Package list logbook / debian/1.5.3-4 logbook / handlers.py
debian/1.5.3-4

Tree @debian/1.5.3-4 (Download .tar.gz)

handlers.py @debian/1.5.3-4raw · history · blame

   1
   2
   3
   4
   5
   6
   7
   8
   9
  10
  11
  12
  13
  14
  15
  16
  17
  18
  19
  20
  21
  22
  23
  24
  25
  26
  27
  28
  29
  30
  31
  32
  33
  34
  35
  36
  37
  38
  39
  40
  41
  42
  43
  44
  45
  46
  47
  48
  49
  50
  51
  52
  53
  54
  55
  56
  57
  58
  59
  60
  61
  62
  63
  64
  65
  66
  67
  68
  69
  70
  71
  72
  73
  74
  75
  76
  77
  78
  79
  80
  81
  82
  83
  84
  85
  86
  87
  88
  89
  90
  91
  92
  93
  94
  95
  96
  97
  98
  99
 100
 101
 102
 103
 104
 105
 106
 107
 108
 109
 110
 111
 112
 113
 114
 115
 116
 117
 118
 119
 120
 121
 122
 123
 124
 125
 126
 127
 128
 129
 130
 131
 132
 133
 134
 135
 136
 137
 138
 139
 140
 141
 142
 143
 144
 145
 146
 147
 148
 149
 150
 151
 152
 153
 154
 155
 156
 157
 158
 159
 160
 161
 162
 163
 164
 165
 166
 167
 168
 169
 170
 171
 172
 173
 174
 175
 176
 177
 178
 179
 180
 181
 182
 183
 184
 185
 186
 187
 188
 189
 190
 191
 192
 193
 194
 195
 196
 197
 198
 199
 200
 201
 202
 203
 204
 205
 206
 207
 208
 209
 210
 211
 212
 213
 214
 215
 216
 217
 218
 219
 220
 221
 222
 223
 224
 225
 226
 227
 228
 229
 230
 231
 232
 233
 234
 235
 236
 237
 238
 239
 240
 241
 242
 243
 244
 245
 246
 247
 248
 249
 250
 251
 252
 253
 254
 255
 256
 257
 258
 259
 260
 261
 262
 263
 264
 265
 266
 267
 268
 269
 270
 271
 272
 273
 274
 275
 276
 277
 278
 279
 280
 281
 282
 283
 284
 285
 286
 287
 288
 289
 290
 291
 292
 293
 294
 295
 296
 297
 298
 299
 300
 301
 302
 303
 304
 305
 306
 307
 308
 309
 310
 311
 312
 313
 314
 315
 316
 317
 318
 319
 320
 321
 322
 323
 324
 325
 326
 327
 328
 329
 330
 331
 332
 333
 334
 335
 336
 337
 338
 339
 340
 341
 342
 343
 344
 345
 346
 347
 348
 349
 350
 351
 352
 353
 354
 355
 356
 357
 358
 359
 360
 361
 362
 363
 364
 365
 366
 367
 368
 369
 370
 371
 372
 373
 374
 375
 376
 377
 378
 379
 380
 381
 382
 383
 384
 385
 386
 387
 388
 389
 390
 391
 392
 393
 394
 395
 396
 397
 398
 399
 400
 401
 402
 403
 404
 405
 406
 407
 408
 409
 410
 411
 412
 413
 414
 415
 416
 417
 418
 419
 420
 421
 422
 423
 424
 425
 426
 427
 428
 429
 430
 431
 432
 433
 434
 435
 436
 437
 438
 439
 440
 441
 442
 443
 444
 445
 446
 447
 448
 449
 450
 451
 452
 453
 454
 455
 456
 457
 458
 459
 460
 461
 462
 463
 464
 465
 466
 467
 468
 469
 470
 471
 472
 473
 474
 475
 476
 477
 478
 479
 480
 481
 482
 483
 484
 485
 486
 487
 488
 489
 490
 491
 492
 493
 494
 495
