NAME
    Log::Any::App - An easy way to use Log::Any in applications

VERSION
    version 0.34

SYNOPSIS
    Most of the time you only need to do this:

     # in your script.pl
     use Log::Any::App '$log';
     $log->warn("blah ...");
     if ($log->is_debug) { ... }

     # or, in command line
     % perl -MLog::Any::App -MModuleThatUsesLogAny -e'...'

    Here's the default logging that Log::Any::App sets up for you:

     Condition                        screen  file               syslog        dir
     --------------------------------+-------+------------------+-------------+---
     -e (one-liners)                  y       -                  -             -
     Scripts running as normal user   y       ~/NAME.log         -             -
     Scripts running as root          y       /var/log/NAME.log  -             -
     Daemons                          -       y                  y             -

    You can customize level from outside the script, using environment
    variables or command-line options (won't interfere with command-line
    processing modules like Getopt::Long etc):

     % DEBUG=1 script.pl
     % LOG_LEVEL=trace script.pl
     % script.pl --verbose

    And to customize other stuffs:

     use Log::Any::App '$log',
         -syslog => 1, # turn on syslog logging explicitly
         -screen => 0, # turn off screen logging explicitly
         -file   => {path=>'/foo/bar', max_size=>'10M', histories=>10};
                    # customize file logging

    For more customization like categories, per-category level, per-output
    level, multiple outputs, string patterns, etc see "USING AND EXAMPLES"
    and init().

DESCRIPTION
    Log::Any::App is a convenient combo for Log::Any and Log::Log4perl
    (although alternative backends beside Log4perl might be considered in
    the future). To use Log::Any::App you need to be sold on the idea of
    Log::Any first, so please do a read up on that first.

    The goal of Log::Any::App is to provide developers an easy and concise
    way to add logging to their **applications**. That is, instead of
    modules; modules remain using Log::Any to produce logs. Applications can
    upgrade to full Log4perl later when necessary, although in my
    experience, they usually don't.

    With Log::Any::App, you can replace this code in your application:

     use Log::Any '$log';
     use Log::Any::Adapter;
     use Log::Log4perl;
     my $log4perl_config = '
       some
       long
       multiline
       config...';
     Log::Log4perl->init(\$log4perl_config);
     Log::Any::Adapter->set('Log4perl');

    with just this:

     use Log::Any::App '$log'; # plus some other options when necessary

    Most of the time you don't need to configure anything as Log::Any::App
    will construct the most appropriate default Log4perl configuration for
    your application.

USING AND EXAMPLES
    To use Log::Any::App, just do:

     use Log::Any::App '$log';

    or from the command line:

     % perl -MLog::Any::App -MModuleThatUsesLogAny -e ...

    This will send logs to screen as well as file (unless -e scripts, which
    only log to screen). Default log file is ~/$SCRIPT_NAME.log, or
    /var/log/$SCRIPT_NAME.log if script is running as root. Default level is
    'warn'.

    The 'use Log::Any::App' statement can be issued before or after the
    modules that use Log::Any, it doesn't matter. Logging will be
    initialized in the INIT phase by Log::Any::App.

    You are not required to import '$log', and don't need to if you do not
    produce logs in your application (only in the modules).

  Changing logging level
    Since one of the most commonly tweaked logging setting is level (for
    example: increasing level when debugging problems), Log::Any::App
    provides several mechanisms to change log level, either from the script
    or from outside the script, for your convenience. Below are the
    mechanisms, ordered from highest priority:

    *   import argument (inside the script)

    *   command line arguments (outside the script)

    *   environment variables (outside the script)

    *   level flag files (outside the script)

    *   variables in 'main' package (inside the script)

    These mechanisms are explained in more details in the documentation for
    the init() function. But below are some examples.

