[mirror-admin] Your bandwidth # in Fedora MirrorManager is meaningful now

[Matt Domsch]

Action needed from each mirror admin: go into
https://admin.fedoraproject.org/mirrormanager and verify the
"Bandwidth_int" value for your host.  Correct if it necessary.  The
value is the amount of bandwidth, in megabits per second, that your
server can serve Fedora content at.  The default value is "100",
meaning you can serve at 100 Mbits/sec.

If you had not listed a bandwidth value before, I set your value to
100.  If you had listed a value in the Bandwidth field before, it
_should_ be correct now, but please verify.


Tonight I deployed a slight update to MirrorManager that I'd been
wanting to do for a while.  The basic selection algorithm for choosing
the order in which to return mirrors to clients remains the same:
prefer same netblocks, internet2 in same country if on internet2, same
country, same continent, then global, in that order.  However, until
now, faster mirrors (those with larger bandwidths) were returned with
equal probability as slower mirrors.  This means not enough traffic
was being sent to our gigabit-connected mirrors, and too much traffic
was being sent to our slower mirrors.

The "Bandwidth_int" value is now used as a weight, and instead of
using python's random.shuffle() routine, I wrote a weighted_shuffle()
that behaves more like a raffle.  Mirrors with larger values of
'bandwidth_int' get more raffle tickets, thus a higher probability of
being returned earlier in the mirrorlist selection.  Slower mirrors
can still be returned as the first mirrorlist selection because this
is based on probabilities, but should not be overwhelmed anymore.

For those of you with 10Gbit connections, I've set your value to 1000
(1 gigabit) for now.  If after a few days you find you're really idle
and can handle more traffic, feel free to increase the value to 10000.

Thanks,
Matt
Fedora Mirror Wrangler

-- 
Matt Domsch
Linux Technology Strategist, Dell Office of the CTO
linux.dell.com & www.dell.com/linux

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