note that the timeout
that gets passed around by urllib
applies to the "wrong thing". that is each individual network operation (e.g. hostname resolution, socket connection, sending headers, reading a few bytes of the headers, reading a few more bytes of the response) each get this same timeout applied. hence passing a "timeout" of 10 seconds could allow a large response to continue for hours
if you want to stick to built in Python code then it would be nice to use a thread to do this, but it doesn't seem to be possible to cancel running threads nicely. an async library like trio
would allow better timeout and cancellation handling, but we can make do by using the multiprocessing
module instead:
from urllib.request import Request, urlopen
from multiprocessing import Process
from time import perf_counter
def _http_ping(url):
req = Request(url, method='HEAD')
print(f'trying {url!r}')
start = perf_counter()
res = urlopen(req)
secs = perf_counter() - start
print(f'response {url!r} of {res.status} after {secs*1000:.2f}ms')
res.close()
def http_ping(url, timeout):
proc = Process(target=_http_ping, args=(url,))
try:
proc.start()
proc.join(timeout)
success = not proc.is_alive()
finally:
proc.terminate()
proc.join()
proc.close()
return success
you can use https://httpbin.org/ to test this, e.g:
http_ping('https://httpbin.org/delay/2', 1)
should print out a "trying" message, but not a "response" message. you can adjust the delay time and timeout to explore how this behaves...
note that this spins up a new process for each request, but as long as you're doing this less than a thousand pings a second it should be OK