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RFC: A closure guard with overall usage statistics

by Dallaylaen (Pilgrim)
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?

  • Comment on RFC: A closure guard with overall usage statistics

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Re: RFC: A closure guard with overall usage statistics
by Dallaylaen (Pilgrim) 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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Front-paged by Arunbear
[choroba]: What about [metadoc:// Algorithm::Loops]?
[Corion]: choroba: Yeah, but handing off the request to Dancer,Plack, Mojolicious,LWP is easy once I have the data filled into some structure ;))
[choroba]: Algorithm::Loops
[Corion]: choroba: I'm using that to generate the permutations, but I don't know how the user can pass the intended values to my function in a sane way
[Corion]: I have a prototype that permutes the get_parameters, but the values used for the get parameters should be different from the values used for the headers and potentially for parts of the URL
[Corion]: But yes, in general, my approach will be "split the URL into another set of parameters, generate an array of allowed values for each parameter and then NestedLoops() over the set"
[choroba]: hmm... so you need something like bag from Test::Deep, but not for checking, but for generation
[Corion]: This has the dual use of easily requesting sequential URLs and also being suitable for testing
[Corion]: For testing, I want to skip all tests with the same value(s) once one test fails to cut down on the number of failing tests
[Corion]: choroba: Yes, in a way I

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