[Yum-devel] [PATCH] fastestmirror: Do not include DNS lookup in host timing.

Tuomo Soini tis at foobar.fi
Thu Feb 9 09:57:41 UTC 2012


On Mon, 19 Dec 2011 10:27:03 -0500
seth vidal <skvidal at fedoraproject.org> wrote:

> On Mon, 19 Dec 2011 13:51:02 +0100
> Zdeněk Pavlas <zpavlas at redhat.com> wrote:
> 
> > The fastestmirror plugin tries to find the fastest mirror
> > by timing a null TCP connect(), so usually 2x RTT.
> > 
> > However, the value measured includes host DNS lookup overhead,
> > which is completely unrelated.  So, perform it outside
> > the connect() statement.
> 
> 
> 
> Applying minor patches to fastestmirror doesn't fix the underlying
> problem that fastestmirror doesn't measure what you actually care
> about
> - transfer of files - not connect() time.

I must disagree. This patch fixes fastestmirror so it actually uses
mirror server with lowest latency - this fixes issues where random
server from same domain (same dns latency) is selected. So with this
patch fastestmirror selects always the server I have behind gigabit
ethernet and not the other server which is behind dsl link.

This is even more obvious because there is very little difference
between latencies of those two sites, dns latency is much longer than
slower network path latency...

I'd ACK this patch until there is better implementation - this is
really worth fixing.

-- 
Tuomo Soini <tis at foobar.fi>
Foobar Linux services
+358 40 5240030
Foobar Oy <http://foobar.fi/>


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