dustin at spy.net
Thu Jun 12 04:37:59 UTC 2008
On Jun 11, 2008, at 18:02, Grant Maxwell wrote:
> If the class is cached and the record exists then we allow the
> action to proceed.
> If the class is not cached then we just allow the action to proceed
> if the class is cached but the record does not exist then the
> action is denied.
Is there not a step like, ``if it's not cached, we need to look it
up?'' If not, then it seems like you want something more along the
lines of dynamo/chubby/zookeeper for these items.
The proposals that make sense to me around LRU policies are more for
QoS kinds of things. That is, you can rate something between ``this
is a little cheaper than recomputing it, but whatever'' to ``for the
love of [deity] do not uncache this before the expiration date.''
Even in the latter case, you must accept that the value *may* not be
where you think it is and will need to be recomputed.
The only time I really see making a business decision based on what
value is in the cache is if you're under a heavy load scenario and are
really trying to walk on eggshells around your centralized resource.
e.g. you might give an HTTP 503 kind of response, but definitely
nothing in the 400s.
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