path: root/logging_utils.py

#!/usr/bin/env python3

"""Utilities related to logging."""

import collections
import contextlib
import datetime
import enum
import io
import logging
import os
import random
import sys
from logging.config import fileConfig
from logging.handlers import RotatingFileHandler, SysLogHandler
from typing import Any, Callable, Dict, Iterable, List, Mapping, Optional

import pytz
from overrides import overrides

# This module is commonly used by others in here and should avoid
# taking any unnecessary dependencies back on them.
import argparse_utils
import config

cfg = config.add_commandline_args(f'Logging ({__file__})', 'Args related to logging')
cfg.add_argument(
    '--logging_config_file',
    type=argparse_utils.valid_filename,
    default=None,
    metavar='FILENAME',
    help='Config file containing the logging setup, see: https://docs.python.org/3/howto/logging.html#logging-advanced-tutorial',
)
cfg.add_argument(
    '--logging_level',
    type=str,
    default='INFO',
    choices=['NOTSET', 'DEBUG', 'INFO', 'WARNING', 'ERROR', 'CRITICAL'],
    metavar='LEVEL',
    help='The global default level below which to squelch log messages; see also --lmodule',
)
cfg.add_argument(
    '--logging_format',
    type=str,
    default=None,
    help='The format for lines logged via the logger module.  See: https://docs.python.org/3/library/logging.html#formatter-objects',
)
cfg.add_argument(
    '--logging_date_format',
    type=str,
    default='%Y/%m/%dT%H:%M:%S.%f%z',
    metavar='DATEFMT',
    help='The format of any dates in --logging_format.',
)
cfg.add_argument(
    '--logging_console',
    action=argparse_utils.ActionNoYes,
    default=True,
    help='Should we log to the console (stderr)',
)
cfg.add_argument(
    '--logging_filename',
    type=str,
    default=None,
    metavar='FILENAME',
    help='The filename of the logfile to write.',
)
cfg.add_argument(
    '--logging_filename_maxsize',
    type=int,
    default=(1024 * 1024),
    metavar='#BYTES',
    help='The maximum size (in bytes) to write to the logging_filename.',
)
cfg.add_argument(
    '--logging_filename_count',
    type=int,
    default=7,
    metavar='COUNT',
    help='The number of logging_filename copies to keep before deleting.',
)
cfg.add_argument(
    '--logging_syslog',
    action=argparse_utils.ActionNoYes,
    default=False,
    help='Should we log to localhost\'s syslog.',
)
cfg.add_argument(
    '--logging_syslog_facility',
    type=str,
    default='USER',
    choices=[
        'NOTSET',
        'AUTH',
        'AUTH_PRIV',
        'CRON',
        'DAEMON',
        'FTP',
        'KERN',
        'LPR',
        'MAIL',
        'NEWS',
        'SYSLOG',
        'USER',
        'UUCP',
        'LOCAL0',
        'LOCAL1',
        'LOCAL2',
        'LOCAL3',
        'LOCAL4',
        'LOCAL5',
        'LOCAL6',
        'LOCAL7',
    ],
    metavar='SYSLOG_FACILITY_LIST',
    help='The default syslog message facility identifier',
)
cfg.add_argument(
    '--logging_debug_threads',
    action=argparse_utils.ActionNoYes,
    default=False,
    help='Should we prepend pid/tid data to all log messages?',
)
cfg.add_argument(
    '--logging_debug_modules',
    action=argparse_utils.ActionNoYes,
    default=False,
    help='Should we prepend module/function data to all log messages?',
)
cfg.add_argument(
    '--logging_info_is_print',
    action=argparse_utils.ActionNoYes,
    default=False,
    help='logging.info also prints to stdout.',
)
cfg.add_argument(
    '--logging_squelch_repeats',
    action=argparse_utils.ActionNoYes,
    default=True,
    help='Do we allow code to indicate that it wants to squelch repeated logging messages or should we always log?',
)
cfg.add_argument(
    '--logging_probabilistically',
    action=argparse_utils.ActionNoYes,
    default=True,
    help='Do we allow probabilistic logging (for code that wants it) or should we always log?',
)
# See also: OutputMultiplexer
cfg.add_argument(
    '--logging_captures_prints',
    action=argparse_utils.ActionNoYes,
    default=False,
    help='When calling print, also log.info automatically.',
)
cfg.add_argument(
    '--lmodule',
    type=str,
    metavar='<SCOPE>=<LEVEL>[,<SCOPE>=<LEVEL>...]',
    help=(
        'Allows per-scope logging levels which override the global level set with --logging-level.'
        + 'Pass a space separated list of <scope>=<level> where <scope> is one of: module, '
        + 'module:function, or :function and <level> is a logging level (e.g. INFO, DEBUG...)'
    ),
)
cfg.add_argument(
    '--logging_clear_preexisting_handlers',
    action=argparse_utils.ActionNoYes,
    default=True,
    help=(
        'Should logging code clear preexisting global logging handlers and thus insist that is '
        + 'alone can add handlers.  Use this to work around annoying modules that insert global '
        + 'handlers with formats and logging levels you might now want.  Caveat emptor, this may '
        + 'cause you to miss logging messages.'
    ),
)

