MOO-cows Mailing List Archive


Re: DB crasher

--- Rich Connamacher wrote:
>Tell the wizzes of that moo to upgrade to 1.7.9p2 or the latest 1.8.0, 

True, but there are quite a number of server hacks in there that prevent
the transition being easy.  The server, I believe, is back in the 1.7.8
stone age, but there is no way to tell as ;version() returns 
"2.2.3 (hacked)"!

>because that already has a builtin task number monitor that's much more 
>effecient than such a clock and won't have the problem of erroniously 
>killing processes, because it simply won't let anyone begin any new 
>processes over their task quota limit.  

This is indeed better, I was simply mentioning an alternate way of dealing
with the problem.

>Although it's their moo so it's 
>their call, running a clock like that is an _extremely_ messy band-aid 
>fix to an old problem that doesn't exist anymore.  What's worse, the 
>chance that the moo will crash and loose data since the last checkpoint, 
>or the 100% certainty that all processes will suddenly crash and almost 
>certainly loose data in one way or another?  I'd opt to simply let it crash.

Mosts tasks are trivial, any important tasks in progress will usually be
in such a way that eliminates the need for suspending.

>(Note that, if there really were a true fork bomb attack on that moo, 
>unless the clock cycles so frequently as to lag the entire moo, the fork 
>bomb could grow so fast that the clock will choke and die trying to 
>keep up..  If they don't believe me, tell them to give me a prog bit on 
>their moo and an okay to go ahead and crash it.  Whoever wrote it 
>must not understand exponential mathematics.)

I've only managed to slip one accidental fork bomb by it, and that was due
to several objects running verbs forked at 2 second intervals.  (d'oh!)

As for the clock dying trying to keep up, unless someone added pre-emptive
multi-tasking when I wasn't looking, the server can kill ~15,000 tasks per
suspend(0).  This ought to be enough to keep up with most fork bombs.

As for a prog bit, it is hard enough to get a prog bit there when you AREN'T
tring to crash the MOO . . .

I think the guy understood exponential math just fine, as your garden variety
fork bomb is stopped instantly.



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