[Pdx-pm] forking

[Michael Rasmussen]

Michael G Schwern wrote:
> Michael Rasmussen wrote:
> > Consider this code representation:
> > 
> > while( database_query ) {
> > 
> >   bunch of stuff
> > 
> >   if(my $pid = fork) {
> >      parent processing
> >   } else { # child stuff follows
> >      if( ! $test_target ) {
> >             print "WTF? No $test_target?\n";
> >             $ret = test_it($test_target);
> >             exit $ret;
> >      }
> >   }
> > }
> > 
> > At this point you may be chuckling, scratching your head, wiping beverages off the
> > monitor or ...
> 
> Or having no idea.  I give, what's the gag?

I thought you were kidding.  I was almost embarrassed to post it...

A re-write:

while( database_query ) {
    bunch of stuff
    if(my $pid = fork) {
        parent processing # so far so good
    } else { # child stuff follows
       if(! $test_target) {
          print "WTF? No $test_target?\n"; # should have a $test_target, something is wrong here
          $ret = test_it($test_target);    # no target? are you sure a test is a sane thing to do?
          exit $ret;                       # give a result and quit being childish
       } 
       # flow here if we have a target to test
    }  # how special, the child program flow now joins with the parent, real family togetherness
}  # loop up for another db query, parent activities, another fork ...

When I ran it the 
   first clue was DBI errors about attempts to write to a locked db, and I only write in two parent places
   second clue was the system load averages staying very low, .05, but the system became unresponsive
   third clue was I/O wait shot up to 90%+, while all other sysload items stayed low, including swap
   fourth clue was "ps -ef | grep perl | perl -nae 'print $F[1],$/;' | xargs -n 1 kill -9"
     (Solaris system) would kill lots of processes and at the end I'd have lots still running.
   fifth clue was it worked fine a few days ago, so I must have done something...

I believe this is called a fork bomb.

-- 
      Michael Rasmussen, Portland Oregon  
    Be appropriate && Follow your curiosity
          http://www.patch.com/words/ 
  The fortune cookie says:
Satire is tragedy plus time.
		-- Lenny Bruce