# Log::Log4perl::NDC - phpMan

## NAME
    [Log::Log4perl::NDC] - Nested Diagnostic Context

## DESCRIPTION
    [Log::Log4perl] allows loggers to maintain global thread-specific data,
    called the Nested Diagnostic Context (NDC).

    At some point, the application might decide to push a piece of data onto
    the NDC stack, which other parts of the application might want to reuse.
    For example, at the beginning of a web request in a server, the
    application might decide to push the IP address of the client onto the
    stack to provide it for other loggers down the road without having to
    pass the data from function to function.

    The [Log::Log4perl::Layout::PatternLayout] class even provides the handy
    %x placeholder which is replaced by the blank-separated list of elements
    currently on the stack.

    This module maintains a simple stack which you can push data on to,
    query what's on top, pop it off again or delete the entire stack.

    Its purpose is to provide a thread-specific context which all
    [Log::Log4perl] loggers can refer to without the application having to
    pass around the context data between its functions.

    Since in 5.8.0 perl's threads don't share data only upon request, global
    data is by definition thread-specific.

    [Log::Log4perl::NDC]->push($text);
        Push an item onto the stack. If the stack grows beyond the defined
        limit ($[Log::Log4perl::NDC::MAX_SIZE]), just the topmost element will
        be replated.

        This is typically done when a context is entered.

    [Log::Log4perl::NDC]->pop();
        Discard the upmost element of the stack. This is typically done when
        a context is left.

    my $text = [Log::Log4perl::NDC]->get();
        Retrieve the content of the stack as a string of blank-separated
        values without disrupting the stack structure. Typically done by %x.
        If the stack is empty the value "[undef]" is being returned.

    [Log::Log4perl::NDC]->remove();
        Reset the stack, remove all items.

    Please note that all of the methods above are class methods, there's no
    instances of this class.

## LICENSE
    Copyright 2002-2013 by Mike Schilli <<m@perlmeister.com>> and Kevin Goess
    <<cpan@goess.org>>.

    This library is free software; you can redistribute it and/or modify it
    under the same terms as Perl itself.

## AUTHOR
    Please contribute patches to the project on Github:

        <http://github.com/mschilli/log4perl>

    Send bug reports or requests for enhancements to the authors via our

    MAILING LIST (questions, bug reports, suggestions/patches):
    <log4perl-devel@lists.sourceforge.net>

    Authors (please contact them via the list above, not directly): Mike
    Schilli <<m@perlmeister.com>>, Kevin Goess <<cpan@goess.org>>

    Contributors (in alphabetical order): Ateeq Altaf, Cory Bennett, Jens
    Berthold, Jeremy Bopp, Hutton Davidson, Chris R. Donnelly, Matisse
    Enzer, Hugh Esco, Anthony Foiani, James FitzGibbon, Carl Franks, Dennis
    Gregorovic, Andy Grundman, Paul Harrington, Alexander Hartmaier David
    Hull, Robert Jacobson, Jason Kohles, Jeff Macdonald, Markus Peter, Brett
    Rann, Peter Rabbitson, Erik Selberg, Aaron Straup Cope, Lars Thegler,
    David Viner, Mac Yang.