-31 11:08:33,057 error taobao.com reason: timed out
2011-01-31 11:08:33,057 error yahoo.co.jp reason: timed out
2011-01-31 11:08:34,466 done facebook.com
2011-01-31 11:08:35,056 error baidu.com reason: timed out
2011-01-31 11:08:35,057 20 hosts took us 6 seconds

Answer 2

我想知道用扭曲写这个可能会有帮助吗？任何人都可以展示我的例子看起来像使用twisted写的吗？

此变体比the code that uses gevent快得多：

#!/usr/bin/env python
import sys
from timeit import default_timer as timer

from twisted.internet import defer, protocol, reactor, ssl, task
from twisted.python   import log

info = log.msg

class NoopProtocol(protocol.Protocol):
    def makeConnection(self, transport):
        transport.loseConnection()

def connect(host, port, contextFactory=ssl.ClientContextFactory(), timeout=30):
    info("connecting %s" % host)
    cc = protocol.ClientCreator(reactor, NoopProtocol)
    d = cc.connectSSL(host, port, contextFactory, timeout)
    d.addCallbacks(lambda _: info("done %s" % host),
                   lambda f: info("error %s reason: %s" % (host, f.value)))
    return d

def n_at_a_time(it, n):
    """Iterate over `it` concurently `n` items at a time.

    `it` - an iterator creating Deferreds
    `n`  - number of concurrent iterations
    return a deferred that fires on completion
    """
    return defer.DeferredList([task.coiterate(it) for _ in xrange(n)])

def main():
    try:
        log.startLogging(sys.stderr, setStdout=False)

        info("getting hostname list")
        hosts_file = sys.argv[1] if len(sys.argv) > 1 else "hosts.txt"
        hosts_list = open(hosts_file).read().splitlines()

        info("spawning jobs")
        start = timer()        
        jobs = (connect(host, 443, timeout=2) for host in hosts_list)
        d = n_at_a_time(jobs, n=20) # limit number of simultaneous connections
        d.addCallback(lambda _: info("%d hosts took us %.2g seconds" % (
            len(hosts_list), timer() - start)))
        d.addBoth(lambda _: (info("the end"), reactor.stop()))
    except:
        log.err()
        reactor.stop()

if __name__=="__main__":
    reactor.callWhenRunning(main)
    reactor.run()

以下是使用t.i.d.inlineCallbacks的变体。它需要Python 2.5或更高版本。它允许以同步（阻塞）方式编写异步代码：

#!/usr/bin/env python
import sys
from timeit import default_timer as timer

from twisted.internet import defer, protocol, reactor, ssl, task
from twisted.python   import log

info = log.msg

class NoopProtocol(protocol.Protocol):
    def makeConnection(self, transport):
        transport.loseConnection()

@defer.inlineCallbacks
def connect(host, port, contextFactory=ssl.ClientContextFactory(), timeout=30):
    info("connecting %s" % host)
    cc = protocol.ClientCreator(reactor, NoopProtocol)
    try:
        yield cc.connectSSL(host, port, contextFactory, timeout)
    except Exception, e:
        info("error %s reason: %s" % (host, e))
    else:
        info("done %s" % host)

def n_at_a_time(it, n):
    """Iterate over `it` concurently `n` items at a time.

    `it` - an iterator creating Deferreds
    `n`  - number of concurrent iterations
    return a deferred that fires on completion
    """
    return defer.DeferredList([task.coiterate(it) for _ in xrange(n)])

@defer.inlineCallbacks
def main():
    try:
        log.startLogging(sys.stderr, setStdout=False)

        info("getting hostname list")
        hosts_file = sys.argv[1] if len(sys.argv) > 1 else "hosts.txt"
        hosts_list = open(hosts_file).read().splitlines()

        info("spawning jobs")
        start = timer()        
        jobs = (connect(host, 443, timeout=2) for host in hosts_list)
        yield n_at_a_time(jobs, n=20) # limit number of simultaneous connections
        info("%d hosts took us %.2g seconds" % (len(hosts_list), timer()-start))
        info("the end")
    except:
        log.err()
    finally:
        reactor.stop()

if __name__=="__main__":
    reactor.callWhenRunning(main)
    reactor.run()

