David Dyer-Bennet writes:

> JuanE <[EMAIL PROTECTED]> writes on 2 August 2000 at 16:37:36 GMT
>  > 
>  > I agree with you both (Jay and Michael), at least partially. I agree that
>  > altough what Jay proposes will work, it is too much computation and that a
>  > simpler round-robin (after picking initial position) would suffice.
>  > 
>  > My comment is that in the event of a down server, the simple round robin
>  > will flood the next server in the chain with twice the load of the others.
>  > Jay's solution does not do this (at a high computational cost).
>  > 
>  > What I proposed earlier is just one of *many* solutions that addresses the
>  > flood problem at a lower computational cost.
>  > 
>  > Jay, I agree with you that selecting the same server many times in a row is
>  > not an issue. This is guaranteed by the Law of Averages (for you math
>  > wizzes out there, the Law of Large Numbers).
> Sounds like making repeated random picks is the way to go.  
> If no server is down, your one random pick will handle the mail (same
> cost as picking random starting point for round-robin).
> If a server is down *and you hit it*, you pay the cost of a second
> random pick.  This is slightly expensive, but you only pay it when
> you need it.  It's cheaper in elapsed time than trying the next server
> and having it refuse the connection due to overload, for example.  And
> it spreads the load more evenly.
> On the third hand, if the servers can manage their incoming
> connections intelligently (say with tcpserver :-) ), the one after a
> down one in a round-robin, while it will get hit a lot, can refuse
> some of the connections, which will then go on to the next after it.
> So you aren't really constrained to running all your servers at less
> than 50% capacity, and the one after the down one won't actually melt
> down. 
> -- 
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> David Dyer-Bennet / Welcome to the future! / [EMAIL PROTECTED]

I did not think of that. Good suggestion.

It seems like it would be a good compropmise if you can take your down
server out of the rotation relatively quickly. If not, then you'll waste
considerable time polling the busy server (and consequently having your
connections rejected by tcpserver) while all other servers are breezing at
50% load.


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