Re: Comments on the fastestmirror plugin

On Fri, 2010-03-12 at 14:21 +0000, Fred Williams wrote:
On 12 March 2010 14:08, Patrick O'Callaghan <pocallaghan@xxxxxxxxx>
wrote:
The yum fastestmirror plugin (yum-plugin-fastestmirror) claims
to
evaluate the speed of a bunch of repo mirrors and use the
fastest one
relative to the user's location.

However AFAIK what it *actually* does is make a test
connection to the
to the candidate mirrors and order them according to response
time,
which in many cases is dominated by network latency, which can
distort
the results. For well-connected user machines in first-world
countries
it probably doesn't matter much, and may have the beneficial
effect of
spreading the load over a wider range of mirrors, but for
those of us in
a less privileged position it can matter a lot. Ironically,
these are
the cases where such an optimization could do the most good.

A case in point: I live in Venezuela and on several recent
occasions yum
decided that my closest repo was in Puerto Rico, which as the
packet
flies is probably true. However the b/w I got as a result was
around 2
or 3kbps.

I tried renewing the mirror cache. No difference (ping times
tend not to
vary much).

I then manually edited the /var/cache/yum/timedhosts.txt file
to bias
the results against the mirror yum was choosing (I made it
worst rather
than best). Oddly, it again made no difference! It seems
there's a
cunning hidden cache of these results that I don't know about.
Finally I
disabled the plugin completely and got decent b/w without it.

Perhaps we should be considering some kind of BitTorrent
version of the
repos in which the mirrors are seeds and the users are
leeches, though I
realize that this is harder than it looks, particularly when
taking into
account the synching of the mirrors themselves.

poc

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Perhaps not so difficult - though I've never used them myself, I
recall that in the Debian, if not Ubuntu (Sometimes hard to tell)
repositories are some packages that allow for bittorrent fetching of
deb packages - perhaps if they're still relevent and working, they
could be used as a base to create a means of implementing the same,
maybe as a plugin for Yum or similar.
Theoretically, I think the only main differences are the download
protocol. HTTP/FTP or BitTorrent. Once downloaded the package can
still be used in the same way, there's no difference there.
The main downside I see to it is that those users on an ISP which
throttles BitTorrent will suffer, and have to go back to standard
downloads, but if both are provided, then no issue. Or at least very
little.
Just my 2p. Or 2c, depending on your currency.

Interesting. I'll see what I can can find on BT use in the Debian/Ubuntu
world.

poc

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