focal (3) Paranoid::Log.3pm.gz
NAME
Paranoid::Log - Log Functions
VERSION
$Id: lib/Paranoid/Log.pm, 2.07 2019/01/30 18:25:27 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.
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.
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 licensed under the same terms as Perl, itself. Please see http://dev.perl.org/licenses/ for more information. (c) 2005 - 2017, Arthur Corliss (corliss@digitalmages.com)