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.