What is the fastest way to send 100,000 HTTP requests in Python?


I am opening a file which has 100,000 URL’s. I need to send an HTTP request to each URL and print the status code. I am using Python 2.6, and so far looked at the many confusing ways Python implements threading/concurrency. I have even looked at the python concurrence library, but cannot figure out how to write this program correctly. Has anyone come across a similar problem? I guess generally I need to know how to perform thousands of tasks in Python as fast as possible – I suppose that means ‘concurrently’.

Asked By: IgorGanapolsky



The easiest way would be to use Python’s built-in threading library. They’re not “real” / kernel threads They have issues (like serialization), but are good enough. You’d want a queue & thread pool. One option is here, but it’s trivial to write your own. You can’t parallelize all 100,000 calls, but you can fire off 100 (or so) of them at the same time.

Answered By: pestilence669

Using a thread pool is a good option, and will make this fairly easy. Unfortunately, python doesn’t have a standard library that makes thread pools ultra easy. But here is a decent library that should get you started:

Code example from their site:

pool = ThreadPool(poolsize)
requests = makeRequests(some_callable, list_of_args, callback)
[pool.putRequest(req) for req in requests]

Hope this helps.

Answered By: Kevin Wiskia

For your case, threading will probably do the trick as you’ll probably be spending most time waiting for a response. There are helpful modules like Queue in the standard library that might help.

I did a similar thing with parallel downloading of files before and it was good enough for me, but it wasn’t on the scale you are talking about.

If your task was more CPU-bound, you might want to look at the multiprocessing module, which will allow you to utilize more CPUs/cores/threads (more processes that won’t block each other since the locking is per process)

Answered By: Mattias Nilsson

A good approach to solving this problem is to first write the code required to get one result, then incorporate threading code to parallelize the application.

In a perfect world this would simply mean simultaneously starting 100,000 threads which output their results into a dictionary or list for later processing, but in practice you are limited in how many parallel HTTP requests you can issue in this fashion. Locally, you have limits in how many sockets you can open concurrently, how many threads of execution your Python interpreter will allow. Remotely, you may be limited in the number of simultaneous connections if all the requests are against one server, or many. These limitations will probably necessitate that you write the script in such a way as to only poll a small fraction of the URLs at any one time (100, as another poster mentioned, is probably a decent thread pool size, although you may find that you can successfully deploy many more).

You can follow this design pattern to resolve the above issue:

  1. Start a thread which launches new request threads until the number of currently running threads (you can track them via threading.active_count() or by pushing the thread objects into a data structure) is >= your maximum number of simultaneous requests (say 100), then sleeps for a short timeout. This thread should terminate when there is are no more URLs to process. Thus, the thread will keep waking up, launching new threads, and sleeping until your are finished.
  2. Have the request threads store their results in some data structure for later retrieval and output. If the structure you are storing the results in is a list or dict in CPython, you can safely append or insert unique items from your threads without locks, but if you write to a file or require in more complex cross-thread data interaction you should use a mutual exclusion lock to protect this state from corruption.

I would suggest you use the threading module. You can use it to launch and track running threads. Python’s threading support is bare, but the description of your problem suggests that it is completely sufficient for your needs.

Finally, if you’d like to see a pretty straightforward application of a parallel network application written in Python, check out ssh.py. It’s a small library which uses Python threading to parallelize many SSH connections. The design is close enough to your requirements that you may find it to be a good resource.

Answered By: Erik Garrison

If you’re looking to get the best performance possible, you might want to consider using Asynchronous I/O rather than threads. The overhead associated with thousands of OS threads is non-trivial and the context switching within the Python interpreter adds even more on top of it. Threading will certainly get the job done but I suspect that an asynchronous route will provide better overall performance.

Specifically, I’d suggest the async web client in the Twisted library (http://www.twistedmatrix.com). It has an admittedly steep learning curve but it quite easy to use once you get a good handle on Twisted’s style of asynchronous programming.

A HowTo on Twisted’s asynchronous web client API is available at:


Answered By: Rakis

Threads are absolutely not the answer here. They will provide both process and kernel bottlenecks, as well as throughput limits that are not acceptable if the overall goal is “the fastest way”.

A little bit of twisted and its asynchronous HTTP client would give you much better results.

