Log::Agent::Logger - a logging interface
require Log::Agent::Logger; my $log = Log::Agent::Logger->make( -channel => $chan, -max_prio => 'info', -min_prio => 'emerg', ); $log->error("can't open file %s: $!", $file); $log->warning("can't open file: $!");
The Log::Agent::Logger class defines a generic interface for application logging. It must not be confused with the interface provided by Log::Agent, which is meant to be used by re-usable modules that do not wish to commit on a particular logging method, so that they remain true building blocks.
Log::Agent::Logger
By contrast, Log::Agent::Logger explicitely requests an object to be used, and that object must commit upon the logging channel to be used, at creation time.
Optionally, minimum and maximum priority levels may be defined (and changed dynamically) to limit the messages to effectively log, depending on the advertised priority. The standard syslog(3) priorities are used.
The following channels are available:
Those channels are documented in Log::Agent::Channel.
Future Log::Agent::Logger extension will extend the set of available channels.
The creation routine is called make and takes the following switches:
make
-caller
Request that caller information (relative to the ->log() call) be part of the log message. The given parameters are handed off to the creation routine of Log::Agent::Tag::Caller and are documented there.
Log::Agent::Tag::Caller
I usually say something like:
-caller => [ -display => '($sub/$line)', -postfix => 1 ]
which I find informative enough. On occasion, I found myself using more complex sequences. See Log::Agent::Tag::Caller.
-channel
This defines the Log::Agent::Channel to be used for logging. Please refer to Log::Agent::Channel for details, and in particular to get a list of pre-defined logging channels.
Log::Agent::Channel
-min_prio
Defines the minimum priority to be logged (included). Defaults to "emerg".
-max_prio
Defines the maximum priority to be logged (included). Defaults to "debug".
-priority
Request that message priority information be part of the log message. The given parameters are handed off to the creation routine of Log::Agent::Tag::Priority and are documented there.
Log::Agent::Tag::Priority
-priority => [ -display => '[$priority]' ]
which will display the whole priority name at the beginning of the messages, e.g. "[warning]" for a warn() or "[error]" for error(). See Log::Agent::Tag::Priority and Log::Agent::Priorities.
-tags
Log::Agent::Tag
Specifies user-defined tags to be added to each message. The objects given here must inherit from Log::Agent::Tag and conform to its interface. See Log::Agent::Tag for details.
At runtime, well after the creation of the logging object, it may be desirable to add (or remove) a user tag. Use the tags attribute to retrieve the tag list object and interact with it, as explained in Log::Agent::Tag_List.
tags
Each routine is documented to take a single string, but you may also supply a code reference as the first argument, followed by extra arguments. That routine will be called, along with the extra arguments, to generate the message to be logged. If that sounds crazy, think about the CPU time we save by NOT calling the routine. If nothing is returned by the routine, nothing is logged.
If more than one argument is given, and the first argument is not a code reference, then it is taken as a printf() format, and the remaining arguments are used to fill the various "%" placeholders in the format. The special "%m" placeholder does not make use of any extra argument and is replaced by a stringification of the error message contained in $!, aka errno.
errno
There is a logging routine defined for each syslog(3) priority, along with aliases for some of them. Here is an exhaustive table, sorted by decreasing priority.
Syslog Alias -------- --------- emerg emergency alert crit critical err error warning warn notice info debug
We shall document only one routine for a given level: for instance, we document warn but you could also use the standard warning to achieve exactly the same funciton.
warn
warning
emergency($str)
Log at the "emerg" level, usually just before panicing. Something terribly bad has been detected, and the program might crash soon after logging this.
alert($str)
Log at the "alert" level, to signal a problem requiring immediate attention. Usually, some functionality will be missing until the condition is fixed.
critical($str)
Log at the "crit" level, to signal a severe error that prevents fulfilling some activity.
error($str)
Log at the "err" level, to signal a regular error.
warn($str)
Log at the "warning" level, which is an indication that something unusual occurred.
notice($str)
Log at the "notice" level, indicating something that is fully handled by the applicaiton, but which is not the norm. A significant condition, as they say.
info($str)
Log at the "info" level, for their amusement.
debug($str)
Log at the "debug" level, to further confuse them.
close
This routine closes the channel. Further logging to the logger is permitted, but will be simply discarded without notice.
The following access routines are defined:
channel
The defined logging channel. Cannot be changed.
max_prio
max_prio_str
Returns the maximum priority recorded, either as a numeric value or as a string. For the correspondance between the two, see Log::Agent::Priorities.
min_prio
min_prio_str
Returns the minimum priority recorded, either as a numeric value or as a string. For the correspondance between the two, see Log::Agent::Priorities.
set_caller_info
Dynamically change the caller information formatting in the logs. The list given supersedes the initial settings done via the -caller argument, if any, and is passed to the creation routine of the Log::Agent::Tag::Caller class. Note that a plain list must be given, not a list ref. An empty list removes caller information from subsequent logs.
Please see Log::Agent::Tag::Caller to get the allowed parameters for list.
set_max_prio($prio)
set_min_prio($prio)
Used to modify the maximum/minimum priorities. You can use either the string value or the numerical equivalent, as documented in Log::Agent::Priorities.
set_priority_info
Dynamically change the priority information formatting in the logs. The list given supersedes the initial settings done via the -priority argument, if any, and is passed to the creation routine of the Log::Agent::Tag::Priority class. Note that a plain list must be given, not a list ref. An empty list removes priority information from subsequent logs.
Please see Log::Agent::Tag::Priority to get the allowed parameters for list.
Returns a Log::Agent::Tag_List object, which holds all user-defined tags that are to be added to each log message.
Log::Agent::Tag_List
The initial list of tags is normally supplied by the application at creation time, via the -tags argument. See Log::Agent::Tag_List for the operations that can be performed on that object.
Raphael Manfredi <Raphael_Manfredi@pobox.com>
Test suite updated for Cygwin by Terrence Brannon, <tbone@cpan.org<gt>
Log::Agent::Channel(3).
To install Log::Agent::Logger, copy and paste the appropriate command in to your terminal.
cpanm
cpanm Log::Agent::Logger
CPAN shell
perl -MCPAN -e shell install Log::Agent::Logger
For more information on module installation, please visit the detailed CPAN module installation guide.