Query an array of DNS records with dnspython, and proceed to the next element based on a custom timeout

Question

I'm querying a bunch of DNS records with dnspython, it seems to timeout when no reply is received (dns.exception.Timeout: The DNS operation timed out after 30.0006685256958 seconds).

Here's the function:

def dnstest(domain):
    dnsrecords = []
    record_types = ['A', 'AAAA', 'CNAME', 'MX', 'SRV', 'TXT', 'SOA', 'NS']
    dnsResolver = dns.resolver.Resolver()
    for record in record_types:
        dnsAnswer = dnsResolver.query(domain, record)
        for rdata in dnsAnswer:
            dnsrecords.append(rdata)
    return(dnsrecords)

print(dnstest("github.com"))

whereas, if I query the DNS records that exist, an answer is received:
dnsAnswer = dnsResolver.query(domain, 'A')

I'm guessing this is because certain records (such as SRV, AAAA etc.) doesn't exist for github.com. However, they do exist for other domains. Is there a way I can include a timeout (like say, 5 seconds) per query within the for loop?
Something like -
if no response in 5 seconds, move to next element in the array
Or is there a better approach to exclude non-existent records?

score 0 · Answer 1 · answered Aug 22 '17 at 05:24

The following worked for me after some quick googling.

import dns.resolver

def dnstest(domain):
    dnsrecords = []
    record_types = ['A', 'AAAA', 'CNAME', 'MX', 'SRV', 'TXT', 'SOA', 'NS']
    dnsResolver = dns.resolver.Resolver()
    dnsResolver.timeout = 1
    dnsResolver.lifetime = 1
    for record in record_types:
        try:
            dnsAnswer = dnsResolver.query(domain, record)
            for rdata in dnsAnswer:
                dnsrecords.append(rdata)
        except:
            pass

    return(dnsrecords)

Query an array of DNS records with dnspython, and proceed to the next element based on a custom timeout

1 Answers1