"Daniel L. Rall" wrote:
>
> Nissim wrote:
> >
> > The question is what do we lock to prevent two threads from (almost
> > simultaneously) creating the same object. We can lock the object which
> > is refreshing, to make sure no one touches it while it's refreshing, but
> > before an object is in the cache, there's nothing to lock. Would it
> > make sense to lock the whole cache while you build something to put in
> > there?
>
> Yes. The cache storage object should by synchronized whenever writes
> are being made to it.
But even if we synchronized the addObject method (which is probably a
good idea), that wouldn't prevent what Leon was talking about earlier.
If Contact number 7 is not in the cache, and two threads both try to get
it from the cache at nearly the same time, they'll both end up going to
the DB for it, with the slower one overwriting the one that the faster
one put in the cache first.
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