    To change level from inside the script:

     use Log::Any::App '$log', -level => 'debug';

    This is useful if you want a fixed level that cannot be overriden by
    other mechanisms (since setting level using import argument has the
    highest priority). But oftentimes what you want is changing level
    without modifying the script itself. Thereby, just write:

     use Log::Any::App '$log';

    and then you can use environment variables to change level:

     TRACE=1 script.pl;         # setting level to trace
     DEBUG=1 script.pl;         # setting level to debug
     VERBOSE=1 script.pl;       # setting level to info
     QUIET=1 script.pl;         # setting level to error
     LOG_LEVEL=trace script.pl; # setting a specific log level

    or command-line options:

     script.pl --trace
     script.pl --debug
     script.pl --verbose
     script.pl --quiet
     script.pl --log_level=debug;   # '--log-level debug' will also do

    Regarding command-line options: Log::Any::App won't consume the
    command-line options from @ARGV and thus won't interfere with
    command-line processing modules like Getopt::Long or App::Options. If
    you use a command-line processing module and plan to use command-line
    options to set level, you might want to define these level options, or
    your command-line processing module will complain about unknown options.

  Changing default level
    The default log level is 'warn'. To change the default level, you can
    use 'main' package variables (since they have the lowest priority):

     use Log::Any::App '$log';
     BEGIN { our $Log_Level = 'info' } # be more verbose by default

    Then you will still be able to use level flag files or environment
    variables or command-line options to override this setting.

  Changing per-output level
    Logging level can also be specified on a per-output level. For example,
    if you want your script to be chatty on the screen but still logs to
    file at the default 'warn' level:

     SCREEN_VERBOSE=1 script.pl
     SCREEN_DEBUG=1 script.pl
     SCREEN_TRACE=1 script.pl
     SCREEN_LOG_LEVEL=info script.pl

     script.pl --screen_verbose
     script.pl --screen-debug
     script.pl --screen-trace=1
     script.pl --screen-log-level=info

    Similarly, to set only file level, use FILE_VERBOSE, FILE_LOG_LEVEL,
    --file-trace, and so on.

  Setting default per-output level
    As with setting default level, you can also set default level on a
    per-output basis:

     use Log::Any::App '$log';
     BEGIN {
         our $Screen_Log_Level = 'off';
         our $File_Quiet = 1; # setting file level to 'error'
         # and so on
     }

    If a per-output level is not specifed, it will default to the general
    log level.

  Enabling/disabling output
    To disable a certain output, you can do this:

     use Log::Any::App '$log', -file => 0;

    or:

     use Log::Any::App '$log', -screen => {level=>'off'};

    and this won't allow the output to be reenabled from outside the script.
    However if you do this:

     use Log::Any::App;
     BEGIN { our $Screen_Log_Level = 'off' }

    then by default screen logging is turned off but you will be able to
    override the screen log level using level flag files or environment
    variables or command-line options (SCREEN_DEBUG, --screen-verbose, and
    so on).

  Changing log level of cron scripts
    Environment variables and command-line options allow changing log level
    without modifying the script. But for scripts specified in crontab, they
    still require changing crontab entries, e.g.:

     # turn on debugging
     */5 * * * * DEBUG=1 foo

     # be silent
     */5 * * * * bar --quiet

    Another mechanism, level flag file, is useful in this case. By doing:

     $ echo debug > ~/foo.log_level
     # touch /etc/bar.QUIET

    you can also change log levels without modifying your crontab.

  Changing log file name/location
    By default Log::Any::App will log to file to ~/$NAME.log (or
    /var/log/$NAME.log if script is running as root), where $NAME is taken
    from the basename of $0. But this can be changed using:

     use Log::Any::App '$log', -name => 'myprog';

    Or, using custom path:

     use Log::Any::App '$log', -file => '/path/to/file';

  Changing other output parameters
    Each output argument can accept a hashref to specify various options.
    For example:

     use Log::Any::App '$log',
         -screen => {color=>0},   # never use color
         -file   => {path=>'/var/log/foo',
                     max_size=>'10M',
                     histories=>10,
                    },

    For all the available options of each output, see the init() function.

  Logging to syslog
    Logging to syslog is enabled by default if your script looks like or
    declare that it is a daemon, e.g.:

     use Net::Daemon; # this indicate your program is a daemon
     use Log::Any::App; # syslog logging will be turned on by default

     use Log::Any::App -daemon => 1; # script declares that it is a daemon

     # idem
     package main;
     our $IS_DAEMON = 1;

    But if you are certain you don't want syslog logging:

     use Log::Any::App -syslog => 0;

  Logging to directory
    This is done using Log::Dispatch::Dir where each log message is logged
    to a different file in a specified directory. By default logging to dir
    is not turned on, to turn it on:

     use Log::Any::App '$log', -dir => 1;

    For all the available options of directory output, see the init()
    function.

