futile.logger (version 1.2.1)

futile.logger-package: A logging sub-system for futile

Description

This package implements a logging system inspired by log4j and tries to maintain conceptual consistency with the package. This also extends to the similarly derivative work log4cpp. 'futile.logger' implements the core functionality available in the log4j feature suite, including hierarchical loggers, custom appenders, custom layouts, multiple appenders per logger, and configurable thresholds. The interface tries also to maintain R idioms and thus is not an exact clone.

Details

ll{ Package: futile.logger Type: Package Version: 1.2.1 Date: 2012-02-05 License: LGPL-3 LazyLoad: yes } The basic concepts connected to 'futile.logger' include loggers, appenders, and layouts. Loggers are the high-level interface for calling logging operations. These loggers are scoped to a particular namespace, which in more traditional object-oriented languages typically mapped to the package namespace. In R, a similar convention can be employed, such that different packages scope their logging calls to enable other code to easily switch on and off the log messages. Loggers have a threshold associated to them, such that only messages at the same level or of greater severity are printed. Multiple appenders can be attached to a given logger, giving flexibility in how to route log messages. Appenders do the actual work of writing log messages to a writeable target, whether that is a console, a file, a URL, database, etc. When creating an appender, the implementation- specific options are passed to the appender at instantiation. Once an appender is added to the 'futile.logger' options space, the appender can be attached to any logger. Appenders can override the threshold defined in the logger, which provides more granular control to the logging process.

Layouts are responsible for formatting messages. This operation usually consists of adding the log level, a timestamp, plus some pretty-printing to make the log messages easy on the eyes.

An important part of loggers is that they are hierarchical in nature based on the namespace given to the logger, such that loggers will inherit properties of parent loggers up to the ROOT if no definition is found. In practice packages can define a logger hierarchy that will work in user libraries, assuming the ROOT logger is configured properly.

To use 'futile.logger', at a minimum, one layout, appender, and logger (ROOT) must be defined. A number of default configurations are provided in the package to get users started quickly, while also acting as examples for users needing more sophisticated logging.

See Also

config_logger, addAppender, addLayout, addLogger, getLogger

Examples

config_logger()
  mylogger <- getLogger()
  mylogger(DEBUG, "This won't print")
  mylogger(WARN, "This will print")
  
  logger.b <- getLogger('b')
  logger.b(WARN, "This inherits from the ROOT logger")