On Sep 16, 11:39 am, Stuart Halloway <stuart.hallo...@gmail.com>
wrote:
> The docs could be more clear, but if validate-fn must be side effect
> free then it certainly can't look at any other refs.
>
Yes. The docs should say the function must be pure. While I understand
the multi-ref validation use case, currently it is not supported.
Rich
>
> > On Sep 16, 11:15 am, Christophe Grand <christo...@cgrand.net> wrote:
> >> I think you managed to produce a deadlock :-(
>
> >> thread 1 is commiting and has a write lock on a1
> >> thread 2 is commiting and has a write lock on a2
> >> thread1 tries to acquire a read lock on a2 (in the validator) and
> >> blocks
> >> because thread2 has a write lock on a2.
> >> thread2 tries to acquire a read lock on a1 (in the validator) and
> >> blocks
> >> because thread1 has a write lock on a1.
>
> > Right, my first thought was a loop; but from your analysis, it is
> > obviously a deadlock.
>
> > I guess the conclusion is that you should not use validators for
> > inter-
> > ref validations. However, the documentation simply says:
>
> > "... validate-fn must be nil or a side-effect-free fn of one
> > argument, which will be passed the intended new state on any state
> > change. If the new state is unacceptable, the validate-fn should
> > return false or throw an exception. validate-fn will be called on
> > transaction commit, when all refs have their final values."
>
> > The last sentence seems to indicate that it is OK to look at several
> > refs.
>
> > So, yes, we need Rich here ;-)
>
> > /Karl
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