[dns-operations] good async DNS library

[pengyonghua at virgilio.it]

or try this one:
https://metacpan.org/pod/AnyEvent::DNS


> On April 26, 2019 at 11:43 AM Klaus Darilion <klaus.mailinglists at pernau.at> wrote:
> 
> 
> 
> 
> Am 26.04.2019 um 05:04 schrieb Doug Barton:
> > On 4/25/19 2:08 PM, Klaus Darilion wrote:
> >> Hi all!
> >>
> >> For various monitoring scripts we use Perl's NET::DNS and
> >> Net::DNS::Async. Unfortunately they have various problems, ie
> >> Net::DNS::Async does not support DNSSEC and sending to other ports
> >> than 54, with Net::DNS's timeout/retries settings I never get the
> >> expected results ....
> >>
> >> Can someon recommend a DNS library (Perl, Python or PHP preferred)
> >> that supports:
> >> - async resolving
> >> - setting DO bit
> >> - EDNS0 options
> >> - proper timeout handling
> >> - sending queries to non-standard ports
> >> - (optional: TCP fallback)
> > 
> > Maybe if you sent your queries to port 53 you'd have better results?  ;)
> > 
> > Seriously though, it would be easier to help if you talked about what
> > you're trying to accomplish, rather than starting out with a proposed
> > solution. Also, please define what you mean by async, and why you think
> > you need it. (I know those may sounds like dumb questions, but it will
> > be easier to help you if you answer them.)
> 
> My current task is to monitor zone freshness on our Anycast cloud. So,
> every second, I send SOA requests to every of our 30 global nodes and
> check the received serial.
> 
> I currently use Net::DNS::Async as sequential scanning takes to long -
> hence with async. I patched Async to allow sending also to non-standard
> ports (with only 1 unicast IP, but multiple name server processes, I
> have to use different ports). But there is still the problem that
> Timeouts are only with 1 second granularity, but I need timeouts < 1s.
> 
> That's why I look for a good replacement of Net::DNS::Async.
> 
> 
> > I have done a fair bit with both Perl and Net::DNS(::SEC), and while it
> > has a lot of warts, they are improving with the recent few years of
> > active maintenance. The timeout/retry code tends to do what it should
> > do, whether that's what you intended or not.
> 
> Last time I checked it was also not possible to use timeouts < 1 second
> and no retries. But his may have changed meanwhile.
> 
> > If you have a requirement
> > for stricter timeouts and/or predictable retries you'd be better off
> > using Net::DNS::Packet, and use Perl's IO::Socket module to send; rather
> > than using any of the pre-baked methods for queries in Net::DNS. I
> > combine that with alarms in situations where I need stricter timeouts,
> > retries with progressive backoff, etc. That said, do enough of that work
> > yourself and it will make you more appreciative of some of the oddities
> > of what Net::DNS is doing.
> 
> Sounds reasonable, If I would only have more time to implement it myself ;-)
> 
> Thanks
> Klaus
> 
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