 496
 497
 498
 499
 500
 501
 502
 503
 504
 505
 506
 507
 508
 509
 510
 511
 512
 513
 514
 515
 516
 517
 518
 519
 520
 521
 522
 523
 524
 525
 526
 527
 528
 529
 530
 531
 532
 533
 534
 535
 536
 537
 538
 539
 540
 541
 542
 543
 544
 545
 546
 547
 548
 549
 550
 551
 552
 553
 554
 555
 556
 557
 558
 559
 560
 561
 562
 563
 564
 565
 566
 567
 568
 569
 570
 571
 572
 573
 574
 575
 576
 577
 578
 579
 580
 581
 582
 583
 584
 585
 586
 587
 588
 589
 590
 591
 592
 593
 594
 595
 596
 597
 598
 599
 600
 601
 602
 603
 604
 605
 606
 607
 608
 609
 610
 611
 612
 613
 614
 615
 616
 617
 618
 619
 620
 621
 622
 623
 624
 625
 626
 627
 628
 629
 630
 631
 632
 633
 634
 635
 636
 637
 638
 639
 640
 641
 642
 643
 644
 645
 646
 647
 648
 649
 650
 651
 652
 653
 654
 655
 656
 657
 658
 659
 660
 661
 662
 663
 664
 665
 666
 667
 668
 669
 670
 671
 672
 673
 674
 675
 676
 677
 678
 679
 680
 681
 682
 683
 684
 685
 686
 687
 688
 689
 690
 691
 692
 693
 694
 695
 696
 697
 698
 699
 700
 701
 702
 703
 704
 705
 706
 707
 708
 709
 710
 711
 712
 713
 714
 715
 716
 717
 718
 719
 720
 721
 722
 723
 724
 725
 726
 727
 728
 729
 730
 731
 732
 733
 734
 735
 736
 737
 738
 739
 740
 741
 742
 743
 744
 745
 746
 747
 748
 749
 750
 751
 752
 753
 754
 755
 756
 757
 758
 759
 760
 761
 762
 763
 764
 765
 766
 767
 768
 769
 770
 771
 772
 773
 774
 775
 776
 777
 778
 779
 780
 781
 782
 783
 784
 785
 786
 787
 788
 789
 790
 791
 792
 793
 794
 795
 796
 797
 798
 799
 800
 801
 802
 803
 804
 805
 806
 807
 808
 809
 810
 811
 812
 813
 814
 815
 816
 817
 818
 819
 820
 821
 822
 823
 824
 825
 826
 827
 828
 829
 830
 831
 832
 833
 834
 835
 836
 837
 838
 839
 840
 841
 842
 843
 844
 845
 846
 847
 848
 849
 850
 851
 852
 853
 854
 855
 856
 857
 858
 859
 860
 861
 862
 863
 864
 865
 866
 867
 868
 869
 870
 871
 872
 873
 874
 875
 876
 877
 878
 879
 880
 881
 882
 883
 884
 885
 886
 887
 888
 889
 890
 891
 892
 893
 894
 895
 896
 897
 898
 899
 900
 901
 902
 903
 904
 905
 906
 907
 908
 909
 910
 911
 912
 913
 914
 915
 916
 917
 918
 919
 920
 921
 922
 923
 924
 925
 926
 927
 928
 929
 930
 931
 932
 933
 934
 935
 936
 937
 938
 939
 940
 941
 942
 943
 944
 945
 946
 947
 948
 949
 950
 951
 952
 953
 954
 955
 956
 957
 958
 959
 960
 961
 962
 963
 964
 965
 966
 967
 968
 969
 970
 971
 972
 973
 974
 975
 976
 977
 978
 979
 980
 981
 982
 983
 984
 985
 986
 987
 988
 989
 990
 991
 992
 993
 994
 995
 996
 997
 998
 999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
# -*- coding: utf-8 -*-
"""
    logbook.handlers
    ~~~~~~~~~~~~~~~~