Answered By: ironfroggy

Consider using Windmill , although Windmill probably cant do that many threads.

You could do it with a hand rolled Python script on 5 machines, each one connecting outbound using ports 40000-60000, opening 100,000 port connections.

Also, it might help to do a sample test with a nicely threaded QA app such as OpenSTA in order to get an idea of how much each server can handle.

Also, try looking into just using simple Perl with the LWP::ConnCache class. You’ll probably get more performance (more connections) that way.

Answered By: djangofan

A solution:

from twisted.internet import reactor, threads
from urlparse import urlparse
import httplib
import itertools

concurrent = 200

def getStatus(ourl):
    url = urlparse(ourl)
    conn = httplib.HTTPConnection(url.netloc)   
    conn.request("HEAD", url.path)
    res = conn.getresponse()
    return res.status

def processResponse(response,url):
    print response, url

def processError(error,url):
    print "error", url#, error

def processedOne():
    if finished.next()==added:

def addTask(url):
    req = threads.deferToThread(getStatus, url)
    req.addCallback(processResponse, url)
    req.addErrback(processError, url)   

for url in open('urllist.txt'):

except KeyboardInterrupt:


[[email protected]:~] wc -l urllist.txt
10000 urllist.txt
[[email protected]:~] time python f.py > /dev/null 

real    1m10.682s
user    0m16.020s
sys 0m10.330s
[[email protected]:~] head -n 6 urllist.txt
[[email protected]:~] python f.py | head -n 6
200 http://www.bix.hu
200 http://www.bix.hu
200 http://www.bix.hu
200 http://www.bix.hu
200 http://www.bix.hu
200 http://www.bix.hu


bix.hu is ~10 ms away from me
godaddy.com: ~170 ms
google.com: ~30 ms
Answered By: Tarnay Kálmán

Twistedless solution:

from urlparse import urlparse
from threading import Thread
import httplib, sys
from Queue import Queue

concurrent = 200

def doWork():
    while True:
        url = q.get()
        status, url = getStatus(url)
        doSomethingWithResult(status, url)

def getStatus(ourl):
        url = urlparse(ourl)
        conn = httplib.HTTPConnection(url.netloc)   
        conn.request("HEAD", url.path)
        res = conn.getresponse()
        return res.status, ourl
        return "error", ourl

def doSomethingWithResult(status, url):
    print status, url

q = Queue(concurrent * 2)
for i in range(concurrent):
    t = Thread(target=doWork)
    t.daemon = True
    for url in open('urllist.txt'):
except KeyboardInterrupt:

This one is slighty faster than the twisted solution and uses less CPU.

Answered By: Tarnay Kálmán

Use grequests , it’s a combination of requests + Gevent module .

GRequests allows you to use Requests with Gevent to make asyncronous HTTP Requests easily.

Usage is simple:

import grequests

urls = [

Create a set of unsent Requests:

>>> rs = (grequests.get(u) for u in urls)

Send them all at the same time:

>>> grequests.map(rs)
[<Response [200]>, <Response [200]>, <Response [200]>, <Response [200]>, <Response [200]>]
Answered By: Akshay Pratap Singh

This twisted async web client goes pretty fast.


from twisted.internet import reactor
from twisted.internet.defer import Deferred, DeferredList, DeferredLock
from twisted.internet.defer import inlineCallbacks
from twisted.web.client import Agent, HTTPConnectionPool
from twisted.web.http_headers import Headers
from pprint import pprint
from collections import defaultdict
from urlparse import urlparse
from random import randrange
import fileinput

pool = HTTPConnectionPool(reactor)
pool.maxPersistentPerHost = 16
agent = Agent(reactor, pool)
locks = defaultdict(DeferredLock)
codes = {}

def getLock(url, simultaneous = 1):
    return locks[urlparse(url).netloc, randrange(simultaneous)]

def getMapping(url):
    # Limit ourselves to 4 simultaneous connections per host
    # Tweak this number, but it should be no larger than pool.maxPersistentPerHost 
    lock = getLock(url,4)
    yield lock.acquire()
        resp = yield agent.request('HEAD', url)
        codes[url] = resp.code
    except Exception as e:
        codes[url] = str(e)

dl = DeferredList(getMapping(url.strip()) for url in fileinput.input())
dl.addCallback(lambda _: reactor.stop())

