Re: Working with a local DNS cache

[Adam Langley <agl imperialviolet org>]

On Tue, Sep 22, 2009 at 11:11 PM, Dan Williams <dcbw redhat com> wrote:
> Colin and I discussed this last week too; is the Chromium cache a
> machine-global cache (ie, running other programs would also route
> requests through the cache), or does Chromium want the DNS data in
> parallel with the normal glibc resolver?  Seems like it is a global
> cache, right?

Sorry, I think the word 'Chromium' is confusing here (which is
probably my fault since I introduced it). Chromium is just another
process which uses DNS (although it's a pretty heavy user due to
prefetching[1]). There's a DNS cache inside of Chromium itself, but
it's very short lived (on the order of a few seconds) and exists only
to merge DNS lookups when we simultaneously open multiple connections
to the same host. This cache is per browser process.

The DNS cache which implements the DBus interface[2] is a real DNS
cache and is designed to be machine global. (It's a hacked up version
of djbdns[3]). It exists only because I'm sure that some distros would
balk at including BIND by default and I wanted another answer if/when
I try to get them to enable local DNS caching by default. The DBus
interface name includes 'chromium' only because I didn't have a better
name at the time. It's nothing to do with the Chromium codebase.

I hope that clears things up.


Cheers

AGL

[1] http://blog.chromium.org/2008/09/dns-prefetching-or-pre-resolving.html
[2] http://github.com/agl/local-dns-cache
[3] http://cr.yp.to/djbdns.html

-- 
Adam Langley agl imperialviolet org http://www.imperialviolet.org