如何使用Python同时发送10,000个HTTP请求

Question

I need to get HTTP GET response from the top 1-million domains, and I want to open as much concurrent thread as possible so I can finish it faster. The only relevant post that I found is What is the fastest way to send 100,000 HTTP requests in Python? and the solution uses concurrent.futures works as expected.

However, the problem is as I am setting the number of workers higher, the performance gain seems to stagnant, ie, I do not sense any difference if I set number of workers to 1000 or 10,000. I run it on paid EC2 instance and I can see I am only using a fraction of the available CPU and memory. Not sure what happened, is there a limit that how many concurrent thread that I can create? Can I override the limit?

Answer 1

I find there isn't much difference between urllib3 and requests (requests might be a shade faster). I would use an async library since this is a prime use case.

from gevent import monkey, spawn, joinall
monkey.patch_all()
import urllib3, certifi
from time import time

threads = []
url = 'https://www.google.com'
upool = urllib3.PoolManager(cert_reqs='CERT_REQUIRED', ca_certs=certifi.where(), num_pools=20,  block=False)

t0 = time()
for i in xrange(10000):
    threads.append(spawn(upool.request,'GET',url))

x = joinall(threads)

print len(x)
print time() - t0

Notice you can cap the number of connections used at once by adding true to block .

* UPDATE FOR MULTIPROCESSING *

from gevent import monkey, spawn, joinall
monkey.patch_all()
import urllib3, certifi
from time import time
import gipc

worker = {}
num_threads = 1000

def fetch(num_threads, url, cpu):
    print('starting {}'.format(cpu))
    threads = []
    upool = urllib3.PoolManager(cert_reqs='CERT_REQUIRED', ca_certs=certifi.where(), num_pools=20, block=False)
    t0 = time()
    for i in xrange(num_threads):
        threads.append(spawn(upool.request, 'GET', url))
    x = joinall(threads)
    return x, time() - t0

def count_cpus():
    import multiprocessing
    cpus = multiprocessing.cpu_count()
    print(cpus)
    return cpus

def multicore(url):
    global worker
    with gipc.pipe() as (r,w):
        for cpu in range(count_cpus()):
            worker[str(cpu)] = gipc.start_process(target=fetch, args=(num_threads, url, cpu))
    for work in worker:
        worker[work].join()
    return worker

if __name__ == '__main__':
    multicore('https://www.google.com')

    for work in worker:
        print worker[work]