DNS::hostByAddress can be slow about poco HOT 5 CLOSED

Interesting observation. I remember that I've put in AI_ADDRCONFIG for some specific reason, but I cannot remember what it was.
Will have to dig it out.

Günter

Günter Obiltschnig
Applied Informatics Software Engineering GmbH
A-9182 Maria Elend | Maria Elend 96/4 | www.appinf.com
P: +43 4253 32596 M: +43 676 5166737 F: +43 4253 32096

Company Registration: FN 276491 f | Landesgericht Klagenfurt
Managing Director: DI Günter Obiltschnig

On 18.01.2013, at 19:48, karlr42 wrote:

I've found that for some domains, resolving takes on the order of 5 seconds in my environment. This is evident using HTTPSClientSession and I've put together a minimal test case here:

https://gist.github.com/4566844

From my testing it looks like the issue is IPv6 related and is down to the AI_ADDRCONFIG flag passed to the getaddrinfo system call by DNS::hostByAddress. If I remove that flag and recompile the library(I'm using 1.4.6 downloaded from the main site) and then try my test case, resolution takes the normal(<1 sec) amount of time. I have also replicated the problem and made a small test case using just C and directly calling getaddrinfo. : https://gist.github.com/4566462

My setup is:
Ubuntu 12.10 64-bit
Configured Poco(1.4.6) with --no-tests --no-samples --omit=Data/OBDC,Data/MySQL
My ifconfig is : https://gist.github.com/4566285 and the interface connected to the outside world is eth1.

I think the issue is down to the fact the domain in question has no AAAA records but my local machine has an assigned IPv6 address. So getaddrinfo, following the AI_ADDRCONFIG flag, makes a request an AAAA record, which timesout, and then makes a request for an A record, thus causing the delay. Or there is some other peculiarity with the DNS records for this site and others I've tried(myjoyonline.com, for example), I'm not sure.

So maybe this isn't necessarily a bug on your side, but I thought I would bring it to your attention anyway- this issue doesn't seem to affect any other application I use in this environment. I have patched Net::DNS::hostByAddress locally for now to remove the AI_ADDRCONFIG flag and my application(a proxy server making lots of DNS requests) is a lot faster now.

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Maybe expose it in hostByName() and hostByAddress(), with default AI_CANONNAME | AI_ADDRCONFIG ?

On another note, FYI apparently something has changed in appinf DNS and test fails now. Not a big deal, just little bit annoying.

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apparently something has changed in appinf DNS and test fails now

There was 1 failure: 
 1: N7CppUnit10TestCallerI7DNSTestEE.testHostByName
    "he1.name() == "dnstest.appinf.com" || he1.name() == "aliastest.appinf.com""
    in "src/DNSTest.cpp", line 64

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I fixed the DNS records for dnstest and aliastest and the test should work again soon (after the change propagates through).

Günter

Günter Obiltschnig
Applied Informatics Software Engineering GmbH
A-9182 Maria Elend | Maria Elend 96/4 | www.appinf.com
P: +43 4253 32596 M: +43 676 5166737 F: +43 4253 32096

Company Registration: FN 276491 f | Landesgericht Klagenfurt
Managing Director: DI Günter Obiltschnig

On 25.01.2013, at 06:43, Aleksandar Fabijanic wrote:

apparently something has changed in appinf DNS and test fails now

There was 1 failure:
1: N7CppUnit10TestCallerI7DNSTestEE.testHostByName
"he1.name() == "dnstest.appinf.com" || he1.name() == "aliastest.appinf.com""
in "src/DNSTest.cpp", line 64

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I could not reproduce this problem with my DNS, Windows 8, VS 2012. Flags can now be passed by user, if not explicitly passed, defaulting to AI_CANONNAME | AI_ADDRCONFIG. Will be in 1.5.2

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