Re: Timeout::Error

On Thu, 7 Feb 2008 09:37:57 +0900, Kurt Stephens <[e-mail]> wrote:
>   We use Timeout frequently for computations that we explicitly want to
> stop after a specific amount of time; we have hard timing constraints.
> If we can't compute it in time, we need to decide on a different course
> of action.

How hard are your timing constraints?  Remember that the delivery
of Thread#kill is not necessarily instantaneous, depending on how other
threads are scheduled.  Would it be feasible to check a flag or an
elapsed time during the computation itself?
 
> The only thing that is "exceptional" about Timeout errors is the
> delivery mechanism.

It's the delivery mechanism that's the basic problem; in a language
with side-effects (like Ruby), it is seldom possible to write code that
is entirely robust against asynchronous exceptions, and worse, most of
Ruby stdlib is not robust against them, so you must avoid any stdlib
code except simple blocking calls.

Given that, as long as none of the mutable objects modified by your
aborted computation persist past the timeout, you are okay, but that
is more difficult to achieve than you might naively expect.

-mental