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async_dns.py
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async_dns.py
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#!/usr/bin/python
#
# Peteris Krumins (peter@catonmat.net)
# http://www.catonmat.net -- good coders code, great reuse
#
# Asynchronous DNS Resolution. v1.0.
#
# Read more about this code at:
# http://www.catonmat.net/blog/asynchronous-dns-resolution
#
import adns
from time import time
class AsyncResolver(object):
def __init__(self, hosts, intensity=100):
"""
hosts: a list of hosts to resolve
intensity: how many hosts to resolve at once
"""
self.hosts = hosts
self.intensity = intensity
self.adns = adns.init()
def resolve(self):
""" Resolves hosts and returns a dictionary of { 'host': 'ip' }. """
resolved_hosts = {}
active_queries = {}
host_queue = self.hosts[:]
def collect_results():
for query in self.adns.completed():
answer = query.check()
host = active_queries[query]
del active_queries[query]
if answer[0] == 0:
ip = answer[3][0]
resolved_hosts[host] = ip
elif answer[0] == 101: # CNAME
query = self.adns.submit(answer[1], adns.rr.A)
active_queries[query] = host
else:
resolved_hosts[host] = None
def finished_resolving():
return len(resolved_hosts) == len(self.hosts)
while not finished_resolving():
while host_queue and len(active_queries) < self.intensity:
host = host_queue.pop()
query = self.adns.submit(host, adns.rr.A)
active_queries[query] = host
collect_results()
return resolved_hosts
if __name__ == "__main__":
host_format = "www.host%d.com"
number_of_hosts = 20000
hosts = [host_format % i for i in range(number_of_hosts)]
ar = AsyncResolver(hosts, intensity=500)
start = time()
resolved_hosts = ar.resolve()
end = time()
print "It took %.2f seconds to resolve %d hosts." % (end-start, number_of_hosts)