  Multiple outputs
    Each output argument can accept an arrayref to specify more than one
    output. For example below is a code to log to three files:

     use Log::Any::App '$log',
         -file => [1, # default, to ~/$NAME.log or /var/log/$NAME.log
                   "/var/log/log1",
                   {path=>"/var/log/debug_foo", category=>'Foo', level=>'debug'}];

  Changing level of a certain module
    Suppose you want to shut up logs from modules Foo, Bar::Baz, and Qux
    (and their submodules as well, e.g. Foo::Alpha, Bar::Baz::Beta::Gamma)
    because they are too noisy:

     use Log::Any::App '$log',
         -category_level => { Foo => 'off', 'Bar::Baz' => 'off', Qux => 'off' };

    or (same thing):

     use Log::Any::App '$log',
         -category_alias => { -noisy => [qw/Foo Bar::Baz Qux/] },
         -category_level => { -noisy => 'off' };

    You can even specify this on a per-output basis. Suppose you only want
    to shut up the noisy modules on the screen, but not on the file:

     use Log::Any::App '$log',
        -category_alias => { -noisy => [qw/Foo Bar::Baz Qux/] },
        -screen => { category_level => { -noisy => 'off' } };

    Or perhaps, you want to shut up the noisy modules everywhere, except on
    the screen:

     use Log::Any::App '$log',
         -category_alias => { -noisy => [qw/Foo Bar::Baz Qux/] },
         -category_level => { -noisy => 'off' },
         -syslog => 1,                        # uses general -category_level
         -file   => "/var/log/foo",           # uses general -category_level
         -screen => { category_level => {} }; # overrides general -category_level

  Preventing logging level to be changed from outside the script
    Sometimes, for security/audit reasons, you don't want to allow script
    caller to change logging level. As explained previously, you can use the
    'level' import argument (the highest priority of level-setting):

     use Log::Any::App '$log', -level => 'debug'; # always use debug level

    TODO: Allow something like 'debug+' to allow other mechanisms to
    *increase* the level but not decrease it. Or 'debug-' to allow other
    mechanisms to decrease level but not increase it. And finally
    'debug,trace' to specify allowable levels (is this necessary?)

  Debugging
    To see the Log4perl configuration that is generated by Log::Any::App and
    how it came to be, set environment LOGANYAPP_DEBUG to true.

FUNCTIONS
    None is exported.

  init(\@args)
    This is the actual function that implements the setup and configuration
    of logging. You normally need not call this function explicitly (but see
    below), it will be called once in an INIT block. In fact, when you do:

     use Log::Any::App 'a', 'b', 'c';

    it is actually passed as:

     init(['a', 'b', 'c']);

    You will need to call init() manually if you require Log::Any::App at
    runtime, in which case it is too late to run INIT block. If you want to
    run Log::Any::App in runtime phase, do this:

     require Log::Any::App;
     Log::Any::App::init(['a', 'b', 'c']);

    Arguments to init can be one or more of:

    -init => BOOL
        Whether to call Log::Log4perl->init() after setting up the Log4perl
        configuration. Default is true. You can set this to false, and you
        can initialize Log4perl yourself (but then there's not much point in
        using this module, right?)

    -name => STRING
        Change the program name. Default is taken from $0.

    -level_flag_paths => ARRAY OF STRING
        Edit level flag file locations. The default is [$homedir, "/etc"].

    -daemon => BOOL
        Declare that script is a daemon. Default is no. Aside from this, to
        declare that your script is a daemon you can also set
        $main::IS_DAEMON to true.

    -category_alias => {ALIAS=>CATEGORY, ...}
        Create category aliases so the ALIAS can be used in place of real
        categories in each output's category specification. For example,
        instead of doing this:

         init(
             -file   => [category=>[qw/Foo Bar Baz/], ...],
             -screen => [category=>[qw/Foo Bar Baz/]],
         );

        you can do this instead:

         init(
             -category_alias => {-fbb => [qw/Foo Bar Baz/]},
             -file   => [category=>'-fbb', ...],
             -screen => [category=>'-fbb', ...],
         );

    -category_level => {CATEGORY=>LEVEL, ...}
        Specify per-category level. Categories not mentioned on this will
        use the general level (-level). This can be used to increase or
        decrease logging on certain categories/modules.

