[RevServer tips] Spreading the load or why wise developers use asynchronous workflows

Andre Garzia andre at andregarzia.com
Thu Aug 5 17:12:33 CDT 2010


On Thu, Aug 5, 2010 at 6:36 PM, Jeff Massung <massung at gmail.com> wrote:

> On Thu, Aug 5, 2010 at 4:26 PM, Mark Wieder <mwieder at ahsoftware.net>
> wrote:
>
> > Andre-
> >
> > Wednesday, August 4, 2010, 2:27:19 PM, you wrote:
> >
> > > Let me tell you that I once did something like that by accident on my
> own
> > > test server. I had a recursive process that started spawning itself and
> > > would not quit... in the end I had to reboot the damn vps. Thats why
> > those
> > > limits are important
> >
> > Awww... I've brought down bigger systems than that. Next time we sit
> > down over a beer I'll tell you about the time I found out what the
> > nohup command does...
> >
>
>
> While we're bringing up old "war stories" and measuring lengths...
>
> I have a friend who works for Boeing. Just to give a little physics
> background, satellites are not in perfect orbit; they are continuously
> falling to the Earth and need course correcting every so often.
>
> This one particular satellite used a particular program to course correct
> and the thrust units were measured in thousands (2000, 3000, etc). A new
> hire who was working late got the call for a course correct went to the
> machine, typed in the appropriate thrust amount and which rockets and hit
> enter. Was prompted "are you sure?", hit yes, and bye-bye satellite.
> Un-beknowst to the new guy, the program implicitly did the multiplication
> of
> units for him (he was supposed to enter 2, 3, ...).
>
> Nothing like firing a few hundred million dollars out into space your first
> week on the job, eh? ;-)
>
> Jeff M.
>

Wow, I wish I could ballistically implant a satellite into my government
presidential palace...

Not counting the whole earth orbit thing, I have a similar story, while
being a rookie student at engineering, we were "stationed" at a robotics lab
as the university. We built a mechanical arm and hand that was supposed to
pick a cup of coffee from a table without spilling it and put it into our
robotic waiter (aka motorized skate board).

This was in 1998, we used old 486 and 386 for our spare parts, we did not
have enclosures for those machines, so they usually were naked motherboards
on our tables while we were DOING SCIENCE or something similar.

The arm control software was written in Pascal and for the servo control we
would pass an integer to a function and after a quick sum it would move the
little arm. One very wise guy wondered what would happen if he changed that
+ sign to a * sign... coffee ended up on top of the motherboard as the arm
made a complete turn and manage to hit its own video card with the cup...
not a million dollars loss but a waste of a 386 running minix...

I've learned on that day never ever fiddle with magic numbers in software...
and I was not the one doing the arm thing, I was just watching and exploding
coffeemakers trying to hook them to my serial port.

As they said: "Robotics is the art of combining physics, computer science,
mechanics and large amounts of money into a machine that will gather huge
amounts of information regarding its surroundings and then ignore it and
drive into a wall."



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