built_in_print = print
logging_initialized = False


# A map from logging_callsite_id -> count of logged messages.
squelched_logging_counts: Dict[str, int] = {}


def squelch_repeated_log_messages(squelch_after_n_repeats: int) -> Callable:
    """
    A decorator that marks a function as interested in having the logging
    messages that it produces be squelched (ignored) after it logs the
    same message more than N times.

    Note: this decorator affects *ALL* logging messages produced
    within the decorated function.  That said, messages must be
    identical in order to be squelched.  For example, if the same line
    of code produces different messages (because of, e.g., a format
    string), the messages are considered to be different.

    """

    def squelch_logging_wrapper(f: Callable):
        import function_utils

        identifier = function_utils.function_identifier(f)
        squelched_logging_counts[identifier] = squelch_after_n_repeats
        return f

    return squelch_logging_wrapper


class SquelchRepeatedMessagesFilter(logging.Filter):
    """
    A filter that only logs messages from a given site with the same
    (exact) message at the same logging level N times and ignores
    subsequent attempts to log.

    This filter only affects logging messages that repeat more than
    a threshold number of times from functions that are tagged with
    the @logging_utils.squelched_logging_ok decorator; others are
    ignored.

    This functionality is enabled by default but can be disabled via
    the --no_logging_squelch_repeats commandline flag.

    """

    def __init__(self) -> None:
        super().__init__()
        self.counters: collections.Counter = collections.Counter()

    @overrides
    def filter(self, record: logging.LogRecord) -> bool:
        id1 = f'{record.module}:{record.funcName}'
        if id1 not in squelched_logging_counts:
            return True
        threshold = squelched_logging_counts[id1]
        logsite = f'{record.pathname}+{record.lineno}+{record.levelno}+{record.msg}'
        count = self.counters[logsite]
        self.counters[logsite] += 1
        return count < threshold


class DynamicPerScopeLoggingLevelFilter(logging.Filter):
    """This filter only allows logging messages from an allow list of
    module names or module:function names.  Blocks others.

    """

    @staticmethod
    def level_name_to_level(name: str) -> int:
        numeric_level = getattr(logging, name, None)
        if not isinstance(numeric_level, int):
            raise ValueError(f'Invalid level: {name}')
        return numeric_level

    def __init__(
        self,
        default_logging_level: int,
        per_scope_logging_levels: str,
    ) -> None:
        super().__init__()
        self.valid_levels = set(
            ['NOTSET', 'DEBUG', 'INFO', 'WARNING', 'ERROR', 'CRITICAL']
        )
        self.default_logging_level = default_logging_level
        self.level_by_scope = {}
        if per_scope_logging_levels is not None:
            for chunk in per_scope_logging_levels.split(','):
                if '=' not in chunk:
                    print(
                        f'Malformed lmodule directive: "{chunk}", missing "=".  Ignored.',
                        file=sys.stderr,
                    )
                    continue
                try:
                    (scope, level) = chunk.split('=')
                except ValueError:
                    print(
                        f'Malformed lmodule directive: "{chunk}".  Ignored.',
                        file=sys.stderr,
                    )
                    continue
                scope = scope.strip()
                level = level.strip().upper()
                if level not in self.valid_levels:
                    print(
                        f'Malformed lmodule directive: "{chunk}", bad level.  Ignored.',
                        file=sys.stderr,
                    )
                    continue
                self.level_by_scope[
                    scope
                ] = DynamicPerScopeLoggingLevelFilter.level_name_to_level(level)

