Lib/test/test_logging.py

#!/usr/bin/env python
#
# Copyright 2001-2010 by Vinay Sajip. All Rights Reserved.
#
# Permission to use, copy, modify, and distribute this software and its
# documentation for any purpose and without fee is hereby granted,
# provided that the above copyright notice appear in all copies and that
# both that copyright notice and this permission notice appear in
# supporting documentation, and that the name of Vinay Sajip
# not be used in advertising or publicity pertaining to distribution
# of the software without specific, written prior permission.
# VINAY SAJIP DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING
# ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL
# VINAY SAJIP BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR
# ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER
# IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
# OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

"""Test harness for the logging module. Run all tests.

Copyright (C) 2001-2010 Vinay Sajip. All Rights Reserved.
"""

import logging
import logging.handlers
import logging.config

import codecs
import copy
import cPickle
import cStringIO
import gc
import os
import re
import select
import socket
from SocketServer import ThreadingTCPServer, StreamRequestHandler
import string
import struct
import sys
import tempfile
from test.test_support import captured_stdout, run_with_locale, run_unittest
import textwrap
import threading
import time
import types
import unittest
import weakref


class BaseTest(unittest.TestCase):

    """Base class for logging tests."""

    log_format = "%(name)s -> %(levelname)s: %(message)s"
    expected_log_pat = r"^([\w.]+) -> ([\w]+): ([\d]+)$"
    message_num = 0

    def setUp(self):
        """Setup the default logging stream to an internal StringIO instance,
        so that we can examine log output as we want."""
        logger_dict = logging.getLogger().manager.loggerDict
        logging._acquireLock()
        try:
            self.saved_handlers = logging._handlers.copy()
            self.saved_handler_list = logging._handlerList[:]
            self.saved_loggers = logger_dict.copy()
            self.saved_level_names = logging._levelNames.copy()
        finally:
            logging._releaseLock()

        # Set two unused loggers: one non-ASCII and one Unicode.
        # This is to test correct operation when sorting existing
        # loggers in the configuration code. See issues 8201, 9310.
        logging.getLogger("\xab\xd7\xbb")
        logging.getLogger(u"\u013f\u00d6\u0047")

        self.root_logger = logging.getLogger("")
        self.original_logging_level = self.root_logger.getEffectiveLevel()

        self.stream = cStringIO.StringIO()
        self.root_logger.setLevel(logging.DEBUG)
        self.root_hdlr = logging.StreamHandler(self.stream)
        self.root_formatter = logging.Formatter(self.log_format)
        self.root_hdlr.setFormatter(self.root_formatter)
        self.root_logger.addHandler(self.root_hdlr)

    def tearDown(self):
        """Remove our logging stream, and restore the original logging
        level."""
        self.stream.close()
        self.root_logger.removeHandler(self.root_hdlr)
        self.root_logger.setLevel(self.original_logging_level)
        logging._acquireLock()
        try:
            logging._levelNames.clear()
            logging._levelNames.update(self.saved_level_names)
            logging._handlers.clear()
            logging._handlers.update(self.saved_handlers)
            logging._handlerList[:] = self.saved_handler_list
            loggerDict = logging.getLogger().manager.loggerDict
            loggerDict.clear()
            loggerDict.update(self.saved_loggers)
        finally:
            logging._releaseLock()

    def assert_log_lines(self, expected_values, stream=None):
        """Match the collected log lines against the regular expression
        self.expected_log_pat, and compare the extracted group values to
        the expected_values list of tuples."""
        stream = stream or self.stream
        pat = re.compile(self.expected_log_pat)
        try:
            stream.reset()
            actual_lines = stream.readlines()
        except AttributeError:
            # StringIO.StringIO lacks a reset() method.
            actual_lines = stream.getvalue().splitlines()
        self.assertEquals(len(actual_lines), len(expected_values))
        for actual, expected in zip(actual_lines, expected_values):
            match = pat.search(actual)
            if not match:
                self.fail("Log line does not match expected pattern:\n" +
                            actual)
            self.assertEquals(tuple(match.groups()), expected)
        s = stream.read()
        if s:
            self.fail("Remaining output at end of log stream:\n" + s)

    def next_message(self):
        """Generate a message consisting solely of an auto-incrementing
        integer."""
        self.message_num += 1
        return "%d" % self.message_num


class BuiltinLevelsTest(BaseTest):
    """Test builtin levels and their inheritance."""