    The handler interface and builtin handlers.

    :copyright: (c) 2010 by Armin Ronacher, Georg Brandl.
    :license: BSD, see LICENSE for more details.
"""
import io
import os
import re
import sys
import stat
import errno
import socket
import gzip
import math
try:
    from hashlib import sha1
except ImportError:
    from sha import new as sha1
import traceback
import collections
from datetime import datetime, timedelta
from collections import deque
from textwrap import dedent

from logbook.base import (
    CRITICAL, ERROR, WARNING, NOTICE, INFO, DEBUG, TRACE, NOTSET, level_name_property,
    _missing, lookup_level, Flags, ContextObject, ContextStackManager,
    _datetime_factory)
from logbook.helpers import (
    rename, b, _is_text_stream, is_unicode, PY2, zip, xrange, string_types, collections_abc,
    integer_types, reraise, u, with_metaclass)
from logbook.concurrency import new_fine_grained_lock

DEFAULT_FORMAT_STRING = u(
    '[{record.time:%Y-%m-%d %H:%M:%S.%f%z}] '
    '{record.level_name}: {record.channel}: {record.message}')

SYSLOG_FORMAT_STRING = u('{record.channel}: {record.message}')
NTLOG_FORMAT_STRING = dedent(u('''
    Message Level: {record.level_name}
    Location: {record.filename}:{record.lineno}
    Module: {record.module}
    Function: {record.func_name}
    Exact Time: {record.time:%Y-%m-%d %H:%M:%S}

    Event provided Message:

    {record.message}
    ''')).lstrip()

TEST_FORMAT_STRING = u('[{record.level_name}] {record.channel}: {record.message}')
MAIL_FORMAT_STRING = dedent(u('''
    Subject: {handler.subject}

    Message type:       {record.level_name}
    Location:           {record.filename}:{record.lineno}
    Module:             {record.module}
    Function:           {record.func_name}
    Time:               {record.time:%Y-%m-%d %H:%M:%S}

    Message:

    {record.message}
    ''')).lstrip()

MAIL_RELATED_FORMAT_STRING = dedent(u('''
    Message type:       {record.level_name}
    Location:           {record.filename}:{record.lineno}
    Module:             {record.module}
    Function:           {record.func_name}
    {record.message}
    ''')).lstrip()

SYSLOG_PORT = 514

REGTYPE = type(re.compile("I'm a regular expression!"))


def create_syshandler(application_name, level=NOTSET):
    """Creates the handler the operating system provides.  On Unix systems
    this creates a :class:`SyslogHandler`, on Windows sytems it will
    create a :class:`NTEventLogHandler`.
    """
    if os.name == 'nt':
        return NTEventLogHandler(application_name, level=level)
    return SyslogHandler(application_name, level=level)


class _HandlerType(type):
    """The metaclass of handlers injects a destructor if the class has an
    overridden close method.  This makes it possible that the default
    handler class as well as all subclasses that don't need cleanup to be
    collected with less overhead.
    """

    def __new__(cls, name, bases, d):
        # aha, that thing has a custom close method.  We will need a magic
        # __del__ for it to be called on cleanup.
        if (bases != (ContextObject,) and 'close' in d and '__del__' not in d
                and not any(hasattr(x, '__del__') for x in bases)):
            def _magic_del(self):
                try:
                    self.close()
                except Exception:
                    # del is also invoked when init fails, so we better just
                    # ignore any exception that might be raised here
                    pass
            d['__del__'] = _magic_del
        return type.__new__(cls, name, bases, d)


class Handler(with_metaclass(_HandlerType), ContextObject):
    """Handler instances dispatch logging events to specific destinations.

    The base handler class. Acts as a placeholder which defines the Handler
    interface. Handlers can optionally use Formatter instances to format
    records as desired. By default, no formatter is specified; in this case,
    the 'raw' message as determined by record.message is logged.

    To bind a handler you can use the :meth:`push_application`,
    :meth:`push_thread` or :meth:`push_greenlet` methods.
    This will push the handler on a stack of handlers.
    To undo this, use the :meth:`pop_application`,
    :meth:`pop_thread` methods and :meth:`pop_greenlet`::

        handler = MyHandler()
        handler.push_application()
        # all here goes to that handler
        handler.pop_application()

    By default messages sent to that handler will not go to a handler on
    an outer level on the stack, if handled.  This can be changed by
    setting bubbling to `True`.

    There are also context managers to setup the handler for the duration
    of a `with`-block::

        with handler.applicationbound():
            ...

        with handler.threadbound():
            ...

        with handler.greenletbound():
            ...

    Because `threadbound` is a common operation, it is aliased to a with
    on the handler itself if not using gevent::

        with handler:
            ...