    -level => 'trace'|'debug'|'info'|'warn'|'error'|'fatal'|'off'
        Specify log level for all outputs. Each output can override this
        value. The default log level is determined as follow:

        Search in command-line options. If App::Options is present, these
        keys are checked in %App::options: log_level, trace (if true then
        level is "trace"), debug (if true then level is "debug"), verbose
        (if true then level is "info"), quiet (if true then level is
        "error").

        Otherwise, it will try to scrape @ARGV for the presence of
        --log-level, --trace, --debug, --verbose, or --quiet (this usually
        works because Log::Any::App does this in the INIT phase, before you
        call Getopt::Long's GetOptions() or the like).

        Search in environment variables. Otherwise, it will look for
        environment variables: LOG_LEVEL, QUIET. VERBOSE, DEBUG, TRACE.

        Search in level flag files. Otherwise, it will look for existence of
        files with one of these names "$NAME.QUIET", "$NAME.VERBOSE",
        "$NAME.TRACE", "$NAME.DEBUG", or content of "$NAME.log_level" in ~
        or /etc.

        Search in main package variables. Otherwise, it will try to search
        for package variables in the "main" namespace with names like
        $Log_Level or $LOG_LEVEL or $log_level, $Quiet or $QUIET or $quiet,
        $Verbose or $VERBOSE or $verbose, $Trace or $TRACE or $trace, $Debug
        or $DEBUG or $debug.

        If everything fails, it defaults to 'warn'.

    -file => 0 | 1|yes|true | PATH | {opts} | [{opts}, ...]
        Specify output to one or more files, using
        Log::Dispatch::FileRotate.

        If the argument is a false boolean value, file logging will be
        turned off. If argument is a true value that matches
        /^(1|yes|true)$/i, file logging will be turned on with default path,
        etc. If the argument is another scalar value then it is assumed to
        be a path. If the argument is a hashref, then the keys of the
        hashref must be one of: "level", "path", "max_size" (maximum size
        before rotating, in bytes, 0 means unlimited or never rotate),
        "histories" (number of old files to keep, excluding the current
        file), "date_pattern" (will be passed to DatePattern argument in
        FileRotate's constructor), "tz" (will be passed to TZ argument in
        FileRotate's constructor), "category" (a string of ref to array of
        strings), "category_level" (a hashref, similar to -category_level),
        "pattern_style" (see "PATTERN STYLES"), "pattern" (Log4perl
        pattern).

        If the argument is an arrayref, it is assumed to be specifying
        multiple files, with each element of the array as a hashref.

        How Log::Any::App determines defaults for file logging:

        If program is a one-liner script specified using "perl -e", the
        default is no file logging. Otherwise file logging is turned on.

        If the program runs as root, the default path is
        "/var/log/$NAME.log", where $NAME is taken from $0 (or "-name").
        Otherwise the default path is ~/$NAME.log. Intermediate directories
        will be made with File::Path.

        If specified "path" ends with a slash (e.g. "/my/log/"), it is
        assumed to be a directory and the final file path is directory
        appended with $NAME.log.

        Default rotating behaviour is no rotate (max_size = 0).

        Default level for file is the same as the global level set by
        -level. But App::options, command line, environment, level flag
        file, and package variables in main are also searched first (for
        FILE_LOG_LEVEL, FILE_TRACE, FILE_DEBUG, FILE_VERBOSE, FILE_QUIET,
        and the similars).

    -dir => 0 | 1|yes|true | PATH | {opts} | [{opts}, ...]
        Log messages using Log::Dispatch::Dir. Each message is logged into
        separate files in the directory. Useful for dumping content (e.g.
        HTML, network dumps, or temporary results).