    def test_flat(self):
        #Logging levels in a flat logger namespace.
        m = self.next_message

        ERR = logging.getLogger("ERR")
        ERR.setLevel(logging.ERROR)
        INF = logging.getLogger("INF")
        INF.setLevel(logging.INFO)
        DEB = logging.getLogger("DEB")
        DEB.setLevel(logging.DEBUG)

        # These should log.
        ERR.log(logging.CRITICAL, m())
        ERR.error(m())

        INF.log(logging.CRITICAL, m())
        INF.error(m())
        INF.warn(m())
        INF.info(m())

        DEB.log(logging.CRITICAL, m())
        DEB.error(m())
        DEB.warn (m())
        DEB.info (m())
        DEB.debug(m())

        # These should not log.
        ERR.warn(m())
        ERR.info(m())
        ERR.debug(m())

        INF.debug(m())

        self.assert_log_lines([
            ('ERR', 'CRITICAL', '1'),
            ('ERR', 'ERROR', '2'),
            ('INF', 'CRITICAL', '3'),
            ('INF', 'ERROR', '4'),
            ('INF', 'WARNING', '5'),
            ('INF', 'INFO', '6'),
            ('DEB', 'CRITICAL', '7'),
            ('DEB', 'ERROR', '8'),
            ('DEB', 'WARNING', '9'),
            ('DEB', 'INFO', '10'),
            ('DEB', 'DEBUG', '11'),
        ])

    def test_nested_explicit(self):
        # Logging levels in a nested namespace, all explicitly set.
        m = self.next_message

        INF = logging.getLogger("INF")
        INF.setLevel(logging.INFO)
        INF_ERR  = logging.getLogger("INF.ERR")
        INF_ERR.setLevel(logging.ERROR)

        # These should log.
        INF_ERR.log(logging.CRITICAL, m())
        INF_ERR.error(m())

        # These should not log.
        INF_ERR.warn(m())
        INF_ERR.info(m())
        INF_ERR.debug(m())

        self.assert_log_lines([
            ('INF.ERR', 'CRITICAL', '1'),
            ('INF.ERR', 'ERROR', '2'),
        ])

    def test_nested_inherited(self):
        #Logging levels in a nested namespace, inherited from parent loggers.
        m = self.next_message

        INF = logging.getLogger("INF")
        INF.setLevel(logging.INFO)
        INF_ERR  = logging.getLogger("INF.ERR")
        INF_ERR.setLevel(logging.ERROR)
        INF_UNDEF = logging.getLogger("INF.UNDEF")
        INF_ERR_UNDEF = logging.getLogger("INF.ERR.UNDEF")
        UNDEF = logging.getLogger("UNDEF")

        # These should log.
        INF_UNDEF.log(logging.CRITICAL, m())
        INF_UNDEF.error(m())
        INF_UNDEF.warn(m())
        INF_UNDEF.info(m())
        INF_ERR_UNDEF.log(logging.CRITICAL, m())
        INF_ERR_UNDEF.error(m())

        # These should not log.
        INF_UNDEF.debug(m())
        INF_ERR_UNDEF.warn(m())
        INF_ERR_UNDEF.info(m())
        INF_ERR_UNDEF.debug(m())

        self.assert_log_lines([
            ('INF.UNDEF', 'CRITICAL', '1'),
            ('INF.UNDEF', 'ERROR', '2'),
            ('INF.UNDEF', 'WARNING', '3'),
            ('INF.UNDEF', 'INFO', '4'),
            ('INF.ERR.UNDEF', 'CRITICAL', '5'),
            ('INF.ERR.UNDEF', 'ERROR', '6'),
        ])

    def test_nested_with_virtual_parent(self):
        # Logging levels when some parent does not exist yet.
        m = self.next_message

