[Python-Dev] Sandboxing Python (original) (raw)

"Martin v. Löwis" martin at v.loewis.de
Mon Mar 5 00:16:29 CET 2012

Am 04.03.2012 23:53, schrieb Steven D'Aprano:

Armin Rigo wrote:

Hi Mark,

On Sun, Mar 4, 2012 at 18:34, Mark Shannon <mark at hotpy.org> wrote: You can't solve the too much time, without solving the halting problem, Not sure what you mean by that. It seems to me that it's particularly easy to do in a roughly portable way, with alarm() for example on all UNIXes. What time should you set the alarm for? How much time is enough before you decide that a piece of code is taking too long? The halting problem is not that you can't breaking out of an infinite loop, but that you can't in general decide when you are in an infinite loop. I think that Mark's point is that you can't, in general, tell when you are in a "too much time" attack (or bug) that needs to be broken out of rather than just a legitimately long calculation which will terminate if you wait just a little longer.

This is getting off-topic, but you can certainly solve the "too much time" problem without solving the halting problem.

The "too much time" problem typically has a subjective, local, application-specific specification. Therefore, the "too much time" problem is easily solved with timeouts. Too much is just too much, even if it would eventually complete with a useful result.

I'd say that a single request should not take more than 20 seconds, else it's too much. It must be less than 2 seconds for interactive use, and less than 1s if you get more than 100 requests per second. If these numbers sound arbitrary to you: they are. They are still useful to me.

Regards, Martin

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