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RFC: A closure guard with overall usage statistics

by Dallaylaen (Hermit)
on Jan 22, 2013 at 19:55 UTC ( #1014777=perlmeditation: print w/replies, xml ) Need Help??

Not long ago I was hunting a memory leak in a long-running AnyEvent-based application. I thought it would be a great idea to put a special guard object into every closure, so that I could see them created and destroyed.

The interface was very simple:

    # in initial section
    use My::Stat::Guard;
    my $stat = My::Stat::Guard->new;

    # when running
    my $guard = $stat->guard;
    my $callback = sub { 
        $guard->finish("taken route 1"); 
        # now do useful stuff
    # ... do whatever I need and call $callback eventually

    # in diagnostic procedures started via external event
    my $data = $stat->get_stat;
    # now I have some useful numbers in %$data
    # total: 100
    # alive: 19
    # dead: 81
    # etc.

get_stat also shows data for finished callbacks that still float around, and unfinished ones that left scope (typically both mean something went wrong).

The module also allows (when used with want_time => 1 parameter to new) to display (very rough) statistical distribution of guard lifetimes (== total time to process request).

I have searched CPAN for such a module before rolling out my own, but haven't found anything except several Guard-like modules.

So my question is: does such a module exist, and if not, is there a demand for one?

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Re: RFC: A closure guard with overall usage statistics
by Dallaylaen (Hermit) on Jan 26, 2013 at 09:23 UTC

    I've released initial draft to github:

    Hope it's useful/promising enough to get some bug reports.

    UPDATE: The module was released as Guard::Stats on July 13, 2013. "s" at the end was added to avoid confusion with something related to stat() system call.

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[stevieb]: Damn... just wasted two hours wondering why num 23 wasn't setting bit 5 in a register. I was working on the decimal, but the register holds BCD numbers. Sigh.

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