    @overrides
    def filter(self, record: logging.LogRecord) -> bool:
        # First try to find a logging level by scope (--lmodule)
        if len(self.level_by_scope) > 0:
            min_level = None
            for scope in (
                record.module,
                f'{record.module}:{record.funcName}',
                f':{record.funcName}',
            ):
                level = self.level_by_scope.get(scope, None)
                if level is not None:
                    if min_level is None or level < min_level:
                        min_level = level

            # If we found one, use it instead of the global default level.
            if min_level is not None:
                return record.levelno >= min_level

        # Otherwise, use the global logging level (--logging_level)
        return record.levelno >= self.default_logging_level


# A map from function_identifier -> probability of logging (0.0%..100.0%)
probabilistic_logging_levels: Dict[str, float] = {}


def logging_is_probabilistic(probability_of_logging: float) -> Callable:
    """
    A decorator that indicates that all logging statements within the
    scope of a particular (marked) function are not deterministic
    (i.e. they do not always unconditionally log) but rather are
    probabilistic (i.e. they log N% of the time randomly).

    Note that this functionality can be disabled (forcing all logged
    messages to produce output) via the --no_logging_probabilistically
    cmdline argument.

    This affects *ALL* logging statements within the marked function.

    """

    def probabilistic_logging_wrapper(f: Callable):
        import function_utils

        identifier = function_utils.function_identifier(f)
        probabilistic_logging_levels[identifier] = probability_of_logging
        return f

    return probabilistic_logging_wrapper


class ProbabilisticFilter(logging.Filter):
    """
    A filter that logs messages probabilistically (i.e. randomly at some
    percent chance).

    This filter only affects logging messages from functions that have
    been tagged with the @logging_utils.probabilistic_logging decorator.

    """

    @overrides
    def filter(self, record: logging.LogRecord) -> bool:
        id1 = f'{record.module}:{record.funcName}'
        if id1 not in probabilistic_logging_levels:
            return True
        threshold = probabilistic_logging_levels[id1]
        return (random.random() * 100.0) <= threshold


class OnlyInfoFilter(logging.Filter):
    """
    A filter that only logs messages produced at the INFO logging
    level.  This is used by the logging_info_is_print commandline
    option to select a subset of the logging stream to send to a
    stdout handler.

    """

    @overrides
    def filter(self, record: logging.LogRecord):
        return record.levelno == logging.INFO


class MillisecondAwareFormatter(logging.Formatter):
    """
    A formatter for adding milliseconds to log messages which, for
    whatever reason, the default python logger doesn't do.

    """

    converter = datetime.datetime.fromtimestamp  # type: ignore

    @overrides
    def formatTime(self, record, datefmt=None):
        ct = MillisecondAwareFormatter.converter(
            record.created, pytz.timezone("US/Pacific")
        )
        if datefmt:
            s = ct.strftime(datefmt)
        else:
            t = ct.strftime("%Y-%m-%d %H:%M:%S")
            s = "%s,%03d" % (t, record.msecs)
        return s


