Package elki.logging

Logging facility for controlling logging behavior of the complete framework.

Logging in ELKI

Logging in ELKI is closely following the Logger approach.

However, system-wide configuration of logging does not seem appropriate, therefore ELKI uses a configuration file named

 logging -
living in the package elki.logging (or an appropriately named directory) for command line interface based operation.

Logging levels can be configured on a per-class or per-package level using, e.g.:

 elki.index.level = FINE
to set the logging level for the index structure package to FINE.

Logging for Developers:

Developers working in ELKI are encouraged to use the following setup to make configurable logging:
  1. Introduce one or multiple static final debug flags in their classes:
    protected static final boolean debug = true || LoggingConfiguration.DEBUG;
    After development, it should be changed to false || LoggingConfiguration.DEBUG.
  2. If the class contains 'frequent' logging code, acquire a static Logger reference:
    protected static final Logging logger = Logging.getLogger(Example.class);
  3. Wrap logging statements in appropriate level checks:
    if (logger.isVerbose()) { // compute logging message logger.verbose(expensive + message + construction); }
  4. For infrequent logging, the following static convenience function is appropriate: LoggingUtil.exception("Out of memory in algorithm.", exception);
    This function is expensive (it acquires a stack trace to obtain class and method references, retrieves a logger reference etc.) and thus should only be used for 'rare' logging events.
  5. In cases where many tests would occur, also consider using:
     final boolean verbose = logger.isVerbose();
     // ... for, while, anything expensive
     if (verbose) {