[Pdns-dev] What will pdns do when a fast dns server become slow and become fast again?

jacky jacky.wucheng at gmail.com
Fri Dec 27 08:29:27 CET 2013


hi, Aki tnuomi,  
Thank you for  suggestion. I found pdns always get the fastest one from the front of result returned by function "SyncRes::shuffleInSpeedOrder”. If a slow one at the back has no opportunity to be choosed, how pdns know it become fast. I can not find the source code make pdns query the slow one.  

on the other hand, I found there is a houseKeeping thread which will erase the stale speed value of a dns server . If a slow dns at the back of t_sstorage->nsSpeeds map, it will be erased because of rarely to be queried, and only fast dns server will have its speed updated by this code "  t_sstorage->nsSpeeds[*tns].submit(*remoteIP, lwr.d_usec, &d_now);” at syncres.cc:1003.
. And then, only dns servers which are mostly queried will stay in t_sstorage->nsSpeeds map. It make me puzzled.

--  
jacky


On Friday, December 27, 2013 at 3:08 PM, Aki Tuomi wrote:

> On Thu, Dec 26, 2013 at 10:34:23PM +0800, jacky wrote:
> > hi, all,  
> > I think may be it is a question more suitable to dev maillist, so I submit it here. If I made a mistake , please let me know. Thanks.
> >  
> > I'am reading the source code of pdns-recursor-3.5.3. There is question I can not understand.
> > When a authoritative dns server become slow because of overload, pdns-recursor will move it backwards in the  
> > t_sstorage->nsSpeeds map, and then a faster dns server will be used preferred. But when the dns server recoverd  
> > from overload and become fast again, what will pdns-recursor do about it ? Will pdns-recursor move it forward  
> > in speed map? I can't find relevant source code. Any suggestion?
> >  
> > --  
> > jacky
> >  
>  
>  
> Hi!
>  
> It works by moving the fastest one on top.  
>  
> > _______________________________________________
> > Pdns-dev mailing list
> > Pdns-dev at mailman.powerdns.com (mailto:Pdns-dev at mailman.powerdns.com)
> > http://mailman.powerdns.com/mailman/listinfo/pdns-dev
> >  
>  
>  
>  


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