        INF = logging.getLogger("INF")
        GRANDCHILD = logging.getLogger("INF.BADPARENT.UNDEF")
        CHILD = logging.getLogger("INF.BADPARENT")
        INF.setLevel(logging.INFO)

        # These should log.
        GRANDCHILD.log(logging.FATAL, m())
        GRANDCHILD.info(m())
        CHILD.log(logging.FATAL, m())
        CHILD.info(m())

        # These should not log.
        GRANDCHILD.debug(m())
        CHILD.debug(m())

        self.assert_log_lines([
            ('INF.BADPARENT.UNDEF', 'CRITICAL', '1'),
            ('INF.BADPARENT.UNDEF', 'INFO', '2'),
            ('INF.BADPARENT', 'CRITICAL', '3'),
            ('INF.BADPARENT', 'INFO', '4'),
        ])


class BasicFilterTest(BaseTest):

    """Test the bundled Filter class."""

    def test_filter(self):
        # Only messages satisfying the specified criteria pass through the
        #  filter.
        filter_ = logging.Filter("spam.eggs")
        handler = self.root_logger.handlers[0]
        try:
            handler.addFilter(filter_)
            spam = logging.getLogger("spam")
            spam_eggs = logging.getLogger("spam.eggs")
            spam_eggs_fish = logging.getLogger("spam.eggs.fish")
            spam_bakedbeans = logging.getLogger("spam.bakedbeans")

            spam.info(self.next_message())
            spam_eggs.info(self.next_message())  # Good.
            spam_eggs_fish.info(self.next_message())  # Good.
            spam_bakedbeans.info(self.next_message())

            self.assert_log_lines([
                ('spam.eggs', 'INFO', '2'),
                ('spam.eggs.fish', 'INFO', '3'),
            ])
        finally:
            handler.removeFilter(filter_)


#
#   First, we define our levels. There can be as many as you want - the only
#     limitations are that they should be integers, the lowest should be > 0 and
#   larger values mean less information being logged. If you need specific
#   level values which do not fit into these limitations, you can use a
#   mapping dictionary to convert between your application levels and the
#   logging system.
#
SILENT      = 120
TACITURN    = 119
TERSE       = 118
EFFUSIVE    = 117
SOCIABLE    = 116
VERBOSE     = 115
TALKATIVE   = 114
GARRULOUS   = 113
CHATTERBOX  = 112
BORING      = 111

LEVEL_RANGE = range(BORING, SILENT + 1)

#
#   Next, we define names for our levels. You don't need to do this - in which
#   case the system will use "Level n" to denote the text for the level.
#
my_logging_levels = {
    SILENT      : 'Silent',
    TACITURN    : 'Taciturn',
    TERSE       : 'Terse',
    EFFUSIVE    : 'Effusive',
    SOCIABLE    : 'Sociable',
    VERBOSE     : 'Verbose',
    TALKATIVE   : 'Talkative',
    GARRULOUS   : 'Garrulous',
    CHATTERBOX  : 'Chatterbox',
    BORING      : 'Boring',
}

class GarrulousFilter(logging.Filter):

    """A filter which blocks garrulous messages."""

    def filter(self, record):
        return record.levelno != GARRULOUS

class VerySpecificFilter(logging.Filter):

    """A filter which blocks sociable and taciturn messages."""

    def filter(self, record):
        return record.levelno not in [SOCIABLE, TACITURN]


class CustomLevelsAndFiltersTest(BaseTest):

    """Test various filtering possibilities with custom logging levels."""

    # Skip the logger name group.
    expected_log_pat = r"^[\w.]+ -> ([\w]+): ([\d]+)$"

    def setUp(self):
        BaseTest.setUp(self)
        for k, v in my_logging_levels.items():
            logging.addLevelName(k, v)

    def log_at_all_levels(self, logger):
        for lvl in LEVEL_RANGE:
            logger.log(lvl, self.next_message())

    def test_logger_filter(self):
        # Filter at logger level.
        self.root_logger.setLevel(VERBOSE)
        # Levels >= 'Verbose' are good.
        self.log_at_all_levels(self.root_logger)
        self.assert_log_lines([
            ('Verbose', '5'),
            ('Sociable', '6'),
            ('Effusive', '7'),
            ('Terse', '8'),
            ('Taciturn', '9'),
            ('Silent', '10'),
        ])