        If the argument is a false boolean value, dir logging will be turned
        off. If argument is a true value that matches /^(1|yes|true)$/i, dir
        logging will be turned on with defaults path, etc. If the argument
        is another scalar value then it is assumed to be a directory path.
        If the argument is a hashref, then the keys of the hashref must be
        one of: "level", "path", "max_size" (maximum total size of files
        before deleting older files, in bytes, 0 means unlimited), "max_age"
        (maximum age of files to keep, in seconds, undef means unlimited).
        "histories" (number of old files to keep, excluding the current
        file), "category", "category_level" (a hashref, similar to
        -category_level), "pattern_style" (see "PATTERN STYLES"), "pattern"
        (Log4perl pattern), "filename_pattern" (pattern of file name).

        If the argument is an arrayref, it is assumed to be specifying
        multiple directories, with each element of the array as a hashref.

        How Log::Any::App determines defaults for dir logging:

        Directory logging is by default turned off. You have to explicitly
        turn it on.

        If the program runs as root, the default path is "/var/log/$NAME/",
        where $NAME is taken from $0. Otherwise the default path is
        ~/log/$NAME/. Intermediate directories will be created with
        File::Path. Program name can be changed using "-name".

        Default rotating parameters are: histories=1000, max_size=0,
        max_age=undef.

        Default level for dir logging is the same as the global level set by
        -level. But App::options, command line, environment, level flag
        file, and package variables in main are also searched first (for
        DIR_LOG_LEVEL, DIR_TRACE, DIR_DEBUG, DIR_VERBOSE, DIR_QUIET, and the
        similars).

    -screen => 0 | 1|yes|true | {opts}
        Log messages using Log::Log4perl::Appender::ScreenColoredLevels.

        If the argument is a false boolean value, screen logging will be
        turned off. If argument is a true value that matches
        /^(1|yes|true)$/i, screen logging will be turned on with default
        settings. If the argument is a hashref, then the keys of the hashref
        must be one of: "color" (default is true, set to 0 to turn off
        color), "stderr" (default is true, set to 0 to log to stdout
        instead), "level", "category", "category_level" (a hashref, similar
        to -category_level), "pattern_style" (see "PATTERN STYLE"),
        "pattern" (Log4perl string pattern).

        How Log::Any::App determines defaults for screen logging:

        Screen logging is turned on by default.

        Default level for screen logging is the same as the global level set
        by -level. But App::options, command line, environment, level flag
        file, and package variables in main are also searched first (for
        SCREEN_LOG_LEVEL, SCREEN_TRACE, SCREEN_DEBUG, SCREEN_VERBOSE,
        SCREEN_QUIET, and the similars).

        Color can also be turned on/off using environment variable COLOR (if
        color argument is not set).

    -syslog => 0 | 1|yes|true | {opts}
        Log messages using Log::Dispatch::Syslog.

        If the argument is a false boolean value, syslog logging will be
        turned off. If argument is a true value that matches
        /^(1|yes|true)$/i, syslog logging will be turned on with default
        level, ident, etc. If the argument is a hashref, then the keys of
        the hashref must be one of: "level", "ident", "facility",
        "category", "category_level" (a hashref, similar to
        -category_level), "pattern_style" (see "PATTERN STYLES"), "pattern"
        (Log4perl pattern).

        How Log::Any::App determines defaults for syslog logging:

        If a program is a daemon (determined by detecting modules like
        Net::Server or Proc::PID::File, or by checking if -daemon or
        $main::IS_DAEMON is true) then syslog logging is turned on by
        default and facility is set to "daemon", otherwise the default is
        off.

        Ident is program's name by default ($0, or "-name").

        Default level for syslog logging is the same as the global level set
        by -level. But App::options, command line, environment, level flag
        file, and package variables in main are also searched first (for
        SYSLOG_LOG_LEVEL, SYSLOG_TRACE, SYSLOG_DEBUG, SYSLOG_VERBOSE,
        SYSLOG_QUIET, and the similars).

    -dump => BOOL
        If set to true then Log::Any::App will dump the generated Log4perl
        config. Useful for debugging the logging.

PATTERN STYLES
    Log::Any::App provides some styles for Log4perl patterns. You can
    specify "pattern_style" instead of directly specifying "pattern".
    example:

     use Log::Any::App -screen => {pattern_style=>"script_long"};

     Name           Description                        Example output
     ----           -----------                        --------------
     plain          The message, the whole message,    Message
                    and nothing but the message.
                    Used by dir logging.

