NAME
Log::Log4perl::Tiny - mimic Log::Log4perl in one single module
VERSION
version 1.2.2
SYNOPSIS
use Log::Log4perl::Tiny qw( :easy );
Log::Log4perl->easy_init({
file => '>>/var/log/something.log',
layout => '[%d] [%-5P:%-5p] %m%n',
level => $INFO,
});
WARN 'something weird happened';
INFO 'just doing it';
DEBUG 'this does not get printed at $INFO level';
# LOGLEVEL isn't in Log::Log4perl, but might come handy
LOGLEVEL($DEBUG); # enable debugging for small section
# otherwise, "get_logger()->level($DEBUG)", see below
DEBUG 'now this gets printed';
LOGLEVEL($INFO); # disable debugging again
DEBUG 'skipped, again';
DEBUG 'complex evaluation value:', sub {
# evaluation skipped if log level filters DEBUG out
};
# Object-oriented interface is available as well
my $logger = get_logger();
$logger->level($DEBUG); # enable debugging for small section
$logger->debug('whatever you want');
$logger->level($INFO); # disable debugging again
# All stealth loggers are available
LOGCONFESS 'I cannot accept this, for a whole stack of reasons!';
# Want to change layout?
$logger->layout('[%d %p] %m%n');
# or, equivalently
$logger->format('[%d %p] %m%n');
# Want to send the output somewhere else?
use IO::Handle;
open my $fh, '>>', '/path/to/new.log';
$fh->autoflush();
$logger->fh($fh);
# Want to handle the output message by yourself?
my @queue; # all log messages will be put here
$logger->fh(sub { push @queue, $_[0] });
DESCRIPTION
Yes... yet another logging module. Nothing particularly fancy nor
original, too, but a single-module implementation of the features I use
most from Log::Log4perl for quick things, namely:
* easy mode and stealth loggers (aka log functions "INFO", "WARN",
etc.);
* debug message filtering by log level;
* line formatting customisation;
* quick sending of messages to a log file.
There are many, many things that are not included; probably the most
notable one is the ability to provide a configuration file.
Why?
I have really nothing against Log::Log4perl, to the point that one of
the import options is to check whether Log::Log4perl is installed and
use it if possible. I just needed to crunch the plethora of modules down
to a single-file module, so that I can embed it easily in scripts I use
in machines where I want to reduce my impact as much as possible.
Log Levels
Log::Log4perl::Tiny implements all *standard* Log::Log4perl's log
levels, without the possibility to change them. The correspondent values
are available in the following variables (in order of increasing
severity or *importance*):
$TRACE
$DEBUG
$INFO
$WARN
$ERROR
$FATAL
The default log level is $INFO. In addition to the above, the following
levels are defined as well:
$OFF
also in Log::Log4perl, useful to turn off all logging except for
"ALWAYS"
$DEAD
not in Log::Log4perl, when the threshold log level is set to this
value every log is blocked (even when called from the "ALWAYS"
stealth logger).
You can import these variables using the ":levels" import facility, or
you can use the directly from the Log::Log4perl::Tiny namespace. They
are imported automatically if the ":easy" import option is specified.
Default Log Level
As of version 1.1.0 the default logging level is still $INFO like any
previous version, but it is possible to modify this value to $DEAD
through the ":dead_if_first" import key.
This import key is useful to load Log::Log4perl in modules that you want
to publish but where you don't want to force the end user to actually
use it. In other terms, if you do this:
package My::Module;
use Log::Log4perl::Tiny qw( :easy :dead_if_first );
you will import all the functionalities associated to ":easy" but will
silence the logger off *unless* somewhere else the module is loaded (and
imported) without this option. In this way:
* if the user of your module does *not* import Log::Log4perl::Tiny,
all log messages will be dropped (thanks to the log level set to
$DEAD)
* otherwise, if the user imports Log::Log4perl::Tiny without the
option, the log level will be set to the default value (unless it
has already been explicitly set somewhere else).
Easy Mode Overview
I love Log::Log4perl's easy mode because it lets you set up a
sophisticated logging infrastructure with just a few keystrokes:
use Log::Log4perl qw( :easy );
Log::Log4perl->easy_init({
file => '>>/var/log/something.log',
layout => '[%d] [%-5P:%-5p] %m%n',
level => $INFO,
});
INFO 'program started, yay!';
use Data::Dumper;
DEBUG 'Some stuff in main package', sub { Dumper(\%main::) };
If you want, you can replicate it with just a change in the first line:
use Log::Log4perl::Tiny qw( :easy );
Log::Log4perl->easy_init({
file => '>>/var/log/something.log',
layout => '[%d] [%-5P:%-5p] %m%n',
level => $INFO,
});
INFO 'program started, yay!';
use Data::Dumper;
DEBUG 'Some stuff in main package', sub { Dumper(\%main::) };
Well... yes, I'm invading the Log::Log4perl namespace in order to reduce
the needed changes as mush as possible. This is useful when I begin
using Log::Log4perl and then realise I want to make a single script with
all modules embedded. There is also another reason why I put
"easy_init()" in Log::Log4perl namespace:
use Log::Log4perl::Tiny qw( :full_or_fake :easy );
Log::Log4perl->easy_init({
file => '>>/var/log/something.log',
layout => '[%d] [%-5P:%-5p] %m%n',
level => $INFO,
});
INFO 'program started, yay!';
use Data::Dumper;
DEBUG 'Some stuff in main package', sub { Dumper(\%main::) };
With import option "full_or_fake", in fact, the module first tries to
load Log::Log4perl in the caller's namespace with the provided options
(except "full_or_fake", of course), returning immediately if it is
successful; otherwise, it tries to "fake" Log::Log4perl and installs its
own logging functions. In this way, if Log::Log4perl is available it
will be used, but you don't have to change anything if it isn't.