Answered By: Robᵩ

A solution using tornado asynchronous networking library

from tornado import ioloop, httpclient

i = 0

def handle_request(response):
    global i
    i -= 1
    if i == 0:

http_client = httpclient.AsyncHTTPClient()
for url in open('urls.txt'):
    i += 1
    http_client.fetch(url.strip(), handle_request, method='HEAD')

This code is using non-blocking network I/O and doesn’t have any restriction. It can scale to tens of thousands of open connections. It will run in a single thread but will be a way faster then any threading solution. Checkout non-blocking I/O

Answered By: mher

Things have changed quite a bit since 2010 when this was posted and I haven’t tried all the other answers but I have tried a few, and I found this to work the best for me using python3.6.

I was able to fetch about ~150 unique domains per second running on AWS.

import concurrent.futures
import requests
import time

out = []

tlds = open('../data/sample_1k.txt').read().splitlines()
urls = ['http://{}'.format(x) for x in tlds[1:]]

def load_url(url, timeout):
    ans = requests.head(url, timeout=timeout)
    return ans.status_code

with concurrent.futures.ThreadPoolExecutor(max_workers=CONNECTIONS) as executor:
    future_to_url = (executor.submit(load_url, url, TIMEOUT) for url in urls)
    time1 = time.time()
    for future in concurrent.futures.as_completed(future_to_url):
            data = future.result()
        except Exception as exc:
            data = str(type(exc))


    time2 = time.time()

print(f'Took {time2-time1:.2f} s')
Answered By: Glen Thompson

Create epoll object,
open many client TCP sockets,
adjust their send buffers to be a bit more than request header,
send a request header — it should be immediate, just placing into a buffer,
register socket in epoll object,
do .poll on epoll obect,
read first 3 bytes from each socket from .poll,
write them to sys.stdout followed by n (don’t flush),
close the client socket.

Limit number of sockets opened simultaneously — handle errors when sockets are created. Create a new socket only if another is closed.
Adjust OS limits.
Try forking into a few (not many) processes: this may help to use CPU a bit more effectively.

Answered By: George Sovetov

I know this is an old question, but in Python 3.7 you can do this using asyncio and aiohttp.

import asyncio
import aiohttp
from aiohttp import ClientSession, ClientConnectorError

async def fetch_html(url: str, session: ClientSession, **kwargs) -> tuple:
        resp = await session.request(method="GET", url=url, **kwargs)
    except ClientConnectorError:
        return (url, 404)
    return (url, resp.status)

async def make_requests(urls: set, **kwargs) -> None:
    async with ClientSession() as session:
        tasks = []
        for url in urls:
                fetch_html(url=url, session=session, **kwargs)
        results = await asyncio.gather(*tasks)

    for result in results:
        print(f'{result[1]} - {str(result[0])}')

if __name__ == "__main__":
    import pathlib
    import sys

    assert sys.version_info >= (3, 7), "Script requires Python 3.7+."
    here = pathlib.Path(__file__).parent

    with open(here.joinpath("urls.txt")) as infile:
        urls = set(map(str.strip, infile))


You can read more about it and see an example here.

Answered By: Marius Stănescu

I found that using the tornado package to be the fastest and simplest way to achieve this:

from tornado import ioloop, httpclient, gen

def main(urls):
    Asynchronously download the HTML contents of a list of URLs.
    :param urls: A list of URLs to download.
    :return: List of response objects, one for each URL.

    def fetch_and_handle():
        httpclient.AsyncHTTPClient.configure(None, defaults=dict(user_agent='MyUserAgent'))
        http_client = httpclient.AsyncHTTPClient()
        waiter = gen.WaitIterator(*[http_client.fetch(url, raise_error=False, method='HEAD')
                                    for url in urls])
        results = []
        # Wait for the jobs to complete
        while not waiter.done():
                response = yield waiter.next()
            except httpclient.HTTPError as e:
                print(f'Non-200 HTTP response returned: {e}')
            except Exception as e:
                print(f'An unexpected error occurred querying: {e}')
                print(f'URL '{response.request.url}' has status code <{response.code}>')
        return results

    loop = ioloop.IOLoop.current()
    web_pages = loop.run_sync(fetch_and_handle)

    return web_pages

my_urls = ['url1.com', 'url2.com', 'url100000.com']
responses = main(my_urls)
Answered By: RDRR


Apache Bench is all you need. – A command line computer program (CLI) for measuring the performance of HTTP web servers

A nice blog post for you: https://www.petefreitag.com/item/689.cfm (from Pete Freitag)

Answered By: gia huy

(Note to self for next project)

Python 3 solution using only requests. It’s the simplest and it’s fast, no need for multiprocessing or complicated asynchronous libraries.