def log_about_logging(
    logger, default_logging_level, preexisting_handlers_count, fmt, facility_name
):
    level_name = logging._levelToName.get(
        default_logging_level, str(default_logging_level)
    )
    logger.debug(f'Initialized global logging; default logging level is {level_name}.')
    if (
        config.config['logging_clear_preexisting_handlers']
        and preexisting_handlers_count > 0
    ):
        msg = f'Logging cleared {preexisting_handlers_count} global handlers (--logging_clear_preexisting_handlers)'
        logger.warning(msg)
    logger.debug(f'Logging format specification is "{fmt}"')
    if config.config['logging_debug_threads']:
        logger.debug(
            '...Logging format spec captures tid/pid (--logging_debug_threads)'
        )
    if config.config['logging_debug_modules']:
        logger.debug(
            '...Logging format spec captures files/functions/lineno (--logging_debug_modules)'
        )
    if config.config['logging_syslog']:
        logger.debug(
            f'Logging to syslog as {facility_name} with priority mapping based on level'
        )
    if config.config['logging_filename']:
        logger.debug(f'Logging to filename {config.config["logging_filename"]}')
        logger.debug(
            f'...with {config.config["logging_filename_maxsize"]} bytes max file size.'
        )
        logger.debug(
            f'...and {config.config["logging_filename_count"]} rotating backup file count.'
        )
    if config.config['logging_console']:
        logger.debug('Logging to the console (stderr).')
    if config.config['logging_info_is_print']:
        logger.debug(
            'Logging logger.info messages will be repeated on stdout (--logging_info_is_print)'
        )
    if config.config['logging_squelch_repeats']:
        logger.debug(
            'Logging code allowed to request repeated messages be squelched (--logging_squelch_repeats)'
        )
    else:
        logger.debug(
            'Logging code forbidden to request messages be squelched; all messages logged (--no_logging_squelch_repeats)'
        )
    if config.config['logging_probabilistically']:
        logger.debug(
            'Logging code is allowed to request probabilistic logging (--logging_probabilistically)'
        )
    else:
        logger.debug(
            'Logging code is forbidden to request probabilistic logging; messages always logged (--no_logging_probabilistically)'
        )
    if config.config['lmodule']:
        logger.debug(
            f'Logging dynamic per-module logging enabled (--lmodule={config.config["lmodule"]})'
        )
    if config.config['logging_captures_prints']:
        logger.debug(
            'Logging will capture printed data as logger.info messages (--logging_captures_prints)'
        )


def initialize_logging(logger=None) -> logging.Logger:
    global logging_initialized
    if logging_initialized:
        return logging.getLogger()
    logging_initialized = True

    if logger is None:
        logger = logging.getLogger()

    preexisting_handlers_count = 0
    assert config.has_been_parsed()
    if config.config['logging_clear_preexisting_handlers']:
        while logger.hasHandlers():
            logger.removeHandler(logger.handlers[0])
            preexisting_handlers_count += 1

    if config.config['logging_config_file'] is not None:
        fileConfig(config.config['logging_config_file'])
        return logger

    handlers: List[logging.Handler] = []
    handler: Optional[logging.Handler] = None

    # Global default logging level (--logging_level)
    default_logging_level = getattr(
        logging, config.config['logging_level'].upper(), None
    )
    if not isinstance(default_logging_level, int):
        raise ValueError('Invalid level: %s' % config.config['logging_level'])

    if config.config['logging_format']:
        fmt = config.config['logging_format']
    else:
        if config.config['logging_syslog']:
            fmt = '%(levelname).1s:%(filename)s[%(process)d]: %(message)s'
        else:
            fmt = '%(levelname).1s:%(asctime)s: %(message)s'
    if config.config['logging_debug_threads']:
        fmt = f'%(process)d.%(thread)d|{fmt}'
    if config.config['logging_debug_modules']:
        fmt = f'%(filename)s:%(funcName)s:%(lineno)s|{fmt}'

    facility_name = None
    if config.config['logging_syslog']:
        if sys.platform not in ('win32', 'cygwin'):
            if config.config['logging_syslog_facility']:
                facility_name = 'LOG_' + config.config['logging_syslog_facility']
            facility = SysLogHandler.__dict__.get(facility_name, SysLogHandler.LOG_USER)  # type: ignore
            assert facility is not None
            handler = SysLogHandler(facility=facility, address='/dev/log')
            handler.setFormatter(
                MillisecondAwareFormatter(
                    fmt=fmt,
                    datefmt=config.config['logging_date_format'],
                )
            )
            handlers.append(handler)

    if config.config['logging_filename']:
        handler = RotatingFileHandler(
            config.config['logging_filename'],
            maxBytes=config.config['logging_filename_maxsize'],
            backupCount=config.config['logging_filename_count'],
        )
        handler.setFormatter(
            MillisecondAwareFormatter(
                fmt=fmt,
                datefmt=config.config['logging_date_format'],
            )
        )
        handlers.append(handler)

