[Melbourne-pm] Finding "Out of memory!"

[Mathew Robertson]

The Perl script should exit with a non-zero exit code... it doesn't really
matter why that exit code was non-zero, as any non-zero value will indicate
a failure mode.

eg: grep returns non-zero when it didn't actually grep for anything....
(you asked it to do something, but it couldn't).

Tracing STDERR will be fraught with problems - how do you know some Perl
library doesn't randomly spit out messages that you have yet to see?


just my $0.02,

Mathew


On 10 October 2014 10:46, Bradley Dean <bjdean at bjdean.id.au> wrote:

> Yes - that's certainly a safer approach. In fact I've found that what
> worked for me in my example code was version sensitive.
>
> On the system I started with the last system call was an mmap2 with a
> ENOMEM error and this is what I found when checking $!. I then tested
> this on a different system and discovered that after the mmap2 failed
> (and before my perl code had a chance to look at $!) a bunch of
> rt_sigaction systems calls happened and one of those failed with EINVAL
> so there was no ENOMEM to find.
>
> I feel there's a hack with a wrapper script which greps for "Out of
> memory!" on STDERR coming my way as the exit code doesn't tell me
> anything useful either.
>
> Cheerio,
>
>  Brad
>
> On Fri, Oct 10, 2014, at 10:37, Toby Wintermute wrote:
> > I really don't think this approach is going to pay dividends.
> > When you're hitting out of memory conditions in Perl, it's usually
> > game over. In some languages you could code up something that runs
> > without using any more memory, as a handler, but you don't have that
> > level of control in Perl.
> >
> > I'd look at wrapping your Perl script in another program - maybe just
> > a bash or even another Perl script - that waits for it to exit, and
> > then checks to see if it exited normally or with an error code.
> >
> > On 3 October 2014 11:54, Bradley Dean <bjdean at bjdean.id.au> wrote:
> > > Greetings folks,
> > >
> > > While looking at a problem where a variety of scripts might develop a
> > > memory leak and fatally terminate with "Out of memory!" I'm trying to
> > > work out if this seemingly simple code is in fact too simple:
> > >
> > > package NotifyOnOutOfMemory;
> > > use Errno;
> > > END {
> > >     # If the last errno indicates out of memory perl will now be
> > >     # terminating with "Out of memory!" so tell me about it.
> > >     if ( $! == Errno::ENOMEM ) {
> > >         # Do some low-memory thing that tells me a process has died due
> > >         to memory exhaustion
> > >         # eg. touch /path/to/some/file
> > >         #    or - exec("/path/to/script/which/emails/or/logs $$ $0
> > >         $someOtherDetail")
> > >      }
> > > }
> > > 1;
> > >
> > > Which would give me a drop in module for scripts with this problem.
> > >
> > > What am I missing? :)
> > >
> > > Cheerio,
> > >
> > >  Brad
> > >
> > > --
> > > Bradley Dean
> > > Email: bjdean at bjdean.id.au Skype: skype at bjdean.id.au
> > > Mobile(Aus): +61-413014395 WWW: http://bjdean.id.au/
> > > _______________________________________________
> > > Melbourne-pm mailing list
> > > Melbourne-pm at pm.org
> > > http://mail.pm.org/mailman/listinfo/melbourne-pm
> >
> >
> >
> > --
> > Turning and turning in the widening gyre
> > The falcon cannot hear the falconer
> > Things fall apart; the center cannot hold
> > Mere anarchy is loosed upon the world
>
>
> --
> Bradley Dean
> Email: bjdean at bjdean.id.au Skype: skype at bjdean.id.au
> Mobile(Aus): +61-413014395 WWW: http://bjdean.id.au/
> _______________________________________________
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>
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