Log::Contextual(3pm) User Contributed Perl Documentation Log::Contextual(3pm)
NAME
Log::Contextual - Simple logging interface with a contextual log
SYNOPSIS
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":
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' };
DESCRIPTION
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.)
OPTIONS
-logger
When you import this module you may use "-logger" as a shortcut for set_logger, for example:
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;
-package_logger
The "-package_logger" import option is similar to the "-logger" import option except "-package_logger" sets the the logger for the current
package.
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.
-default_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.
Basically it sets the logger to be used if "set_logger" is never called; so
package My::Package;
use Log::Contextual::SimpleLogger;
use Log::Contextual qw( :log ),
-default_logger => Log::Contextual::WarnLogger->new({
env_prefix => 'MY_PACKAGE'
});
A WORK IN PROGRESS
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.
FUNCTIONS
set_logger
my $logger = WarnLogger->new;
set_logger $logger;
Arguments: "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.
with_logger
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"
"with_logger" sets the logger for the scope of the "CodeRef" $to_execute. As with "set_logger", "with_logger" will wrap $returning_logger
with a "CodeRef" if needed.
log_$level
Import Tag: ":log"
Arguments: "CodeRef $returning_message, @args"
All of the following six functions work the same except that a different method is called on the underlying $logger object. The basic
pattern is:
sub log_$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
log_trace { 'entered method foo with args ' join q{,}, @args };
log_debug
log_debug { 'entered method foo' };
log_info
log_info { 'started process foo' };
log_warn
log_warn { 'possible misconfiguration at line 10' };
log_error
log_error { 'non-numeric user input!' };
log_fatal
log_fatal { '1 is never equal to 0!' };
logS_$level
Import Tag: ":log"
Arguments: "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_$level".
Dlog_$level
Import Tag: ":dlog"
Arguments: "CodeRef $returning_message, @args"
All of the following six functions work the same as their "log_$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, $frew->names->all;
and the output might look something like:
names: "fREW"
"fRIOUX"
"fROOH"
"fRUE"
"fiSMBoC"
Dlog_trace
my ($foo, $bar) = Dlog_trace { "entered method foo with args: $_" } @_;
Dlog_debug
Dlog_debug { "random data structure: $_" } { foo => $bar };
Dlog_info
return Dlog_info { "html from method returned: $_" } "<html>...</html>";
Dlog_warn
Dlog_warn { "probably invalid value: $_" } $foo;
Dlog_error
Dlog_error { "non-numeric user input! ($_)" } $port;
Dlog_fatal
Dlog_fatal { '1 is never equal to 0!' } 'ZOMG ZOMG' if 1 == 0;
DlogS_$level
Import Tag: ":dlog"
Arguments: "CodeRef $returning_message, Item $arg"
Like "logS_$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
my $pals_rs = DlogS_debug { "pals resultset: $_" }
$schema->resultset('Pals')->search({ perlers => 1 });
LOGGER INTERFACE
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.
AUTHOR
frew - Arthur Axel "fREW" Schmidt <frioux@gmail.com>
DESIGNER
mst - Matt S. Trout <mst@shadowcat.co.uk>
COPYRIGHT
Copyright (c) 2010 the Log::Contextual "AUTHOR" and "DESIGNER" as listed above.
LICENSE
This library is free software and may be distributed under the same terms as Perl 5 itself.
perl v5.10.1 2010-07-31 Log::Contextual(3pm)