Log::Contextual - Simple logging interface with a contextual log
use Log::Contextual qw( :log :dlog set_logger with_logger ); use Log::Contextual::SimpleLogger; use Log::Log4perl ':easy'; Log::Log4perl->easy_init($DEBUG); my $logger = Log::Log4perl->get_logger; set_logger $logger; log_debug { 'program started' }; sub foo { with_logger(Log::Contextual::SimpleLogger->new({ levels => [qw( trace debug )] }) => sub { log_trace { 'foo entered' }; my ($foo, $bar) = Dlog_trace { "params for foo: $_" } @_; # ... log_trace { 'foo left' }; }); } foo();
Beginning with version 1.008 Log::Dispatchouli also works out of the box with Log::Contextual:
Log::Contextual
use Log::Contextual qw( :log :dlog set_logger ); use Log::Dispatchouli; my $ld = Log::Dispatchouli->new({ ident => 'slrtbrfst', to_stderr => 1, debug => 1, }); set_logger $ld; log_debug { 'program started' };
This module is a simple interface to extensible logging. It is bundled with a really basic logger, Log::Contextual::SimpleLogger, but in general you should use a real logger instead of that. For something more serious but not overly complicated, try Log::Dispatchouli (see "SYNOPSIS" for example.)
When you import this module you may use -logger as a shortcut for set_logger, for example:
-logger
use Log::Contextual::SimpleLogger; use Log::Contextual qw( :dlog ), -logger => Log::Contextual::SimpleLogger->new({ levels => [qw( debug )] });
sometimes you might want to have the logger handy for other stuff, in which case you might try something like the following:
my $var_log; BEGIN { $var_log = VarLogger->new } use Log::Contextual qw( :dlog ), -logger => $var_log;
The -package_logger import option is similar to the -logger import option except -package_logger sets the the logger for the current package.
-package_logger
Unlike "-default_logger", -package_logger cannot be overridden with "set_logger".
package My::Package; use Log::Contextual::SimpleLogger; use Log::Contextual qw( :log ), -package_logger => Log::Contextual::WarnLogger->new({ env_prefix => 'MY_PACKAGE' });
If you are interested in using this package for a module you are putting on CPAN we recommend Log::Contextual::WarnLogger for your package logger.
The -default_logger import option is similar to the -logger import option except -default_logger sets the the default logger for the current package.
-default_logger
Basically it sets the logger to be used if set_logger is never called; so
set_logger
package My::Package; use Log::Contextual::SimpleLogger; use Log::Contextual qw( :log ), -default_logger => Log::Contextual::WarnLogger->new({ env_prefix => 'MY_PACKAGE' });
This module is certainly not complete, but we will not break the interface lightly, so I would say it's safe to use in production code. The main result from that at this point is that doing:
use Log::Contextual;
will die as we do not yet know what the defaults should be. If it turns out that nearly everyone uses the :log tag and :dlog is really rare, we'll probably make :log the default. But only time and usage will tell.
:log
:dlog
my $logger = WarnLogger->new; set_logger $logger;
Arguments: Ref|CodeRef $returning_logger
Ref|CodeRef $returning_logger
set_logger will just set the current logger to whatever you pass it. It expects a CodeRef, but if you pass it something else it will wrap it in a CodeRef for you. set_logger is really meant only to be called from a top-level script. To avoid foot-shooting the function will warn if you call it more than once.
CodeRef
my $logger = WarnLogger->new; with_logger $logger => sub { if (1 == 0) { log_fatal { 'Non Logical Universe Detected' }; } else { log_info { 'All is good' }; } };
Arguments: Ref|CodeRef $returning_logger, CodeRef $to_execute
Ref|CodeRef $returning_logger, CodeRef $to_execute
with_logger sets the logger for the scope of the CodeRef $to_execute. As with "set_logger", with_logger will wrap $returning_logger with a CodeRef if needed.
with_logger
$to_execute
$returning_logger
Import Tag: :log
Arguments: CodeRef $returning_message, @args
CodeRef $returning_message, @args
All of the following six functions work the same except that a different method is called on the underlying $logger object. The basic pattern is:
$logger
sub log_$level (&@) { if ($logger->is_$level) { $logger->$level(shift->(@_)); } @_ }
Note that the function returns it's arguments. This can be used in a number of ways, but often it's convenient just for partial inspection of passthrough data
my @friends = log_trace { 'friends list being generated, data from first friend: ' . Dumper($_[0]->TO_JSON) } generate_friend_list();
If you want complete inspection of passthrough data, take a look at the "Dlog_$level" functions.
log_trace { 'entered method foo with args ' join q{,}, @args };
log_debug { 'entered method foo' };
log_info { 'started process foo' };
log_warn { 'possible misconfiguration at line 10' };
log_error { 'non-numeric user input!' };
log_fatal { '1 is never equal to 0!' };
Arguments: CodeRef $returning_message, Item $arg
CodeRef $returning_message, Item $arg
This is really just a special case of the "log_$level" functions. It forces scalar context when that is what you need. Other than that it works exactly same:
my $friend = logS_trace { 'I only have one friend: ' . Dumper($_[0]->TO_JSON) } friend();
See also: "DlogS_$level".
Import Tag: :dlog
All of the following six functions work the same as their "log_$level" brethren, except they return what is passed into them and put the stringified (with Data::Dumper::Concise) version of their args into $_. This means you can do cool things like the following:
$_
my @nicks = Dlog_debug { "names: $_" } map $_->value, $frew->names->all;
and the output might look something like:
names: "fREW" "fRIOUX" "fROOH" "fRUE" "fiSMBoC"
my ($foo, $bar) = Dlog_trace { "entered method foo with args: $_" } @_;
Dlog_debug { "random data structure: $_" } { foo => $bar };
return Dlog_info { "html from method returned: $_" } "<html>...</html>";
Dlog_warn { "probably invalid value: $_" } $foo;
Dlog_error { "non-numeric user input! ($_)" } $port;
Dlog_fatal { '1 is never equal to 0!' } 'ZOMG ZOMG' if 1 == 0;
Like "logS_$level", these functions are a special case of "Dlog_$level". They only take a single scalar after the $returning_message instead of slurping up (and also setting wantarray) all the @args
$returning_message
wantarray
@args
my $pals_rs = DlogS_debug { "pals resultset: $_" } $schema->resultset('Pals')->search({ perlers => 1 });
Because this module is ultimately pretty looking glue (glittery?) with the awesome benefit of the Contextual part, users will often want to make their favorite logger work with it. The following are the methods that should be implemented in the logger:
is_trace is_debug is_info is_warn is_error is_fatal trace debug info warn error fatal
The first six merely need to return true if that level is enabled. The latter six take the results of whatever the user returned from their coderef and log them. For a basic example see Log::Contextual::SimpleLogger.
frew - Arthur Axel "fREW" Schmidt <frioux@gmail.com>
mst - Matt S. Trout <mst@shadowcat.co.uk>
Copyright (c) 2010 the Log::Contextual "AUTHOR" and "DESIGNER" as listed above.
This library is free software and may be distributed under the same terms as Perl 5 itself.
To install Log::Contextual, copy and paste the appropriate command in to your terminal.
cpanm
cpanm Log::Contextual
CPAN shell
perl -MCPAN -e shell install Log::Contextual
For more information on module installation, please visit the detailed CPAN module installation guide.