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Date:      Sun, 23 Jan 2000 18:56:39 -0700
From:      Warner Losh <imp@village.org>
To:        Brian Somers <brian@Awfulhak.org>
Cc:        current@FreeBSD.ORG
Subject:   Re: Please help spread the CVSup mirror load more evenly 
Message-ID:  <200001240156.SAA47712@harmony.village.org>
In-Reply-To: Your message of "Sun, 23 Jan 2000 13:03:19 GMT." <200001231303.NAA01359@hak.lan.Awfulhak.org> 
References:  <200001231303.NAA01359@hak.lan.Awfulhak.org>  

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In message <200001231303.NAA01359@hak.lan.Awfulhak.org> Brian Somers writes:
: I like this idea, except that some sort of consistency is required - 
: ie, once I've started using cvsupX, I'd like to use it in preference 
: to slightly better machines unless it stays bad for some configurable 
: number of connections....

I'm hatching in my head a scheme as follows:

Each host gets a value of 1 (unless you go in and tweak it).  Hosts
are tried in order of their values and in some unspecified order in
the case of ties.  Host with a value < = 0 are never tried.  Floating
point math is done with the results rounded up to the nearest integer.
This keeps people from falling below 1.  Users can disable a host by
tweaking its value in the config file to be 0.

Each time you successfully connect, you get a bonus of B.
Each failure reduces the nubmer by x%.

I'm thinking that B should be on the order of 10-20 and x should be on 
the order of 10-20.

Try at most twice per host.

If all the hosts fail, try the best host in forever mode.  No updates
should happen here to weightings.  Not sure about this method in, say, 
a cron job...

That way, as a host succeeds, it will be tried more often first.  As a 
host fails, it will be tried less often.  Over time if host N goes
down, its weighting will decay relatively quickly and the next best
one will take up the slack....  I purposely chose a linear scale up,
and a non-linear scale down.

Of course  I don't have time to actually code this up.  And it also
strikes me as overkill.  I'm happy with the fixed order list that I
tweak as I notice things going bad...

Warner


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