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Re: Why does performance crap out when lookupd...

Giuliano,

I'm not sure but I think the DNSAgent is still a work in progress as far as
"emulating" named as a caching-only / single host local server ( which can
help with the performances sendmail et al.)

I think it would be risky, at this point to turn that on. You would have to
install things like root.cache, rev and zone files into netinfo. They don't
exist yet. I think it might actually support inserting them manually if we
had a current list of verified functioning key, value pairs. But...

As of right now, it thinks it is the local named (perhaps why the udp query
followed by the tcp query and the unique (XID) id? ) But, it really can't do
it without the missing pieces.

And I readily admit I am still trying to get a handle on where everything
lives. You may be further ahead of me. It would be nice to have some sort of
design document as a road map. As someone here suggested the most likely way
to get that would be to reverse engineer the thing while making notations.

I am still not convinced that using localized multi-threaded mechanisms with
timers and message ids to implement a very heavy, hierarchical UDP based
distributed protocol in a multi-protocol&purpose daemon is a good approach.
And I suspect the developers are finding that out...

Best approach might be to just hand the whole thing off ala inetd to a local
named or the new lightweight resolver (if it works). Let the app sit on the
response, not the entire operating system.

For desktop appliances the centralized "caching" described will provide
negligible improvement with the potential for many negative side effects.
I believe a number of posts have borne this out. DNS has to adapt to just
about every application domain where Internet access is desirable. Whereas
LDAP, NIS, and the like are specific to the Enterprise.


-- P.

>
> Giuliano Gavazzi <email@hidden>
>
> I have just noticed in man lookupd something that might explain some
> of the problems related to DNS and lookupd:
>
> The cache validation strategy in the NetInfo, NIS, and Flat File agents
> makes validation as fast and inexpensive as possible. At present, there
> is no cache validation for DNS. That means that objects originally ob-
> tained from DNS will only be available from the cache if validation is
> disabled for hosts.
>
> indeed lookupd -statistics shows that the cache agents never replies
> successfully to a host ip_address or host name query.
>
> To enable caching for host lookups one should set ValidateCache to NO
> for host category of the CacheAgent. This seems not to work, perhaps
> the manual page is not correct or I have set this improperly.
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