celery/celery/log.py

"""celery.log"""
import os
import sys
import time
import logging
from celery.conf import LOG_FORMAT, DAEMON_LOG_LEVEL


def setup_logger(loglevel=DAEMON_LOG_LEVEL, logfile=None, format=LOG_FORMAT,
        **kwargs):
    """Setup the ``multiprocessing`` logger. If ``logfile`` is not specified,
    ``stderr`` is used.

    Returns logger object.
    """
    import multiprocessing
    logger = multiprocessing.get_logger()
    logger.setLevel(loglevel)
    if logger.handlers:
        return logger
    if logfile:
        if hasattr(logfile, "write"):
            log_file_handler = logging.StreamHandler(logfile)
        else:
            log_file_handler = logging.FileHandler(logfile)
        formatter = logging.Formatter(format)
        log_file_handler.setFormatter(formatter)
        logger.addHandler(log_file_handler)
    else:
        multiprocessing.log_to_stderr()
    return logger


def emergency_error(logfile, message):
    """Emergency error logging, for when there's no standard file
    descriptors open because the process has been daemonized or for
    some other reason."""
    logfh_needs_to_close = False
    if not logfile:
        logfile = sys.stderr
    if hasattr(logfile, "write"):
        logfh = logfile
    else:
        logfh = open(logfile, "a")
        logfh_needs_to_close = True
    logfh.write("[%(asctime)s: FATAL/%(pid)d]: %(message)s\n" % {
                    "asctime": time.asctime(),
                    "pid": os.getpid(),
                    "message": message})
    if logfh_needs_to_close:
        logfh.close()


def redirect_stdouts_to_logger(logger, loglevel=None):
    """Redirect :class:`sys.stdout` and :class:`sys.stderr` to a
    logging instance.

    :param logger: The :class:`logging.Logger` instance to redirect to.
    :param loglevel: The loglevel redirected messages will be logged as.

    """
    proxy = LoggingProxy(logger, loglevel)
    sys.stdout = proxy
    sys.stderr = proxy
    return proxy


class LoggingProxy(object):
    """Forward file object to :class:`logging.Logger` instance.

    :param logger: The :class:`logging.Logger` instance to forward to.
    :param loglevel: Loglevel to use when writing messages.

    """
    mode = "w"
    name = None
    closed = False

    def __init__(self, logger, loglevel=logging.INFO):
        self.logger = logger
        self.loglevel = loglevel

    def write(self, data):
        """Write message to logging object."""
        if not self.closed:
            self.logger.log(self.loglevel, data)

    def writelines(self, sequence):
        """``writelines(sequence_of_strings) -> None``.

        Write the strings to the file.

        The sequence can be any iterable object producing strings.
        This is equivalent to calling :meth:`write` for each string.

        """
        map(self.write, sequence)

    def flush(self):
        """This object is not buffered so any :meth:`flush` requests
        are ignored."""
        pass

    def close(self):
        """When the object is closed, no write requests are forwarded to
        the logging object anymore."""
        self.closed = True

    def isatty(self):
        """Always returns ``False``. Just here for file support."""
        return False

    def fileno(self):
        return None