NAME

       Log::Agent::Tag - formats caller information

SYNOPSIS

        Intended to be inherited from

DESCRIPTION

       This class is meant to be inherited by all the classes implementing a log message tag.

       A message tag is a little string that is either appended or prepended to all log messages.

       For instance, and oversimplifying a bit, a tag meant to be prepended will be inserted in front of the
       current log message, separated by separator, which defaults to a single space:

          +------------+-----------+---------------------------------+
          | tag string | separator |      current log message        |
          +------------+-----------+---------------------------------+

       This operation is called tag insertion. The whole string then becomes the current log message, and can be
       the target of another tag insertion.

       The reality is a little bit more complex, to allow successive tags to be prepended or appended in the
       order they are specified, and not in reverse order as they would be if naively implemented.  See
       Log::Agent::Message for the exact semantics of append() and prepend() operations.

FEATURES

       This section documents the interface provided to heirs, in case you wish to implement your own tag class.

       _init(name, postfix, separator)
           Initialization  routine  that  should be called by all heirs during creation to initialize the common
           attributes.

       postfix
           When true, the tag is meant to be appended to the log message.  Otherwise, it is prepended.

       name
           The name of this tag.  It is meant to provide by-name access to tags, check whether a  given  tag  is
           recorded,  etc...   The  names  "caller"  and  "priority"  are  architecturally  defined  to refer to
           "Log::Agent::Tag::Caller" and "Log::Agent::Tag::Priority" objects.

           NOTE: Currently unused by any client code.

       separator
           The sperating string inserted between the tag and the log  message.   It  defaults  to  "  "  if  not
           specified, i.e. left to "undef" when calling _init().

       string()
           A deferred routine, to be implemented by heirs.

           Returns the tag string only, without the separator, since its exact placement depends on the value of
           the "postfix" attribute.

       insert(message)
           Insert  this  tag  within  the  "Log::Agent::Message"  message,  according  to the tag specifications
           (placement, separator).  Calls string() to produce the tag string.

           This routine is frozen and should not be redefined by heirs.

STANDARD TAGGING CLASSES

       Tagging classes define via their "string()" routine what is  the  string  to  be  used  as  a  tag.   The
       insertion  of  the  tag  within  the  log message is done via a frozen routine from the "Log::Agent::Tag"
       ancestor.

       The following classes are provided by "Log::Agent":

       "Log::Agent::Tag::Callback"
           The "string()" routine invokes a user-supplied callback, given as a "Callback" object.  You need  the
           Callback module from CPAN if you wish to use this class.

       "Log::Agent::Tag::Caller"
           Used internally to compute the caller and format it according to user specifications.

       "Log::Agent::Tag::Priority"
           Used internally to format message priorities and add them to the log messages.

       "Log::Agent::Tag::String"
           Defines  a  constant  tagging string that should be added in all the log messages, e.g. a web session
           ID.

AUTHOR

       Raphael Manfredi <Raphael_Manfredi@pobox.com>

SEE ALSO

       Log::Agent::Message(3).

perl v5.36.0                                       2022-10-15                                    Agent::Tag(3pm)