    If gevent is enabled, the handler is aliased to `greenletbound`.
    """
    stack_manager = ContextStackManager()

    #: a flag for this handler that can be set to `True` for handlers that
    #: are consuming log records but are not actually displaying it.  This
    #: flag is set for the :class:`NullHandler` for instance.
    blackhole = False

    def __init__(self, level=NOTSET, filter=None, bubble=False):
        #: the level for the handler.  Defaults to `NOTSET` which
        #: consumes all entries.
        self.level = lookup_level(level)
        #: the formatter to be used on records.  This is a function
        #: that is passed a log record as first argument and the
        #: handler as second and returns something formatted
        #: (usually a unicode string)
        self.formatter = None
        #: the filter to be used with this handler
        self.filter = filter
        #: the bubble flag of this handler
        self.bubble = bubble

    level_name = level_name_property()

    def format(self, record):
        """Formats a record with the given formatter.  If no formatter
        is set, the record message is returned.  Generally speaking the
        return value is most likely a unicode string, but nothing in
        the handler interface requires a formatter to return a unicode
        string.

        The combination of a handler and formatter might have the
        formatter return an XML element tree for example.
        """
        if self.formatter is None:
            return record.message
        return self.formatter(record, self)

    def should_handle(self, record):
        """Returns `True` if this handler wants to handle the record.  The
        default implementation checks the level.
        """
        return record.level >= self.level

    def handle(self, record):
        """Emits the record and falls back.  It tries to :meth:`emit` the
        record and if that fails, it will call into :meth:`handle_error` with
        the record and traceback.  This function itself will always emit
        when called, even if the logger level is higher than the record's
        level.

        If this method returns `False` it signals to the calling function that
        no recording took place in which case it will automatically bubble.
        This should not be used to signal error situations.  The default
        implementation always returns `True`.
        """
        try:
            self.emit(record)
        except Exception:
            self.handle_error(record, sys.exc_info())
        return True

    def emit(self, record):
        """Emit the specified logging record.  This should take the
        record and deliver it to whereever the handler sends formatted
        log records.
        """

    def emit_batch(self, records, reason):
        """Some handlers may internally queue up records and want to forward
        them at once to another handler.  For example the
        :class:`~logbook.FingersCrossedHandler` internally buffers
        records until a level threshold is reached in which case the buffer
        is sent to this method and not :meth:`emit` for each record.

        The default behaviour is to call :meth:`emit` for each record in
        the buffer, but handlers can use this to optimize log handling.  For
        instance the mail handler will try to batch up items into one mail
        and not to emit mails for each record in the buffer.

        Note that unlike :meth:`emit` there is no wrapper method like
        :meth:`handle` that does error handling.  The reason is that this
        is intended to be used by other handlers which are already protected
        against internal breakage.

        `reason` is a string that specifies the rason why :meth:`emit_batch`
        was called, and not :meth:`emit`.  The following are valid values:

        ``'buffer'``
            Records were buffered for performance reasons or because the
            records were sent to another process and buffering was the only
            possible way.  For most handlers this should be equivalent to
            calling :meth:`emit` for each record.

        ``'escalation'``
            Escalation means that records were buffered in case the threshold
            was exceeded.  In this case, the last record in the iterable is the
            record that triggered the call.

        ``'group'``
            All the records in the iterable belong to the same logical
            component and happened in the same process.  For example there was
            a long running computation and the handler is invoked with a bunch
            of records that happened there.  This is similar to the escalation
            reason, just that the first one is the significant one, not the
            last.

        If a subclass overrides this and does not want to handle a specific
        reason it must call into the superclass because more reasons might
        appear in future releases.

        Example implementation::

            def emit_batch(self, records, reason):
                if reason not in ('escalation', 'group'):
                    Handler.emit_batch(self, records, reason)
                ...
        """
        for record in records:
            self.emit(record)

    def close(self):
        """Tidy up any resources used by the handler.  This is automatically
        called by the destructor of the class as well, but explicit calls are
        encouraged.  Make sure that multiple calls to close are possible.
        """

    def handle_error(self, record, exc_info):
        """Handle errors which occur during an emit() call.  The behaviour of
        this function depends on the current `errors` setting.

        Check :class:`Flags` for more information.
        """
        try:
            behaviour = Flags.get_flag('errors', 'print')
            if behaviour == 'raise':
                reraise(exc_info[0], exc_info[1], exc_info[2])
            elif behaviour == 'print':
                traceback.print_exception(*(exc_info + (None, sys.stderr)))
                sys.stderr.write('Logged from file %s, line %s\n' % (
                                 record.filename, record.lineno))
        except IOError:
            pass


class NullHandler(Handler):
    """A handler that does nothing.

    Useful to silence logs above a certain location in the handler stack::

        handler = NullHandler()
        handler.push_application()

    NullHandlers swallow all logs sent to them, and do not bubble them onwards.