    def test_handler_filter(self):
        # Filter at handler level.
        self.root_logger.handlers[0].setLevel(SOCIABLE)
        try:
            # Levels >= 'Sociable' are good.
            self.log_at_all_levels(self.root_logger)
            self.assert_log_lines([
                ('Sociable', '6'),
                ('Effusive', '7'),
                ('Terse', '8'),
                ('Taciturn', '9'),
                ('Silent', '10'),
            ])
        finally:
            self.root_logger.handlers[0].setLevel(logging.NOTSET)

    def test_specific_filters(self):
        # Set a specific filter object on the handler, and then add another
        #  filter object on the logger itself.
        handler = self.root_logger.handlers[0]
        specific_filter = None
        garr = GarrulousFilter()
        handler.addFilter(garr)
        try:
            self.log_at_all_levels(self.root_logger)
            first_lines = [
                # Notice how 'Garrulous' is missing
                ('Boring', '1'),
                ('Chatterbox', '2'),
                ('Talkative', '4'),
                ('Verbose', '5'),
                ('Sociable', '6'),
                ('Effusive', '7'),
                ('Terse', '8'),
                ('Taciturn', '9'),
                ('Silent', '10'),
            ]
            self.assert_log_lines(first_lines)

            specific_filter = VerySpecificFilter()
            self.root_logger.addFilter(specific_filter)
            self.log_at_all_levels(self.root_logger)
            self.assert_log_lines(first_lines + [
                # Not only 'Garrulous' is still missing, but also 'Sociable'
                # and 'Taciturn'
                ('Boring', '11'),
                ('Chatterbox', '12'),
                ('Talkative', '14'),
                ('Verbose', '15'),
                ('Effusive', '17'),
                ('Terse', '18'),
                ('Silent', '20'),
        ])
        finally:
            if specific_filter:
                self.root_logger.removeFilter(specific_filter)
            handler.removeFilter(garr)


class MemoryHandlerTest(BaseTest):

    """Tests for the MemoryHandler."""

    # Do not bother with a logger name group.
    expected_log_pat = r"^[\w.]+ -> ([\w]+): ([\d]+)$"

    def setUp(self):
        BaseTest.setUp(self)
        self.mem_hdlr = logging.handlers.MemoryHandler(10, logging.WARNING,
                                                        self.root_hdlr)
        self.mem_logger = logging.getLogger('mem')
        self.mem_logger.propagate = 0
        self.mem_logger.addHandler(self.mem_hdlr)

    def tearDown(self):
        self.mem_hdlr.close()
        BaseTest.tearDown(self)

    def test_flush(self):
        # The memory handler flushes to its target handler based on specific
        #  criteria (message count and message level).
        self.mem_logger.debug(self.next_message())
        self.assert_log_lines([])
        self.mem_logger.info(self.next_message())
        self.assert_log_lines([])
        # This will flush because the level is >= logging.WARNING
        self.mem_logger.warn(self.next_message())
        lines = [
            ('DEBUG', '1'),
            ('INFO', '2'),
            ('WARNING', '3'),
        ]
        self.assert_log_lines(lines)
        for n in (4, 14):
            for i in range(9):
                self.mem_logger.debug(self.next_message())
            self.assert_log_lines(lines)
            # This will flush because it's the 10th message since the last
            #  flush.
            self.mem_logger.debug(self.next_message())
            lines = lines + [('DEBUG', str(i)) for i in range(n, n + 10)]
            self.assert_log_lines(lines)

        self.mem_logger.debug(self.next_message())
        self.assert_log_lines(lines)


class ExceptionFormatter(logging.Formatter):
    """A special exception formatter."""
    def formatException(self, ei):
        return "Got a [%s]" % ei[0].__name__


class ConfigFileTest(BaseTest):

    """Reading logging config from a .ini-style config file."""

    expected_log_pat = r"^([\w]+) \+\+ ([\w]+)$"

