agent::tag(3)
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 sin gle 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 tar get of another tag insertion.
- The reality is a little bit more complex, to allow succes
sive 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 archi
tecturally defined to refer to
"Log::Agent::Tag::Caller" and "Log::Agent::Tag::Prior
ity" 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 withing the "Log::Agent::Message" mes_
sage, 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 call
back, 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>