Overview

Since revision 498 in the main branch PET employs a logging framework for configurable log output. Instead of controlling the logging output in the various conceptual modules of PET (like packing/unpacking, generics, lexical processing, parsing, etc.) with a single option (namely, the old -verbose option), the new logging framework allows you to set the verbosity level for each module separately. In addition, it allows you to specify a printer for this module and level, which will print the log message in a specific format. The logging configuration will be read from a configuration file.

Dependencies

Two incarnations of the logging framework are available in PET. The "simple logging" framework and the "extended logging" framework via Log4cpp. The configure script uses the extended logging framework if available. Otherwise the simple logging framework will be used, which has no further dependencies.

Logging Explained

Several loggers are defined in PET which correspond to various conceptual modules like packing/unpacking, generics, lexical processing, parsing, etc. Log messages belonging to these modules are sent to the corresponding loggers. The loggers are identified by the log categories. The possible log categories are:

The rootCategory is special. It is used to configure the root logger, which is the default for all other loggers, if they don't specify anything else.

The log levels determine whether a log message is printed by a logger or not. If the log level of the message has the same or a higher priority than the configured log level of the responsible logger, then the log message is printed. The possible log levels are (log levels with highest priority first):

The printers specify the output destination and layout of each log message, e.g. whether a log message ends with a newline or whether it is prefixed with a date string. The extended logging framework supplies several appenders which are responsible for the actual output of the logging message.

Configuration

Simple Logging Framework

The simple logging framework will look up the configuration file simplelog.properties in the directory of the loaded grammar. An example file is provided with the PET source code. Copy this file to your grammar directory and adapt it accordingly.

Each line in simplelog.properties specifies the log category, the log level and a printer, using the following syntax:

<category>=[<level>][,<printer>]

The log categories and levels are specified as listed above. The possible printers are:

They all print to the standard error stream, using different layouts for the message.

An example simplelog.properties may look like the following:

rootCategory=WARN, simple
logParse=DEBUG
logSyntax=, simplest

The first line sets the default log level to WARN and the default printer to simple. The following line sets the parse logger to log level DEBUG, keeping the default printer of the root logger. The last line specifies a printer for the syntax logger, keeping the default log level of the root logger.

Extended Logging Framework

The extended logging framework will look up the configuration file logging.properties in the directory of the loaded grammar. An example file is provided with the PET source code. Copy this file to your grammar directory and adapt it accordingly.

PetLogging (last edited 2011-10-08 21:12:15 by localhost)

(The DELPH-IN infrastructure is hosted at the University of Oslo)