    # config0 is a standard configuration.
    config0 = """
    [loggers]
    keys=root

    [handlers]
    keys=hand1

    [formatters]
    keys=form1

    [logger_root]
    level=WARNING
    handlers=hand1

    [handler_hand1]
    class=StreamHandler
    level=NOTSET
    formatter=form1
    args=(sys.stdout,)

    [formatter_form1]
    format=%(levelname)s ++ %(message)s
    datefmt=
    """

    # config1 adds a little to the standard configuration.
    config1 = """
    [loggers]
    keys=root,parser

    [handlers]
    keys=hand1

    [formatters]
    keys=form1

    [logger_root]
    level=WARNING
    handlers=

    [logger_parser]
    level=DEBUG
    handlers=hand1
    propagate=1
    qualname=compiler.parser

    [handler_hand1]
    class=StreamHandler
    level=NOTSET
    formatter=form1
    args=(sys.stdout,)

    [formatter_form1]
    format=%(levelname)s ++ %(message)s
    datefmt=
    """

    # config2 has a subtle configuration error that should be reported
    config2 = config1.replace("sys.stdout", "sys.stbout")

    # config3 has a less subtle configuration error
    config3 = config1.replace("formatter=form1", "formatter=misspelled_name")

    # config4 specifies a custom formatter class to be loaded
    config4 = """
    [loggers]
    keys=root

    [handlers]
    keys=hand1

    [formatters]
    keys=form1

    [logger_root]
    level=NOTSET
    handlers=hand1

    [handler_hand1]
    class=StreamHandler
    level=NOTSET
    formatter=form1
    args=(sys.stdout,)

    [formatter_form1]
    class=""" + __name__ + """.ExceptionFormatter
    format=%(levelname)s:%(name)s:%(message)s
    datefmt=
    """

    # config5 specifies a custom handler class to be loaded
    config5 = config1.replace('class=StreamHandler', 'class=logging.StreamHandler')

    # config6 uses ', ' delimiters in the handlers and formatters sections
    config6 = """
    [loggers]
    keys=root,parser

    [handlers]
    keys=hand1, hand2

    [formatters]
    keys=form1, form2

    [logger_root]
    level=WARNING
    handlers=

    [logger_parser]
    level=DEBUG
    handlers=hand1
    propagate=1
    qualname=compiler.parser

    [handler_hand1]
    class=StreamHandler
    level=NOTSET
    formatter=form1
    args=(sys.stdout,)

    [handler_hand2]
    class=StreamHandler
    level=NOTSET
    formatter=form1
    args=(sys.stderr,)

    [formatter_form1]
    format=%(levelname)s ++ %(message)s
    datefmt=

    [formatter_form2]
    format=%(message)s
    datefmt=
    """

    def apply_config(self, conf):
        try:
            fn = tempfile.mktemp(".ini")
            f = open(fn, "w")
            f.write(textwrap.dedent(conf))
            f.close()
            logging.config.fileConfig(fn)
        finally:
            os.remove(fn)

    def test_config0_ok(self):
        # A simple config file which overrides the default settings.
        with captured_stdout() as output:
            self.apply_config(self.config0)
            logger = logging.getLogger()
            # Won't output anything
            logger.info(self.next_message())
            # Outputs a message
            logger.error(self.next_message())
            self.assert_log_lines([
                ('ERROR', '2'),
            ], stream=output)
            # Original logger output is empty.
            self.assert_log_lines([])

    def test_config1_ok(self, config=config1):
        # A config file defining a sub-parser as well.
        with captured_stdout() as output:
            self.apply_config(config)
            logger = logging.getLogger("compiler.parser")
            # Both will output a message
            logger.info(self.next_message())
            logger.error(self.next_message())
            self.assert_log_lines([
                ('INFO', '1'),
                ('ERROR', '2'),
            ], stream=output)
            # Original logger output is empty.
            self.assert_log_lines([])

    def test_config2_failure(self):
        # A simple config file which overrides the default settings.
        self.assertRaises(StandardError, self.apply_config, self.config2)