    if config.config['logging_console']:
        handler = logging.StreamHandler(sys.stderr)
        handler.setFormatter(
            MillisecondAwareFormatter(
                fmt=fmt,
                datefmt=config.config['logging_date_format'],
            )
        )
        handlers.append(handler)

    if len(handlers) == 0:
        handlers.append(logging.NullHandler())

    for handler in handlers:
        logger.addHandler(handler)

    if config.config['logging_info_is_print']:
        handler = logging.StreamHandler(sys.stdout)
        handler.addFilter(OnlyInfoFilter())
        logger.addHandler(handler)

    if config.config['logging_squelch_repeats']:
        for handler in handlers:
            handler.addFilter(SquelchRepeatedMessagesFilter())

    if config.config['logging_probabilistically']:
        for handler in handlers:
            handler.addFilter(ProbabilisticFilter())

    for handler in handlers:
        handler.addFilter(
            DynamicPerScopeLoggingLevelFilter(
                default_logging_level,
                config.config['lmodule'],
            )
        )
    logger.setLevel(0)
    logger.propagate = False

    if config.config['logging_captures_prints']:
        global built_in_print
        import builtins

        def print_and_also_log(*arg, **kwarg):
            f = kwarg.get('file', None)
            if f == sys.stderr:
                logger.warning(*arg)
            else:
                logger.info(*arg)
            built_in_print(*arg, **kwarg)

        builtins.print = print_and_also_log

    # At this point the logger is ready, handlers are set up,
    # etc... so log about the logging configuration.
    log_about_logging(
        logger,
        default_logging_level,
        preexisting_handlers_count,
        fmt,
        facility_name,
    )
    return logger


def get_logger(name: str = ""):
    logger = logging.getLogger(name)
    return initialize_logging(logger)


def tprint(*args, **kwargs) -> None:
    """Legacy function for printing a message augmented with thread id
    still needed by some code.  Please use --logging_debug_threads in
    new code.

    """
    if config.config['logging_debug_threads']:
        from thread_utils import current_thread_id

        print(f'{current_thread_id()}', end="")
        print(*args, **kwargs)
    else:
        pass


def dprint(*args, **kwargs) -> None:
    """Legacy function used to print to stderr still needed by some code.
    Please just use normal logging with --logging_console which
    accomplishes the same thing in new code.

    """
    print(*args, file=sys.stderr, **kwargs)


class OutputMultiplexer(object):
    """
    A class that broadcasts printed messages to several sinks (including
    various logging levels, different files, different file handles,
    the house log, etc...).  See also OutputMultiplexerContext for an
    easy usage pattern.

    """

    class Destination(enum.IntEnum):
        """Bits in the destination_bitv bitvector.  Used to indicate the
        output destination."""

        # fmt: off
        LOG_DEBUG = 0x01     #  ⎫
        LOG_INFO = 0x02      #  ⎪
        LOG_WARNING = 0x04   #  ⎬ Must provide logger to the c'tor.
        LOG_ERROR = 0x08     #  ⎪
        LOG_CRITICAL = 0x10  #  ⎭
        FILENAMES = 0x20     # Must provide a filename to the c'tor.
        FILEHANDLES = 0x40   # Must provide a handle to the c'tor.
        HLOG = 0x80
        ALL_LOG_DESTINATIONS = (
            LOG_DEBUG | LOG_INFO | LOG_WARNING | LOG_ERROR | LOG_CRITICAL
        )
        ALL_OUTPUT_DESTINATIONS = 0x8F
        # fmt: on

    def __init__(
        self,
        destination_bitv: int,
        *,
        logger=None,
        filenames: Optional[Iterable[str]] = None,
        handles: Optional[Iterable[io.TextIOWrapper]] = None,
    ):
        if logger is None:
            logger = logging.getLogger(None)
        self.logger = logger

        self.f: Optional[List[Any]] = None
        if filenames is not None:
            self.f = [open(filename, 'wb', buffering=0) for filename in filenames]
        else:
            if destination_bitv & OutputMultiplexer.Destination.FILENAMES:
                raise ValueError("Filenames argument is required if bitv & FILENAMES")
            self.f = None

