clients-per-query message is harmful or not?

Mark Andrews marka at isc.org
Wed Dec 23 03:38:18 UTC 2009


In message <BLU149-W57A261F59F90728F956CEA85800 at phx.gbl>, MontyRee writes:
> 
> Hello, all.
>  
> my system is centos 4.x, bind 9.5.1-P3 and only recursion is allowed from some ranges.
> 
> I can see lots of messages like below.
> so if I didn't set any clients-per-query value,some clients' queries may be droppped or not? 

clients-per-query is designed to prevent the nameserver being
overwhelmed by a given query that doesn't resolve.  It sets the
number of simultanious clients that are acutally recursing on a
given name.  It value is increased if there is a successful resolution
of that query after dropping some clients then slowly decays over time.
Note UDP clients are expected to retry.

clients-per-query reflects how many clients ask for a busy name/type in
the time it takes to resolve that name/type.  If it takes 200 ms resolve
the query and you need 20 clients-per-query then the name/type is being
asked for around 100 times a second.

> If some queries can be dropped,I want to set like "clients-per-query 0".   

You actually want to set clients-per-query to around 20 based on
these logs, the default is 10.
 
> 05-Oct-2009 16:04:46.228 resolver: notice: clients-per-query decreased to 14
> 05-Oct-2009 16:14:47.337 resolver: notice: clients-per-query increased to 19
> 05-Oct-2009 16:34:47.338 resolver: notice: clients-per-query decreased to 18
> 05-Oct-2009 16:54:47.339 resolver: notice: clients-per-query decreased to 17
> 05-Oct-2009 17:01:55.424 resolver: notice: clients-per-query increased to 22
> 05-Oct-2009 20:20:26.252 resolver: notice: clients-per-query increased to 15
> 05-Oct-2009 20:40:26.253 resolver: notice: clients-per-query decreased to 14
> 05-Oct-2009 21:00:26.253 resolver: notice: clients-per-query decreased to 13
> 05-Oct-2009 21:11:26.298 resolver: notice: clients-per-query increased to 15
> 
>  
>  
> Thanks in advance.
-- 
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: marka at isc.org



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