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Log-OK-v0.2.1
River stage one • 3 direct dependents • 5 total dependents
/ Log::OK

NAME

Log::OK - Disable inactive logging statements from the command line

SYNOPSIS

Application

Choose your logging framework (Log::ger shown). (1)

Setup your adaptor/dispatchers/output like usual (2)

Then use Log::OK to setup a default logging level and/or specify a command line option (or environment variable) to set logging level. (3)

  # Top level application
        use Log::ger;                                 #(1)
        use Log::ger::Output "Screen";  #(2)

        use Log::OK {                                 #(3)
                lvl=>"info",            
                opt=>"verbose"          
        };


        My_Module::do_module_stuff();

Module

In your module, bring in your logging framework (Log::ger shown). (1)

Then bring in Log::OK, and optionally configure it with a default level. This will be used if the top level script didn't define one (2)

Constant names will be logging levels supported in your logging module, but converted to upper case.

Use a constant together with a logical "and" and your logging statement for perl to optimise away inactive levels. (3)

  # Module ...
        package My_Module;

        use Log::ger;   #(1)
        use Log::OK;    #(2)

        sub do_module_stuff {
                                #(3)

                Log::OK::FATAL and log_fatal("Fatal");
                Log::OK::ERROR and log_error("Error");
                Log::OK::WARN and log_warn("Warning");
                Log::OK::INFO and log_info("Information");
                Log::OK::DEBUG and log_debug("Debug");
                Log::OK::TRACE and log_trace("Trace");
        }

        1;

Run the program

The logging level and compile time constants are configured via the command line using the GetOpt::Long options specification used:

        perl my_app.pl --verbose error

The output of the above would be

        Fatal
        Error
        Warning
        Information

Notice, Debug and Trace logging will not be executed at runtime

DESCRIPTION

Log::OK creates compile time constants/flags for each level of logging supported by your selected logging framework. This module does not implement logging features, nor does it depend on any particular logger. It only generates constants to help enable/disable logging efficiently.

The logging modules supported are Log::Any, Log::ger, Log::Dispatch and Log::Log4perl. These systems can be autodetected if they are imported before Log::OK. The constants generated are named according to the detected modules logging levels.

For example, if your selected logging system was Log::ger, and the logging level was set to "info", the constants generated would be:

        Log::OK::FATAL  = 1;
        Log::OK::ERROR  = 1;
        Log::OK::WARN   = 1;
        Log::OK::INFO   = 1;
        Log::OK::DEBUG  = undef;
        Log::OK::TRACE  = undef;

The value of constants are determined from the logging level specified in code, from the command line (set or increment) or an environment variable of your choosing.

The idea is to have a logger independent method of completely disabling inactive logging statements to reduce runtime overhead.

By using the generated constants/flags in the following fashion, perl will optimise away this entire statement when Log::OK::DEBUG is false for example:

                Log::OK::DEBUG and log_DEBUG("This message is optimised away");

USAGE

The constants generated are determined by the logging system selected/detected at the point of the use Log::OK pragma. That means you need to bring in your logging framework before you bring in Log::OK:

  use Log::Any;           # <- Pick one
  use Log::ger;           # <-  
  use Log::Dispatch;      # <-
  use Log::Log4perl;      # <-

        use Log::OK {
                opt=>$get_opt_long_spec,
                env=>$env_var_name,
                lvl=>$defualt_level,
                sys=>$logging_system,
        };

Hash keys

All keys to the hash are optional and are detailed below:

lvl

This is the base logging level. It may be modified by a command line option, or environment variable. It must be a string representing a logging level in your chosen logging framework.

If this field is not supplied, then the lowest logging level in your selected logging module is set as the default (i.e Emergency, Trace...)

opt

Represents a GetOpt::Long option name to use in processing the command line options. It has a ":s" appended to it to allow GetOpt::Long to process just a switch or a switch with a value.

From v0.2.0: If not specified it defaults to "verbose". If you want no command line options procssing, explicitly set to undef.

For example if opt=>'verbose', (the default) the logging level will be set to "debug" with the following:

                perl my_app.pl --verbose debug

                        #or

                perl my_app.pl --v debug

If the switch only is used, each use will increment the logging level:

                #Increments the logging two levels above the default
                perl my_app.pl -v -v

                #Set the logging level to info and then increase to the next level
                perl my_app.pl -v info -v

If a invalid level is specified on the command line, a list of valid options is printed with a croak call

This is implemented using constant::more. Please refer to that module for more implementation details.

env

The name of the environment variable to use to set the logging level. For example setting to env=>'MY_VAR' the logging level could be set to "trace" with:

                MY_VAR=trace perl my_app.pl

This is implemented using constant::more. Please refer to that module for more implementation details.

sys

This informs Log::OK of the logging system in use instead of an attempting to detect it automatically. It is a string value of the package name of the logging system. For example to force constants that relate to Log::ger:

                sys=>"Log::ger"

Constant Naming

The names of the constants generated are specific to the logging system used and are installed in the Log::OK namespace. The names are the same as the logging levels, but are converted to uppercase the usual constant style. If the logging system has aliases to levels these are also used to generate constants

Import and Constant Definition Precedence

For autodetection to work, the logging framework (producer or consumer) should be imported before Log::OK

        use Log::Any;
        #configure log any

        use Log::OK {...}

Constants are only defined once in a first come first serve basis. So this means to override the logging levels of a required module, use Log::OK will need to appear before any modules that also use it:

        use Log::OK {..}

        use My::Fancy::Module; #module that uses Log::OK

Extracting Log Level

The log level used to create the constants is accessible via Log::OK::LEVEL. It is a string representation of the log level in the detected logging framework.

v0.1.4 and later If Log::ger is used, it has the log level synchronised automatically with:

      Log::ger::Util::set_level Log::OK::LEVEL;

Prior to v0.1.4 As Log::OK doesn't interfere with your logging setup. As such, if you would like to synchronise the levels in Log::OK and your logger, it will need to be set manually in your logger:

        #Log::Log4perl
        $logger->level(Log::OK::LEVEL);

  #Log:ger
  Log::ger::Util::set_level Log::OK::LEVEL;

This is sometimes necessary to avoid internal filtering of the log messages

Error Reporting

If the logging level attempting to be set is not supported by the logging system detected, croak is called with a list of supported level names

LIMITATIONS

Constants are treated as constants so, once they are defined, the value remains the same for the program duration.

Using multiple logging frameworks in the same project (sub modules choosing a different one that you for example) should work as long as:

  • You don't need to rely on Log::OK::LEVEL to synchronise the logging level. This value is framework specific.

  • Command line processing is only done by one module.

Also the incremental changing of the logging level from the command line only increases the logging level (no decrement).

Synchronising the logging level of your logging framework is easy in some and not so easy in others. If you are missing log messages the logger might be configured with a different logging level

REPOSITOTY and BUGS

Please report and feature requests or bugs via the github repo:

https://github.com/drclaw1394/perl-log-ok.git

AUTHOR

Ruben Westerberg, <drclaw@mac.com>

COPYRIGHT AND LICENSE

Copyright (C) 2023 by Ruben Westerberg

Licensed under MIT

DISCLAIMER OF WARRANTIES

THIS PACKAGE IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.