        self.h: Optional[List[Any]] = None
        if handles is not None:
            self.h = [handle for handle in handles]
        else:
            if destination_bitv & OutputMultiplexer.Destination.FILEHANDLES:
                raise ValueError("Handle argument is required if bitv & FILEHANDLES")
            self.h = None

        self.set_destination_bitv(destination_bitv)

    def get_destination_bitv(self):
        return self.destination_bitv

    def set_destination_bitv(self, destination_bitv: int):
        if destination_bitv & self.Destination.FILENAMES and self.f is None:
            raise ValueError("Filename argument is required if bitv & FILENAMES")
        if destination_bitv & self.Destination.FILEHANDLES and self.h is None:
            raise ValueError("Handle argument is required if bitv & FILEHANDLES")
        self.destination_bitv = destination_bitv

    def print(self, *args, **kwargs):
        from string_utils import sprintf, strip_escape_sequences

        end = kwargs.pop("end", None)
        if end is not None:
            if not isinstance(end, str):
                raise TypeError("end must be None or a string")
        sep = kwargs.pop("sep", None)
        if sep is not None:
            if not isinstance(sep, str):
                raise TypeError("sep must be None or a string")
        if kwargs:
            raise TypeError("invalid keyword arguments to print()")
        buf = sprintf(*args, end="", sep=sep)
        if sep is None:
            sep = " "
        if end is None:
            end = "\n"
        if end == '\n':
            buf += '\n'
        if self.destination_bitv & self.Destination.FILENAMES and self.f is not None:
            for _ in self.f:
                _.write(buf.encode('utf-8'))
                _.flush()

        if self.destination_bitv & self.Destination.FILEHANDLES and self.h is not None:
            for _ in self.h:
                _.write(buf)
                _.flush()

        buf = strip_escape_sequences(buf)
        if self.logger is not None:
            if self.destination_bitv & self.Destination.LOG_DEBUG:
                self.logger.debug(buf)
            if self.destination_bitv & self.Destination.LOG_INFO:
                self.logger.info(buf)
            if self.destination_bitv & self.Destination.LOG_WARNING:
                self.logger.warning(buf)
            if self.destination_bitv & self.Destination.LOG_ERROR:
                self.logger.error(buf)
            if self.destination_bitv & self.Destination.LOG_CRITICAL:
                self.logger.critical(buf)
        if self.destination_bitv & self.Destination.HLOG:
            hlog(buf)

    def close(self):
        if self.f is not None:
            for _ in self.f:
                _.close()


class OutputMultiplexerContext(OutputMultiplexer, contextlib.ContextDecorator):
    """
    A context that uses an OutputMultiplexer.  e.g.

        with OutputMultiplexerContext(
                OutputMultiplexer.LOG_INFO |
                OutputMultiplexer.LOG_DEBUG |
                OutputMultiplexer.FILENAMES |
                OutputMultiplexer.FILEHANDLES,
                filenames = [ '/tmp/foo.log', '/var/log/bar.log' ],
                handles = [ f, g ]
            ) as mplex:
                mplex.print("This is a log message!")

    """

    def __init__(
        self,
        destination_bitv: OutputMultiplexer.Destination,
        *,
        logger=None,
        filenames=None,
        handles=None,
    ):
        super().__init__(
            destination_bitv,
            logger=logger,
            filenames=filenames,
            handles=handles,
        )

    def __enter__(self):
        return self

    def __exit__(self, etype, value, traceback) -> bool:
        super().close()
        if etype is not None:
            return False
        return True


def hlog(message: str) -> None:
    """Write a message to the house log (syslog facility local7 priority
    info) by calling /usr/bin/logger.  This is pretty hacky but used
    by a bunch of code.  Another way to do this would be to use
    --logging_syslog and --logging_syslog_facility but I can't
    actually say that's easier.

    """
    message = message.replace("'", "'\"'\"'")
    os.system(f"/usr/bin/logger -p local7.info -- '{message}'")


if __name__ == '__main__':
    import doctest

    doctest.testmod()