The most important aspect is to reuse connections, especially for HTTPS (TLS requires an extra round trip to open). Note that a connection is specific to a subdomain. If you scrape many pages on many domains, you can sort the list of URLs to maximize connection reuse (it effectively sorts by domain).

It will be as fast as any asynchronous code, when given enough threads. (requests releases the python GIL when waiting for the response).

[Production grade code with some logging and error handling]

import logging
import requests
import time
from concurrent.futures import ThreadPoolExecutor, as_completed

# source: https://stackoverflow.com/a/68583332/5994461


# This is how to create a reusable connection pool with python requests.
session = requests.Session()

def get(url):
    response = session.get(url)
    logging.info("request was completed in %s seconds [%s]", response.elapsed.total_seconds(), response.url)
    if response.status_code != 200:
        logging.error("request failed, error code %s [%s]", response.status_code, response.url)
    if 500 <= response.status_code < 600:
        # server is overloaded? give it a break
    return response

def download(urls):
    with ThreadPoolExecutor(max_workers=THREAD_POOL) as executor:
        # wrap in a list() to wait for all requests to complete
        for response in list(executor.map(get, urls)):
            if response.status_code == 200:

def main():
        format='%(asctime)s.%(msecs)03d %(levelname)-8s %(message)s',
        datefmt='%Y-%m-%d %H:%M:%S'

    urls = [


if __name__ == "__main__":
Answered By: user5994461
pip install requests-threads

Example Usage using async/await — send 100 concurrent requests

from requests_threads import AsyncSession

session = AsyncSession(n=100)

async def _main():
    rs = []
    for _ in range(100):
        rs.append(await session.get('http://httpbin.org/get'))

if __name__ == '__main__':

This example works on Python 3 only. You can also provide your own asyncio event loop!

Example Usage using Twisted

from twisted.internet.defer import inlineCallbacks
from twisted.internet.task import react
from requests_threads import AsyncSession

session = AsyncSession(n=100)

def main(reactor):
    responses = []
    for i in range(100):

    for response in responses:
        r = yield response

if __name__ == '__main__':

This example works on both Python 2 and Python 3.

Maybe it can be helpful my repo, one basic example,

Answered By: Milovan Tomašević

Here’s an "async" solution that doesn’t use asyncio, but the lower-level mechanism asyncio uses (on Linux): select(). (Or maybe asyncio uses poll, or epoll, but it’s a similar principle.)

It’s a slightly modified version of the example from PyCurl.

(For simplicity it requests the same URL multiple times, but you can easily modify it to retrieve a bunch of distinct URLs.)

(Another slight modification can make this retrieve the same URL over and over as an infinite loop. Hint: change while urls and handles to while handles, and change while nprocessed<nurls to while 1.)

import pycurl,io,gzip,signal, time, random
signal.signal(signal.SIGPIPE, signal.SIG_IGN)  # NOTE! We should ignore SIGPIPE when using pycurl.NOSIGNAL - see the libcurl tutorial for more info

NCONNS = 2  # Number of concurrent GET requests
url    = 'example.com'
urls   = [url for i in range(0x7*NCONNS)]  # Copy the same URL over and over

# Check args
nurls  = len(urls)
NCONNS = min(NCONNS, nurls)
print("x1b[32m%s x1b[0m(compiled against 0x%x)" % (pycurl.version, pycurl.COMPILE_LIBCURL_VERSION_NUM))
print(f'x1b[37m{nurls} x1b[[email protected] x1b[92m{NCONNS}x1b[0m')

