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Re: Challenge: Find potential use cases for non-trivial confinement

From: Pierre THIERRY
Subject: Re: Challenge: Find potential use cases for non-trivial confinement
Date: Tue, 2 May 2006 00:10:18 +0200
User-agent: Mutt/1.5.11+cvs20060403

Scribit Bas Wijnen dies 01/05/2006 hora 14:32:
> > For the same reason applied to the faculty or each student, the
> > program cannot run as an advertised service with CPU quota given
> > especially by the faculty or taken from the students collectively.
> This situation needs better system administration, not non-trivial
> confinement.

First, stop rejecting answers so fast with so few argumentation. That's
very annoying. If you know a precise better system administration scheme
that would fit my requirements for the use case, please expose it.

And if we accept that better sysadmin is a solution here, it is not an
``equivalent, alternative mechanism''. Please keep in mind my mail was
an answer to a very specific challenge. Please answer only WRT the

Using the sysadmin to address the problem here means allocating work
time from someone already quite busy, where there exist computational
mechanisms that lead to a (IMHO better) solution.

> These extra requirements are not realistic. The owner of the computer
> (the faculty) wants things to work. "We cannot touch the quota" is not
> a valid argument.

Using external CPU quotas here would be somewhat difficult[1], and
unfair. You could add a specific quota for the course, and run the
program as an advertised service on this quota. But if some students use
the master program more intensively than others, they could harm each
other. That would introduce a DoS vulnerability.

If you have an unfair student that doesn't like the others to succeed as
much or more than him, that's problematic. If you have stupid students
also. (that is, the hostile/buggy similarity also exists with humans)

With the Constructor pattern, none of these problems seems to arise.
Each student has access to the master program execution, no
administrative burden is put on anyone to achieve this, the conditions
decided by the teacher are met and students cannot harm each other.

If someone makes too much use of the master program, all that can happen
is that he will have to wait a long time for the various input data to
be processed.

Nowhere man
[1] if there is not much room to add quota for this specific course (it
would surely not be the only one needing such arrangements), it would be
necessary to reduce the overall quota of each student in the course to
allocate it to the serviceĀ ; in fact, this is even more unfair...
OpenPGP 0xD9D50D8A

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