[Django]-Python Asynchronous Reverse DNS Lookups

I discovered my main issue was IPs failing to resolve and thus sockets not obeying their set timeouts and failing after 30 seconds. See Python 2.6 urlib2 timeout issue.

adns-python was a no-go because of its lack of support for IPv6 (without patches).

After searching around I found this: Reverse DNS Lookups with dnspython and implemented a similar version in my code (his code also uses an optional thread pool and implements a timeout).

In the end I used dnspython with a concurrent.futures thread pool for asynchronous reverse DNS lookups (see Python: Reverse DNS Lookup in a shared hosting and Dnspython: Setting query timeout/lifetime). With a timeout of 1 second this cut runtime from about 22 minutes to about 16 seconds on 2500 IP addresses. The large difference can probably be attributed to the Global Interpreter Lock on sockets and the 30 second timeouts.

Code Snippet:

import concurrent.futures
from dns import resolver, reversename
dns_resolver = resolver.Resolver()
dns_resolver.timeout = 1
dns_resolver.lifetime = 1
ips = [...]
results = []

with concurrent.futures.ThreadPoolExecutor(max_workers = 16) as pool:
    results = list(pool.map(get_hostname_from_ip, ips))

def get_hostname_from_ip(ip):
    try:
        reverse_name = reversename.from_address(ip)
        return dns_resolver.query(reverse_name, "PTR")[0].to_text()[:-1]
    except:
        return ""