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Digital Mages - Paranoid::Log(3)

Paranoid::Log

Section: User Contributed Perl Documentation (3)
Updated: 2020-12-31
Index  

NAME

Paranoid::Log - Log Functions  

VERSION

$Id: lib/Paranoid/Log.pm, 2.08 2020/12/31 12:10:06 acorliss Exp $  

SYNOPSIS

  use Paranoid::Log;

  $rv = startLogger($name, $mechanism, PL_WARN, PL_GE, { %options });
  $rv = stopLogger($name);

  $rv = plog($severity, $message);

 

DESCRIPTION

Paranoid::Log provides a logging and message distribution framework that's modeled heavily on syslog. It follows syslog in that it allows one to log messages at various levels of severity and have those messages distributed across multiple log mechanisms automatically. Within the Paranoid distribution itself it supports logging to files, STDERR, and named buffers. Additional modules exist on CPAN to allow for distribution to e-mail, syslog, and more. It is also relatively trivial to write your own log mechanism to work with this framework.  

IMPORT LISTS

This module exports the following symbols by default:

    PL_DEBUG PL_INFO PL_NOTICE PL_WARN PL_ERR PL_CRIT
    PL_ALERT PL_EMERG PL_EQ PL_NE PL_GE PL_LE
    startLogger stopLogger plog plverbosity

The following specialized import lists also exist:

    List        Members
    --------------------------------------------------------
    all         @defaults

 

LOGGING MECHANISMS

Each logging mechanism is implemented as separate module consisting of non-exported functions that conform to a a consistent API. Each mechanism module must have the following functions:

  Function        Description
  ------------------------------------------------------
  init            Called when module first loaded
  addLogger       Add a named instance of the mechanism
  delLogger       Removes a named instance of the mechanism
  logMsg          Logs the passed message

The init function is only called once --- the first time the module is used and accessed. No arguments are passed, and if unnecessary for a particular mechanism it can simply return a boolean true.

The logMsg function is used to actually pass a log message to the mechanism. It is called with a record hash based on the following template:

        my %record  = (
            name      => $name,
            mechanism => $name,
            msgtime   => time,
            severity  => $level,
            scope     => $scope,
            message   => $message,
            options   => {},
            );

The options key will be a hash reference to any logger-specific options, should the mechanism require one.

The addLogger function is called whenever a logger is started. It is called with the logger record above, minus a message and msgtime.

The delLogger function is called whenevever a logger is stopped. It is called with the logger record above, minus a message and msgtime.

Please see the source for Paranoid::Logger::File for a simple example of a mechanism module.  

SUBROUTINES/METHODS

 

startLogger

  $rv = startLogger($name, $mechanism, PL_WARN, PL_GE, { %options });

This function enables the specified logging mechanism at the specified levels. Each mechanism (or permutation of) is associated with an arbitrary name. This name can be used to bypass log distribution and log only in the named mechanism.

If you have your own custom mechanism that complies with the Paranoid::Log calling conventions you can pass this the name of the module (for example, MyLog::Foo).

Log levels are modeled after syslog:

  log level       description
  =====================================================
  PL_EMERG        system is unusable
  PL_ALERT        action must be taken immediately
  PL_CRIT         critical conditions
  PL_ERR          error conditions
  PL_WARN         warning conditions
  PL_NOTICE       normal but significant conditions
  PL_INFO         informational
  PL_DEBUG        debug-level messages

If omitted level defaults to PL_NOTICE.

Scope is defined with the following characters:

  character       definition
  =====================================================
  PL_EQ           log only messages at this severity
  PL_GE           log only messages at this severity
                    or higher
  PL_LE           log only messages at this severity
                    or lower
  PL_NE           log at all levels but this severity

If omitted scope defaults to PL_GE.