    def test_config3_failure(self):
        # A simple config file which overrides the default settings.
        self.assertRaises(StandardError, self.apply_config, self.config3)

    def test_config4_ok(self):
        # A config file specifying a custom formatter class.
        with captured_stdout() as output:
            self.apply_config(self.config4)
            logger = logging.getLogger()
            try:
                raise RuntimeError()
            except RuntimeError:
                logging.exception("just testing")
            sys.stdout.seek(0)
            self.assertEquals(output.getvalue(),
                "ERROR:root:just testing\nGot a [RuntimeError]\n")
            # Original logger output is empty
            self.assert_log_lines([])

    def test_config5_ok(self):
        self.test_config1_ok(config=self.config5)

    def test_config6_ok(self):
        self.test_config1_ok(config=self.config6)

class LogRecordStreamHandler(StreamRequestHandler):

    """Handler for a streaming logging request. It saves the log message in the
    TCP server's 'log_output' attribute."""

    TCP_LOG_END = "!!!END!!!"

    def handle(self):
        """Handle multiple requests - each expected to be of 4-byte length,
        followed by the LogRecord in pickle format. Logs the record
        according to whatever policy is configured locally."""
        while True:
            chunk = self.connection.recv(4)
            if len(chunk) < 4:
                break
            slen = struct.unpack(">L", chunk)[0]
            chunk = self.connection.recv(slen)
            while len(chunk) < slen:
                chunk = chunk + self.connection.recv(slen - len(chunk))
            obj = self.unpickle(chunk)
            record = logging.makeLogRecord(obj)
            self.handle_log_record(record)

    def unpickle(self, data):
        return cPickle.loads(data)

    def handle_log_record(self, record):
        # If the end-of-messages sentinel is seen, tell the server to
        #  terminate.
        if self.TCP_LOG_END in record.msg:
            self.server.abort = 1
            return
        self.server.log_output += record.msg + "\n"


class LogRecordSocketReceiver(ThreadingTCPServer):

    """A simple-minded TCP socket-based logging receiver suitable for test
    purposes."""

    allow_reuse_address = 1
    log_output = ""

    def __init__(self, host='localhost',
                             port=logging.handlers.DEFAULT_TCP_LOGGING_PORT,
                     handler=LogRecordStreamHandler):
        ThreadingTCPServer.__init__(self, (host, port), handler)
        self.abort = False
        self.timeout = 0.1
        self.finished = threading.Event()

    def serve_until_stopped(self):
        while not self.abort:
            rd, wr, ex = select.select([self.socket.fileno()], [], [],
                                       self.timeout)
            if rd:
                self.handle_request()
        # Notify the main thread that we're about to exit
        self.finished.set()
        # close the listen socket
        self.server_close()


class SocketHandlerTest(BaseTest):

    """Test for SocketHandler objects."""

    def setUp(self):
        """Set up a TCP server to receive log messages, and a SocketHandler
        pointing to that server's address and port."""
        BaseTest.setUp(self)
        self.tcpserver = LogRecordSocketReceiver(port=0)
        self.port = self.tcpserver.socket.getsockname()[1]
        self.threads = [
                threading.Thread(target=self.tcpserver.serve_until_stopped)]
        for thread in self.threads:
            thread.start()

        self.sock_hdlr = logging.handlers.SocketHandler('localhost', self.port)
        self.sock_hdlr.setFormatter(self.root_formatter)
        self.root_logger.removeHandler(self.root_logger.handlers[0])
        self.root_logger.addHandler(self.sock_hdlr)

    def tearDown(self):
        """Shutdown the TCP server."""
        try:
            self.tcpserver.abort = True
            del self.tcpserver
            self.root_logger.removeHandler(self.sock_hdlr)
            self.sock_hdlr.close()
            for thread in self.threads:
                thread.join(2.0)
        finally:
            BaseTest.tearDown(self)

    def get_output(self):
        """Get the log output as received by the TCP server."""
        # Signal the TCP receiver and wait for it to terminate.
        self.root_logger.critical(LogRecordStreamHandler.TCP_LOG_END)
        self.tcpserver.finished.wait(2.0)
        return self.tcpserver.log_output

    def test_output(self):
        # The log message sent to the SocketHandler is properly received.
        logger = logging.getLogger("tcp")
        logger.error("spam")
        logger.debug("eggs")
        self.assertEquals(self.get_output(), "spam\neggs\n")


class MemoryTest(BaseTest):