Easy mode tries to mimic what Log::Log4perl does, or at least the things
that (from a purely subjective point of view) are most useful:
"easy_init()" and *stealth loggers*.
"easy_init()"
Log::Log4perl::Tiny only supports three options from the big brother:
"level"
the log level threshold. Logs sent at a higher or equal priority
(i.e. at a more *important* level, or equal) will be printed out,
the others will be ignored. The default value is $INFO;
"file"
a file name where to send the log lines. For compatibility with
Log::Log4perl, a 2-arguments "open()" will be performed, which means
you can easily set the opening mode, e.g. ">>filename". The default
is to send logging messages to "STDERR";
"layout"
the log line layout (it can also be spelled "format", they are
synonims). The default value is the following:
[%d] [%5p] %m%n
which means *date in brackets, then log level in brackets always
using five chars, left-aligned, the log message and a newline*.
If you call "easy_init()" with a single unblessed scalar, it is
considered to be the "level" and it will be set accordingly. Otherwise,
you have to pass a hash ref with the keys above.
Stealth Loggers
Stealth loggers are functions that emit a log message at a given
severity; they are installed when ":easy" mode is turned on (see "Easy
Mode Overview").
They are named after the corresponding level:
"TRACE"
"DEBUG"
"INFO"
"WARN"
"ERROR"
"FATAL"
Additionally, you get the following logger functions (again, these are
in line with Log::Log4perl):
"ALWAYS"
emit log whatever the configured logging level, apart from $OFF that
disables all logging;
"LOGWARN"
emit log at "WARN" level, "warn()" and then exit;
"LOGDIE"
emit log at "FATAL" level, "die()" and then exit (if "die()" didn't
already exit);
"LOGEXIT"
emit log at "FATAL" level and then exit;
"LOGCARP"
emit log at "WARN" level and then call "Carp::carp()";
"LOGCLUCK"
emit log at "WARN" level and then call "Carp::cluck()";
"LOGCROAK"
emit log at "FATAL" level and then call "Carp::croak()";
"LOGCONFESS"
emit log at "FATAL" level and then call "Carp::confess()";
If you want to set the exit code for "LOGWARN" and "LOGEXIT" above (and
"LOGDIE" as well, in case "die()" does not exit by itself), you can go
"the Log::Log4perl way" and set $Log::Log4perl::LOGEXIT_CODE, or set a
code with "logexit_code()" - but you have to wait to read something
about the object-oriented interface before doing this!
There is also one additional stealth function that Log::Log4perl misses
but that I think is of the outmoste importance: "LOGLEVEL", to set the
log level threshold for printing. If you want to be 100% compatible with
Log::Log4perl, anyway, you should rather do the following:
get_logger()->level(...); # instead of LOGLEVEL(...)
This function does not get imported when you specify ":easy", anyway, so
you have to import it explicitly. This will help you remembering that
you are deviating from Log::Log4perl.
Emitting Logs
To emit a log, you can call any of the stealth logger functions or any
of the corresponding log methods. All the parameters that you pass are
sent to the output stream as they are, except code references that are
first evaluated. This lets you embed costly evaluations (e.g. generate
heavy dumps of variabls) inside subroutines, and avoid the cost of
evaluation in case the log is filtered out:
use Data::Dumper;
LOGLEVEL($INFO); # cut DEBUG and TRACE out
TRACE 'costly evaluation: ', sub { Dumper($heavy_object) };
# Dumper() is not actually called because DEBUG level is
# filtered out
If you use the "log()" method, the first parameter is the log level,
then the others are interpreted as described above.
Log Line Layout
The log line layout sets the contents of a log line. The layout is
configured as a "printf"-like string, with placeholder identifiers that
are modeled (with simplifications) after Log::Log4perl's ones:
%c Category of the logging event.
%C Fully qualified package (or class) name of the caller
%d Current date in yyyy/MM/dd hh:mm:ss format
%F File where the logging event occurred
%H Hostname
%l Fully qualified name of the calling method followed by the
callers source the file name and line number between
parentheses.
