I am trying to use urllib3 in simple thread to fetch several wiki pages.
The script will
Create 1 connection for every thread (I don't understand why) and Hang forever.
Any tip, advice or simple example of urllib3 and threading
import threadpool
from urllib3 import connection_from_url
HTTP_POOL = connection_from_url(url, timeout=10.0, maxsize=10, block=True)
def fetch(url, fiedls):
kwargs={'retries':6}
return HTTP_POOL.get_url(url, fields, **kwargs)
pool = threadpool.ThreadPool(5)
requests = threadpool.makeRequests(fetch, iterable)
[pool.putRequest(req) for req in requests]
@Lennart's script got this error:
http://en.wikipedia.org/wiki/2010-11_Premier_LeagueTraceback (most recent call last):
File "/usr/local/lib/python2.7/dist-packages/threadpool.py", line 156, in run
http://en.wikipedia.org/wiki/List_of_MythBusters_episodeshttp://en.wikipedia.org/wiki/List_of_Top_Gear_episodes http://en.wikipedia.org/wiki/List_of_Unicode_characters result = request.callable(*request.args, **request.kwds)
File "crawler.py", line 9, in fetch
print url, conn.get_url(url)
AttributeError: 'HTTPConnectionPool' object has no attribute 'get_url'
Traceback (most recent call last):
File "/usr/local/lib/python2.7/dist-packages/threadpool.py", line 156, in run
result = request.callable(*request.args, **request.kwds)
File "crawler.py", line 9, in fetch
print url, conn.get_url(url)
AttributeError: 'HTTPConnectionPool' object has no attribute 'get_url'
Traceback (most recent call last):
File "/usr/local/lib/python2.7/dist-packages/threadpool.py", line 156, in run
result = request.callable(*request.args, **request.kwds)
File "crawler.py", line 9, in fetch
print url, conn.get_url(url)
AttributeError: 'HTTPConnectionPool' object has no attribute 'get_url'
Traceback (most recent call last):
File "/usr/local/lib/python2.7/dist-packages/threadpool.py", line 156, in run
result = request.callable(*request.args, **request.kwds)
File "crawler.py", line 9, in fetch
print url, conn.get_url(url)
AttributeError: 'HTTPConnectionPool' object has no attribute 'get_url'
After adding import threadpool; import urllib3
and tpool = threadpool.ThreadPool(4)
@user318904's code got this error:
Traceback (most recent call last):
File "crawler.py", line 21, in <module>
tpool.map_async(fetch, urls)
AttributeError: ThreadPool instance has no attribute 'map_async'
Obviously it will create one connection per thread, how should else each thread be able to fetch a page? And you try to use the same connection, made from one url, for all urls. That can hardly be what you intended.
This code worked just fine:
import threadpool
from urllib3 import connection_from_url
def fetch(url):
kwargs={'retries':6}
conn = connection_from_url(url, timeout=10.0, maxsize=10, block=True)
print url, conn.get_url(url)
print "Done!"
pool = threadpool.ThreadPool(4)
urls = ['http://en.wikipedia.org/wiki/2010-11_Premier_League',
'http://en.wikipedia.org/wiki/List_of_MythBusters_episodes',
'http://en.wikipedia.org/wiki/List_of_Top_Gear_episodes',
'http://en.wikipedia.org/wiki/List_of_Unicode_characters',
]
requests = threadpool.makeRequests(fetch, urls)
[pool.putRequest(req) for req in requests]
pool.wait()
Thread programming is hard, so I wrote workerpool to make exactly what you're doing easier.
More specifically, see the Mass Downloader example.
To do the same thing with urllib3, it looks something like this:
import urllib3
import workerpool
pool = urllib3.connection_from_url("foo", maxsize=3)
def download(url):
r = pool.get_url(url)
# TODO: Do something with r.data
print "Downloaded %s" % url
# Initialize a pool, 5 threads in this case
pool = workerpool.WorkerPool(size=5)
# The ``download`` method will be called with a line from the second
# parameter for each job.
pool.map(download, open("urls.txt").readlines())
# Send shutdown jobs to all threads, and wait until all the jobs have been completed
pool.shutdown()
pool.wait()
For more sophisticated code, have a look at workerpool.EquippedWorker (and the tests here for example usage). You can make the pool be the toolbox
you pass in.
Here is my take, a more current solution using Python3 and concurrent.futures.ThreadPoolExecutor
.
import urllib3
from concurrent.futures import ThreadPoolExecutor
urls = ['http://en.wikipedia.org/wiki/2010-11_Premier_League',
'http://en.wikipedia.org/wiki/List_of_MythBusters_episodes',
'http://en.wikipedia.org/wiki/List_of_Top_Gear_episodes',
'http://en.wikipedia.org/wiki/List_of_Unicode_characters',
]
def download(url, cmanager):
response = cmanager.request('GET', url)
if response and response.status == 200:
print("+++++++++ url: " + url)
print(response.data[:1024])
connection_mgr = urllib3.PoolManager(maxsize=5)
thread_pool = ThreadPoolExecutor(5)
for url in urls:
thread_pool.submit(download, url, connection_mgr)
Some remarks
- My code is based on a similar example from the
Python Cookbook
by Beazley and Jones.
- I particularly like the fact that you only need a standard module besides
urllib3
.
- The setup is extremely simple, and if you are only going for side-effects in
download
(like printing, saving to a file, etc.), there is no additional effort in joining the threads.
- If you want something different,
ThreadPoolExecutor.submit
actually returns whatever download
would return, wrapped in a Future
.
- I found it helpful to align the number of threads in the thread pool with the number of
HTTPConnection
's in a connection pool (via maxsize
). Otherwise you might encounter (harmless) warnings when all threads try to access the same server (as in the example).
I use something like this:
#excluding setup for threadpool etc
upool = urllib3.HTTPConnectionPool('en.wikipedia.org', block=True)
urls = ['/wiki/2010-11_Premier_League',
'/wiki/List_of_MythBusters_episodes',
'/wiki/List_of_Top_Gear_episodes',
'/wiki/List_of_Unicode_characters',
]
def fetch(path):
# add error checking
return pool.get_url(path).data
tpool = ThreadPool()
tpool.map_async(fetch, urls)
# either wait on the result object or give map_async a callback function for the results