Only the first two arguments are mandatory. What you put into the %options, and whether you need it at all, will depend on the mechanism you're using. The facilities provided directly by Paranoid are as follows:

  mechanism        arguments
  =====================================================
  Stdout           none
  Stderr           none
  Buffer           bufferSize (optional)
  File             file, mode (optional), perm (optional),
                   syslog (optional)
  PDebug           none

 

stopLogger

  $rv = stopLogger($name);

Removes the specified logging mechanism from the configuration and re-initializes the distribution processor.  

plog

  $rv = plog($severity, $message);

  # If the PDebug mechanism is enabled
  $rv = plog($severity, $message, @substitutions);

This call logs the passed message to all facilities enabled at the specified log level. If you have PDebug enabled as a mechanism this function can also provide an equivalent sprintf functionality using the additional arguments, and that processed output will be shared with all other mechanisms that are enabled.

NOTE: PDebug support is meant to be a convenience to unify both normal logging and the Paranoid::Debug::pdebug STDERR tracing mechanism. That said, note than enabling it means that all log messages are passed to pdebug, since it has its own mechanism for deciding what gets sent to STDERR or not.

PDebug support may not make sense for if your logging and debug output can't be neatly lined up with the syslog-styled severities.  

plverbosity

    $rv = plverbosity($level);

This function provides a simpler way to enable Stdout/Stderr logging to the appropriate level, if you consider PL_DEBUG to PL_NOTICE to be normal operation messages appropriate for STDOUT messages, and PL_WARN through PL_EMERG to be error messages appropriate for STDERR.

This is primarily a convenience function for those simple, non-interactive programs/functions that need support varying levels of verbosity for the console. From that perspective, it will be assumed that all user notifications would be simple one-line messages.

NOTE: PL_EMERG and PL_ALERT are always enabled if you use this function. Any error messages that should always be printed to the console regardless of verbosity settings should be sent to one of those two levels. The remaining levels (PL_WARN through PL_CRIT) will be optionally enabled, just like PL_DEBUG> through PL_NOTICE.  

DEPENDENCIES

o
Paranoid::Debug
o
Paranoid::Input
o
Paranoid::Module
 

EXAMPLES

The following example provides the following behavior: debug messages go to a file, notice & above messages go to syslog, and critical and higher messages also go to console and e-mail.

  # Set up the logging facilities
  startLogger("debug-log", "File", PL_DEBUG, PL_GE,
    { file => '/var/log/myapp-debug.log' });
  startLogger("console-err", "Stderr", PL_CRIT, PL_GE);

  # This goes only to the debug log
  plog(PL_DEBUG, "Starting application");

  # Again, only the debug log
  plog(PL_NOTICE, "Uh, something happened...");

  # This goes to STDERR and the debug log
  plog(PL_EMERG, "Ack! <choke... silence>");

 

SEE ALSO

o
Paranoid::Log::Buffer
o
Paranoid::Log::File
 

BUGS AND LIMITATIONS

 

AUTHOR

Arthur Corliss (corliss@digitalmages.com)  

LICENSE AND COPYRIGHT

This software is free software. Similar to Perl, you can redistribute it and/or modify it under the terms of either:

  a)     the GNU General Public License
         <https://www.gnu.org/licenses/gpl-1.0.html> as published by the 
         Free Software Foundation <http://www.fsf.org/>; either version 1
         <https://www.gnu.org/licenses/gpl-1.0.html>, or any later version
         <https://www.gnu.org/licenses/license-list.html#GNUGPL>, or
  b)     the Artistic License 2.0
         <https://opensource.org/licenses/Artistic-2.0>,

subject to the following additional term: No trademark rights to ``Paranoid'' have been or are conveyed under any of the above licenses. However, ``Paranoid'' may be used fairly to describe this unmodified software, in good faith, but not as a trademark.

(c) 2005 - 2020, Arthur Corliss (corliss@digitalmages.com) (tm) 2008 - 2020, Paranoid Inc. (www.paranoid.com)


 

Index

NAME
VERSION
SYNOPSIS
DESCRIPTION
IMPORT LISTS
LOGGING MECHANISMS
SUBROUTINES/METHODS
startLogger
stopLogger
plog
plverbosity
DEPENDENCIES
EXAMPLES
SEE ALSO
BUGS AND LIMITATIONS
AUTHOR
LICENSE AND COPYRIGHT