%L Line number within the file where the log statement was issued
%m The message to be logged
%M Method or function where the logging request was issued
%n Newline (OS-independent)
%p Priority of the logging event
%P pid of the current process
%r Number of milliseconds elapsed from program start to logging
event
%% A literal percent (%) sign
Notably, both %x (NDC) and %X (MDC) are missing. Moreover, the extended
specifier feature with additional info in braces (like %d{HH:mm}) is
missing, i.e. the structure of each specifier above is fixed. (Thanks to
"Log::Tiny" for the cool trick of how to handle the "printf"-like
string, which is probably mutuated from "Log::Log4perl" itself according
to the comments).
INTERFACE
You have two interfaces at your disposal, the functional one (with all
the stealth logger functions) and the object-oriented one (with explicit
actions upon a logger object). Choose your preferred option.
Functional Interface
The functional interface sports the following functions (imported
automatically when ":easy" is passed as import option except for
"LOGLEVEL"):
"TRACE"
"DEBUG"
"INFO"
"WARN"
"ERROR"
"FATAL"
stealth logger functions, each emits a log at the corresponding
level;
"ALWAYS"
emit log whatever the configured logging level (except $DEAD);
"LOGWARN"
emit log at "WARN" level, "warn()" and then exit;
"LOGDIE"
emit log at "FATAL" level, "die()" and then exit (if "die()" didn't
already exit);
"LOGEXIT"
emit log at "FATAL" level and then exit;
"LOGCARP"
emit log at "WARN" level and then call "Carp::carp()";
"LOGCLUCK"
emit log at "WARN" level and then call "Carp::cluck()";
"LOGCROAK"
emit log at "FATAL" level and then call "Carp::croak()";
"LOGCONFESS"
emit log at "FATAL" level and then call "Carp::confess()";
"LOGLEVEL"
(Not in Log::Log4perl) (Not imported with ":easy")
set the minimum log level for sending a log message to the output;
Object-Oriented Interface
The functional interface is actually based upon actions on a pre-defined
fixed instance of a "Log::Log4perl::Tiny" object, so you can do the same
with a logger object as well:
"get_logger"
this function gives you the pre-defined logger instance (i.e. the
same used by the stealth logger functions described above).
"new"
if for obscure reasons the default logger isn't what you want, you
can get a brand new object! The constructor accepts either a list of
key-values or a reference to a hash, supporting the following keys:
format
layout
file
level
see "easy_init()" and the methods below with the same name
fh see method "fh" below
The methods you can call upon the object mimic the functional interface,
but with lowercase method names:
"trace"
"debug"
"info"
"warn"
"error"
"fatal"
logging functions, each emits a log at the corresponding level;
"is_trace"
"is_debug"
"is_info"
"is_warn"
"is_error"
"is_fatal"
"isTraceEnabled"
"isDebugEnabled"
"isInfoEnabled"
"isWarnEnabled"
"isErrorEnabled"
"isFatalEnabled"
log level test functions, each returns the status of the
corresponding level;
"always"
emit log whatever the configured logging level;
"logwarn"
emit log at "WARN" level (if allowed) and "warn()" (always);
"logdie"
emit log at "FATAL" level, "die()" and then exit (if "die()" didn't
already exit);
"logexit"
emit log at "FATAL" level and then exit;
"logcarp"
emit log at "WARN" level and then call "Carp::carp()";
"logcluck"
emit log at "WARN" level and then call "Carp::cluck()";
"logcroak"
emit log at "FATAL" level and then call "Carp::croak()";
"logconfess"
emit log at "FATAL" level and then call "Carp::confess()";
The main logging function is actually the following:
"log"
the first parameter is the log level, the rest is the message to log
apart from references to subroutines that are first evaluated
Additionally, you have the following accessors:
"level"
get/set the minimum level for sending messages to the output stream.
By default the level is set to $INFO.
"fh"
get/set the output filehandle.
As an extention over Log::Log4perl, you can also set a reference to
a subroutine as a filehandle, in which case it will be called with
two parameters: the message that would be print and a reference to
the logger object that is calling the sub. For example, if you
simply want to collect the log messages without actually outputting
them anywhere, you can do this:
my @messages;
get_logger()->fh(sub {
my ($message, $logger) = @_;
push @messages, $message;
return;
});
By default this parameter is set to be equal to "STDERR".
"format"
"layout"
get/set the line formatting;
"logexit_code"
get/set the exit code to be used with "logexit()" (and "logdie()" as
well if "die()" doesn't exit).
DEPENDENCIES
None.
BUGS AND LIMITATIONS
No bugs have been reported.
Please report any bugs or feature requests through http://rt.cpan.org/
SEE ALSO
Log::Log4perl is one of the most useful modules I ever used, go check
it!
AUTHOR
Flavio Poletti <polettix@cpan.org>
COPYRIGHT AND LICENSE
Copyright (C) 2010 by Flavio Poletti <polettix@cpan.org>.
This module is free software. You can redistribute it and/or modify it
under the terms of the Artistic License 2.0.
This program is distributed in the hope that it will be useful, but
without any warranty; without even the implied warranty of
merchantability or fitness for a particular purpose.