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"""General logging facility

This module attempts to provide a simple programming API for logging
with a pluggable API for defining where log messages should go.

Programmers call the LOG function to log information.

The LOG function, in turn, calls the log_write method to actually write
logging information somewhere.  This module provides a very simple
log_write implementation.  It is intended that applications main
programs will replace this method with a method more suited to their needs.

The module provides a register_subsystem method that does nothing, but
provides a hook that logging management systems could use to collect information about subsystems being used.

The module defines several standard severities:

  TRACE=-300   -- Trace messages

  DEBUG=-200   -- Debugging messages

  BLATHER=-100 -- Somebody shut this app up.

  INFO=0       -- For things like startup and shutdown.

  PROBLEM=100  -- This isn't causing any immediate problems, but deserves
                  attention.

  WARNING=100  -- A wishy-washy alias for PROBLEM.

  ERROR=200    -- This is going to have adverse effects.

  PANIC=300    -- We're dead!

Also, looging facilities will normally ignore negative severities.

To plug in a log handler, simply replace the log_write function
with a callable object that takes 5 arguments:


      subsystem -- The subsystem generating the message (e.g. ZODB)

      severity -- The "severity" of the event.  This may be an integer or
                  a floating point number.  Logging back ends may
                  consider the int() of this valua to be significant.
                  For example, a backend may consider any severity
                  whos integer value is WARNING to be a warning.

      summary -- A short summary of the event

      detail -- A detailed description

      error -- A three-element tuple consisting of an error type, value, and
               traceback.  If provided, then a summary of the error
               is added to the detail.

The callable object can provide a reinitialize method that may be
called with no arguments to reopen the log files (if any) as part of a
log-rotation facility.

There is a default event logging facility that:

  - swallows logging information by default,

  - outputs to sys.stderr if the environment variable
    EVENT_LOG_FILE is set to an empty string, and

  - outputs to file if the environment variable
    EVENT_LOG_FILE is set to a file name.

  - Ignores errors that have a severity < 0 by default. This
    can be overridden with the environment variable EVENT_LOG_SEVERITY

"""
__version__='$Revision: 1.8 $'[11:-2]

from MinimalLogger import log_write, log_time, severity_string, \
     _set_log_dest, initialize
from FormatException import format_exception

# Standard severities
TRACE   = -300
DEBUG   = -200
BLATHER = -100
INFO    =    0
PROBLEM =  100
WARNING =  100
ERROR   =  200
PANIC   =  300

def LOG(subsystem, severity, summary, detail='', error=None, reraise=None):
    """Log some information

    The required arguments are:

      subsystem -- The subsystem generating the message (e.g. ZODB)

      severity -- The "severity" of the event.  This may be an integer or
                  a floating point number.  Logging back ends may
                  consider the int() of this valua to be significant.
                  For example, a backend may consider any severity
                  whos integer value is WARNING to be a warning.

      summary -- A short summary of the event

      detail -- A detailed description

      error -- A three-element tuple consisting of an error type, value, and
               traceback.  If provided, then a summary of the error
               is added to the detail.

      reraise -- If provided with a true value, then the error given by
                 error is reraised.

    """
    log_write(subsystem, severity, summary, detail, error)
    if reraise and error:
        raise error[0], error[1], error[2]

_subsystems=[]
def register_subsystem(subsystem):
    """Register a subsystem name

    A logging facility might replace this function to collect information about
    subsystems used in an application.
    """
    _subsystems.append(subsystem)

# Most apps interested in logging only want the names below.
__all__ = ['LOG', 'TRACE', 'DEBUG', 'BLATHER', 'INFO', 'PROBLEM',
           'WARNING', 'ERROR', 'PANIC', 'log_time']