Answer 3

真正的线程池怎么样？

#!/usr/bin/env python3

# http://code.activestate.com/recipes/577187-python-thread-pool/

from queue import Queue
from threading import Thread

class Worker(Thread):
    def __init__(self, tasks):
        Thread.__init__(self)
        self.tasks = tasks
        self.daemon = True
        self.start()

    def run(self):
        while True:
            func, args, kargs = self.tasks.get()
            try: func(*args, **kargs)
            except Exception as exception: print(exception)
            self.tasks.task_done()

class ThreadPool:
    def __init__(self, num_threads):
        self.tasks = Queue(num_threads)
        for _ in range(num_threads): Worker(self.tasks)

    def add_task(self, func, *args, **kargs):
        self.tasks.put((func, args, kargs))

    def wait_completion(self):
        self.tasks.join()

示例：

import threadpool
pool = threadpool.ThreadPool(20) # 20 threads
pool.add_task(print, "test")
pool.wait_completion()

它在python 3中，但不应该太难转换为2.x.如果这可以解决您的问题，我并不感到惊讶。

Answer 4

Python 3.4为异步IO引入了新的provisional API - asyncio module。

此方法类似于twisted-based answer：

#!/usr/bin/env python3.4
import asyncio
import logging
from contextlib import closing

class NoopProtocol(asyncio.Protocol):
    def connection_made(self, transport):
        transport.close()

info = logging.getLogger().info

@asyncio.coroutine
def connect(loop, semaphor, host, port=443, ssl=True, timeout=15):
    try:
        with (yield from semaphor):
            info("connecting %s" % host)
            done, pending = yield from asyncio.wait(
                [loop.create_connection(NoopProtocol, host, port, ssl=ssl)],
                loop=loop, timeout=timeout)
            if done:
                next(iter(done)).result()
    except Exception as e:
        info("error %s reason: %s" % (host, e))
    else:
        if pending:
            info("error %s reason: timeout" % (host,))
            for ft in pending:
                ft.cancel()
        else:
            info("done %s" % host)

@asyncio.coroutine
def main(loop):
    logging.basicConfig(level=logging.INFO, format="%(asctime)s %(message)s")
    limit, timeout, hosts = parse_cmdline()

    # connect `limit` concurrent connections
    sem = asyncio.BoundedSemaphore(limit)
    coros = [connect(loop, sem, host, timeout=timeout) for host in hosts]
    if coros:
        yield from asyncio.wait(coros, loop=loop)

if __name__=="__main__":
    with closing(asyncio.get_event_loop()) as loop:
        loop.run_until_complete(main(loop))

除了twisted变体之外，它还使用NoopProtocol除了在成功连接时立即断开连接之外什么都不做。

使用信号量限制并发连接数。

代码为coroutine-based。

实施例

要了解我们可以从前百万Alexa列表中向前1000个主机建立多少个成功的ssl连接：

$ curl -O http://s3.amazonaws.com/alexa-static/top-1m.csv.zip
$ unzip *.zip
$ /usr/bin/time perl -nE'say $1 if /\d+,([^\s,]+)$/' top-1m.csv | head -1000 |\
    python3.4 asyncio_ssl.py - --timeout 60 |& tee asyncio.log

结果是所有连接中只有不到一半成功。平均而言，它每秒检查约20台主机。许多网站在一分钟后超时。如果主机与服务器证书中的主机名不匹配，则连接也会失败。它包括example.com与www.example.com类比较。

Answer 5

首先，尝试使用非阻塞套接字。另一个原因是你正在消耗所有短暂的端口。尝试删除限制。

多线程Python应用程序和套接字连接的问题

5 个答案:

输出

实施例