                    Equivalent to pattern: '%m'

     script_short   For scripts that run for a short   [234] Message
                    time (a few seconds). Shows just
                    the number of milliseconds. This
                    is the default for screen.

                    Equivalent to pattern:
                    '[%r] %m%n'

     script_long    Scripts that will run for a        [2010-04-22 18:01:02] Message
                    while (more than a few seconds).
                    Shows date/time.

                    Equivalent to pattern:
                    '[%d] %m%n'

     daemon         For typical daemons. Shows PID     [pid 1234] [2010-04-22 18:01:02] Message
                    and date/time. This is the
                    default for file logging.

                    Equivalent to pattern:
                    '[pid %P] [%d] %m%n'

     syslog         Style suitable for syslog          [pid 1234] Message
                    logging.

                    Equivalent to pattern:
                    '[pid %p] %m'

    If you have a favorite pattern style, please do share them.

FAQ
  Why?
    I initially wrote Log::Any::App because I'm sick of having to parse
    command-line options to set log level like --verbose, --log-level=debug
    for every script. Also, before using Log::Any I previously used Log4perl
    directly and modules which produce logs using Log4perl cannot be
    directly use'd in one-liners without Log4perl complaining about
    uninitialized configuration or some such. Thus, I like Log::Any's
    default null adapter and want to settle using Log::Any for any kind of
    logging. Log::Any::App makes it easy to output Log::Any logs in your
    scripts and even one-liners.

  What's the benefit of using Log::Any::App?
    You get all the benefits of Log::Any, as what Log::Any::App does is just
    wrap Log::Any and Log4perl with some nice defaults. It provides you with
    an easy way to consume Log::Any logs and customize level/some other
    options via various ways.

  And what's the benefit of using Log::Any?
    This is better described in the Log::Any documentation itself, but in
    short: Log::Any frees your module users to use whatever logging
    framework they want. It increases the reusability of your modules.

  Do I need Log::Any::App if I am writing modules?
    No, if you write modules just use Log::Any.

  Why use Log4perl?
    Log::Any::App uses the Log4perl adapter to display the logs because it
    is mature, flexible, featureful. The other alternative adapter is
    Log::Dispatch, but you can use Log::Dispatch::* output modules in
    Log4perl and (currently) not vice versa.

    Other adapters might be considered in the future, for now I'm fairly
    satisfied with Log4perl. It does have a slightly heavy startup cost for
    my taste, but it is still bearable.

  Are you coupling adapter with Log::Any (thus defeating Log::Any's purpose)?
    No, producing logs are still done with Log::Any as usual and not tied to
    Log4perl in any way. Your modules, as explained above, only 'use
    Log::Any' and do not depend on Log::Any::App at all.

    Should portions of your application code get refactored into modules
    later, you don't need to change the logging part. And if your
    application becomes more complex and Log::Any::App doesn't suffice your
    custom logging needs anymore, you can just replace 'use Log::Any::App'
    line with something more adequate.

  How do I create extra logger objects?
    The usual way as with Log::Any:

     my $other_log = Log::Any->get_logger(category => $category);

  My needs are not met by the simple configuration system of Log::Any::App!
    You can use the Log4perl adapter directly and write your own Log4perl
    configuration (or even other adapters). Log::Any::App is meant for quick
    and simple logging output needs anyway (but do tell me if your logging
    output needs are reasonably simple and should be supported by
    Log::Any::App).

BUGS/TODOS
    Need to provide appropriate defaults for Windows/other OS.

    Probably: SCREEN0_DEBUG, --file1-log-level, etc.

SEE ALSO
    Log::Any and Log::Log4perl

    Some alternative logging modules: Log::Dispatchouli (based on
    Log::Dispatch), Log::Fast, Log::Log4perl::Tiny. Really, there are 7,451
    of them (roughly one third of CPAN) at the time of this writing.

AUTHOR
    Steven Haryanto <stevenharyanto@gmail.com>

COPYRIGHT AND LICENSE
    This software is copyright (c) 2011 by Steven Haryanto.

    This is free software; you can redistribute it and/or modify it under
    the same terms as the Perl 5 programming language system itself.