# Pre-allocate a list of curl objects
m         = pycurl.CurlMulti()
m.handles = []
for i in range(NCONNS):
  c = pycurl.Curl()
  c.setopt(pycurl.FOLLOWLOCATION,  1)
  c.setopt(pycurl.MAXREDIRS,       5)
  c.setopt(pycurl.CONNECTTIMEOUT,  30)
  c.setopt(pycurl.TIMEOUT,         300)
  c.setopt(pycurl.NOSIGNAL,        1)

handles    = m.handles  # MUST make a copy?!
nprocessed = 0
while nprocessed<nurls:

  while urls and handles:  # If there is an url to process and a free curl object, add to multi stack
    url   = urls.pop(0)
    c     = handles.pop()
    c.buf = io.BytesIO()
    c.url = url  # store some info
    c.t0  = time.perf_counter()
    c.setopt(pycurl.URL,        c.url)
    c.setopt(pycurl.WRITEDATA,  c.buf)
    c.setopt(pycurl.HTTPHEADER, [f'user-agent: {random.randint(0,(1<<256)-1):x}', 'accept-encoding: gzip, deflate', 'connection: keep-alive', 'keep-alive: timeout=10, max=1000'])

  while 1:  # Run the internal curl state machine for the multi stack
    ret, num_handles = m.perform()
    if ret!=pycurl.E_CALL_MULTI_PERFORM:  break

  while 1:  # Check for curl objects which have terminated, and add them to the handles
    nq, ok_list, ko_list = m.info_read()
    for c in ok_list:
      t1 = time.perf_counter()
      reply = gzip.decompress(c.buf.getvalue())
      print(f'x1b[33mGET  x1b[32m{t1-c.t0:.3f}  x1b[37m{len(reply):9,}  x1b[0m{reply[:32]}...')  # x1b[35m{psutil.Process(os.getpid()).memory_info().rss:,} x1b[0mbytes')
    for c, errno, errmsg in ko_list:
      print('x1b[31mFAIL {c.url} {errno} {errmsg}')
    nprocessed = nprocessed + len(ok_list) + len(ko_list)
    if nq==0: break

  m.select(1.0)  # Currently no more I/O is pending, could do something in the meantime (display a progress bar, etc.). We just call select() to sleep until some more data is available.

for c in m.handles:
Answered By: étale-cohomology

Scrapy framework will solve your problem fast and professionally. It will also cache all the requests, so that you can rerun the failed ones only later on.

Save this script as quotes_spider.py.

# quote_spiders.py
import json
import string
import scrapy
from scrapy.crawler import CrawlerProcess
from scrapy.item import Item, Field

class TextCleaningPipeline(object):
    def _clean_text(self, text):
        text = text.replace('“', '').replace('”', '')
        table = str.maketrans({key: None for key in string.punctuation})
        clean_text = text.translate(table)
        return clean_text.lower()

    def process_item(self, item, spider):
        item['text'] = self._clean_text(item['text'])
        return item

class JsonWriterPipeline(object):
    def open_spider(self, spider):
        self.file = open(spider.settings['JSON_FILE'], 'a')

    def close_spider(self, spider):

    def process_item(self, item, spider):
        line = json.dumps(dict(item)) + "n"
        return item

class QuoteItem(Item):
    text = Field()
    author = Field()
    tags = Field()
    spider = Field()

class QuoteSpider(scrapy.Spider):
    name = "quotes"

    def start_requests(self):
        urls = [
            # ...
        for url in urls:
            yield scrapy.Request(url=url, callback=self.parse)

    def parse(self, response):
        for quote in response.css('div.quote'):
            item = QuoteItem()
            item['text'] = quote.css('span.text::text').get()
            item['author'] = quote.css('small.author::text').get()
            item['tags'] = quote.css('div.tags a.tag::text').getall()
            item['spider'] = self.name
            yield item

if __name__ == '__main__':
    settings = dict()
    settings['USER_AGENT'] = 'Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1)'
    settings['HTTPCACHE_ENABLED'] = True
    settings['CONCURRENT_REQUESTS'] = 20
    settings['JSON_FILE'] = 'items.jl'
    settings['ITEM_PIPELINES'] = dict()
    settings['ITEM_PIPELINES']['__main__.TextCleaningPipeline'] = 800
    settings['ITEM_PIPELINES']['__main__.JsonWriterPipeline'] = 801

    process = CrawlerProcess(settings=settings)

followed by

$ pip install Scrapy
$ python quote_spiders.py 

To fine tune the scraper adjust the CONCURRENT_REQUESTS and CONCURRENT_REQUESTS_PER_DOMAIN settings accordingly.

Answered By: Levon
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