    """Test memory persistence of logger objects."""

    def setUp(self):
        """Create a dict to remember potentially destroyed objects."""
        BaseTest.setUp(self)
        self._survivors = {}

    def _watch_for_survival(self, *args):
        """Watch the given objects for survival, by creating weakrefs to
        them."""
        for obj in args:
            key = id(obj), repr(obj)
            self._survivors[key] = weakref.ref(obj)

    def _assert_survival(self):
        """Assert that all objects watched for survival have survived."""
        # Trigger cycle breaking.
        gc.collect()
        dead = []
        for (id_, repr_), ref in self._survivors.items():
            if ref() is None:
                dead.append(repr_)
        if dead:
            self.fail("%d objects should have survived "
                "but have been destroyed: %s" % (len(dead), ", ".join(dead)))

    def test_persistent_loggers(self):
        # Logger objects are persistent and retain their configuration, even
        #  if visible references are destroyed.
        self.root_logger.setLevel(logging.INFO)
        foo = logging.getLogger("foo")
        self._watch_for_survival(foo)
        foo.setLevel(logging.DEBUG)
        self.root_logger.debug(self.next_message())
        foo.debug(self.next_message())
        self.assert_log_lines([
            ('foo', 'DEBUG', '2'),
        ])
        del foo
        # foo has survived.
        self._assert_survival()
        # foo has retained its settings.
        bar = logging.getLogger("foo")
        bar.debug(self.next_message())
        self.assert_log_lines([
            ('foo', 'DEBUG', '2'),
            ('foo', 'DEBUG', '3'),
        ])


class EncodingTest(BaseTest):
    def test_encoding_plain_file(self):
        # In Python 2.x, a plain file object is treated as having no encoding.
        log = logging.getLogger("test")
        fn = tempfile.mktemp(".log")
        # the non-ascii data we write to the log.
        data = "foo\x80"
        try:
            handler = logging.FileHandler(fn)
            log.addHandler(handler)
            try:
                # write non-ascii data to the log.
                log.warning(data)
            finally:
                log.removeHandler(handler)
                handler.close()
            # check we wrote exactly those bytes, ignoring trailing \n etc
            f = open(fn)
            try:
                self.failUnlessEqual(f.read().rstrip(), data)
            finally:
                f.close()
        finally:
            if os.path.isfile(fn):
                os.remove(fn)

    def test_encoding_cyrillic_unicode(self):
        log = logging.getLogger("test")
        #Get a message in Unicode: Do svidanya in Cyrillic (meaning goodbye)
        message = u'\u0434\u043e \u0441\u0432\u0438\u0434\u0430\u043d\u0438\u044f'
        #Ensure it's written in a Cyrillic encoding
        writer_class = codecs.getwriter('cp1251')
        writer_class.encoding = 'cp1251'
        stream = cStringIO.StringIO()
        writer = writer_class(stream, 'strict')
        handler = logging.StreamHandler(writer)
        log.addHandler(handler)
        try:
            log.warning(message)
        finally:
            log.removeHandler(handler)
            handler.close()
        # check we wrote exactly those bytes, ignoring trailing \n etc
        s = stream.getvalue()
        #Compare against what the data should be when encoded in CP-1251
        self.assertEqual(s, '\xe4\xee \xf1\xe2\xe8\xe4\xe0\xed\xe8\xff\n')


# Set the locale to the platform-dependent default.  I have no idea
# why the test does this, but in any case we save the current locale
# first and restore it at the end.
@run_with_locale('LC_ALL', '')
def test_main():
    run_unittest(BuiltinLevelsTest, BasicFilterTest,
                    CustomLevelsAndFiltersTest, MemoryHandlerTest,
                    ConfigFileTest, SocketHandlerTest, MemoryTest,
                    EncodingTest)

if __name__ == "__main__":
    test_main()