[Cake] A few puzzling Cake results

[Toke Høiland-Jørgensen]

Jonathan Morton <chromatix99 at gmail.com> writes:

>> This is why I think that any fix that tries to solve this problem in
>> the queueing system should be avoided. It does not solve the real
>> problem (overload) and introduces latency.
>
> Most people, myself included, prefer systems that degrade gracefully
> instead of simply failing or rejecting new loads. Systems that exhibit
> the latter behaviours tend to be open to DoS attacks, which are
> obviously bad. Or users obsessively retry the failed requests until
> they succeed, increasing total load for the same goodput and inferior
> perceived QoS. Or ignorant application developers try to work around a
> perceived-unreliable system by spamming it with connections so that
> *their* traffic ends up getting through somehow.
>
> By designing a system which exhibits engineering elegance where
> practical, and graceful degradation otherwise, I try to encourage
> others to do the Right Thing by providing suitable incentives in the
> system's behaviour. The conventional way (of just throwing up one's
> hands when load exceeds capacity) has already been tried, extensively,
> and obviously doesn't work. Cake does better.

Except this is not simply a question of "better and more elegant". It is
a tradeoff between different concerns, and your solution significantly
hurts performance in the common case to accommodate a corner case that
quite fundamentally *can't* be solved properly at the queueing level, as
Luca points out.


-Toke