Log::Log4perl::MDC - Mapped Diagnostic Context
Log::Log4perl allows loggers to maintain global thread-specific data, called the Nested Diagnostic Context (NDC) and Mapped Diagnostic Context (MDC).
The MDC is a simple thread-specific hash table, in which the application can stuff values under certain keys and retrieve them later via the "%X{key}" placeholder in Log::Log4perl::Layout::PatternLayouts.
"%X{key}"
Log::Log4perl::Layout::PatternLayout
Store a value $value under key $key in the map.
$value
$key
Retrieve the content of the map under the specified key. Typically done by %X{key} in Log::Log4perl::Layout::PatternLayout. If no value exists to the given key, the string "[undef]" is being returned.
%X{key}
"[undef]"
Delete all entries from the map.
Returns a reference to the hash table.
Please note that all of the methods above are class methods, there's no instances of this class. Since the thread model in perl 5.8.0 is "no shared data unless explicetly requested" the data structures used are just global (and therefore thread-specific).
Mike Schilli, <log4perl@perlmeister.com>
To install Log::Log4perl, copy and paste the appropriate command in to your terminal.
cpanm
cpanm Log::Log4perl
CPAN shell
perl -MCPAN -e shell install Log::Log4perl
For more information on module installation, please visit the detailed CPAN module installation guide.