    """
    blackhole = True

    def __init__(self, level=NOTSET, filter=None):
        super(NullHandler, self).__init__(level=level, filter=filter,
                                          bubble=False)


class WrapperHandler(Handler):
    """A class that can wrap another handler and redirect all calls to the
    wrapped handler::

        handler = WrapperHandler(other_handler)

    Subclasses should override the :attr:`_direct_attrs` attribute as
    necessary.
    """

    #: a set of direct attributes that are not forwarded to the inner
    #: handler.  This has to be extended as necessary.
    _direct_attrs = frozenset(['handler'])

    def __init__(self, handler):
        self.handler = handler

    def __getattr__(self, name):
        return getattr(self.handler, name)

    def __setattr__(self, name, value):
        if name in self._direct_attrs:
            return Handler.__setattr__(self, name, value)
        setattr(self.handler, name, value)


class StringFormatter(object):
    """Many handlers format the log entries to text format.  This is done
    by a callable that is passed a log record and returns an unicode
    string.  The default formatter for this is implemented as a class so
    that it becomes possible to hook into every aspect of the formatting
    process.
    """

    def __init__(self, format_string):
        self.format_string = format_string

    def _get_format_string(self):
        return self._format_string

    def _set_format_string(self, value):
        self._format_string = value
        self._formatter = value

    format_string = property(_get_format_string, _set_format_string)
    del _get_format_string, _set_format_string

    def format_record(self, record, handler):
        try:
            return self._formatter.format(record=record, handler=handler)
        except UnicodeEncodeError:
            # self._formatter is a str, but some of the record items
            # are unicode
            fmt = self._formatter.decode('ascii', 'replace')
            return fmt.format(record=record, handler=handler)
        except UnicodeDecodeError:
            # self._formatter is unicode, but some of the record items
            # are non-ascii str
            fmt = self._formatter.encode('ascii', 'replace')
            return fmt.format(record=record, handler=handler)

    def format_exception(self, record):
        return record.formatted_exception

    def __call__(self, record, handler):
        line = self.format_record(record, handler)
        exc = self.format_exception(record)
        if exc:
            line += u('\n') + exc
        return line


class StringFormatterHandlerMixin(object):
    """A mixin for handlers that provides a default integration for the
    :class:`~logbook.StringFormatter` class.  This is used for all handlers
    by default that log text to a destination.
    """

    #: a class attribute for the default format string to use if the
    #: constructor was invoked with `None`.
    default_format_string = DEFAULT_FORMAT_STRING

    #: the class to be used for string formatting
    formatter_class = StringFormatter

    def __init__(self, format_string):
        if format_string is None:
            format_string = self.default_format_string

        #: the currently attached format string as new-style format
        #: string.
        self.format_string = format_string

    def _get_format_string(self):
        if isinstance(self.formatter, StringFormatter):
            return self.formatter.format_string

    def _set_format_string(self, value):
        if value is None:
            self.formatter = None
        else:
            self.formatter = self.formatter_class(value)

    format_string = property(_get_format_string, _set_format_string)
    del _get_format_string, _set_format_string


class HashingHandlerMixin(object):
    """Mixin class for handlers that are hashing records."""

    def hash_record_raw(self, record):
        """Returns a hashlib object with the hash of the record."""
        hash = sha1()
        hash.update(('%d\x00' % record.level).encode('ascii'))
        hash.update((record.channel or u('')).encode('utf-8') + b('\x00'))
        hash.update(record.filename.encode('utf-8') + b('\x00'))
        hash.update(b(str(record.lineno)))
        return hash

    def hash_record(self, record):
        """Returns a hash for a record to keep it apart from other records.
        This is used for the `record_limit` feature.  By default
        The level, channel, filename and location are hashed.

        Calls into :meth:`hash_record_raw`.
        """
        return self.hash_record_raw(record).hexdigest()

_NUMBER_TYPES = integer_types + (float,)


class LimitingHandlerMixin(HashingHandlerMixin):
    """Mixin class for handlers that want to limit emitting records.

    In the default setting it delivers all log records but it can be set up
    to not send more than n mails for the same record each hour to not
    overload an inbox and the network in case a message is triggered multiple
    times a minute.  The following example limits it to 60 mails an hour::

        from datetime import timedelta
        handler = MailHandler(record_limit=1,
                              record_delta=timedelta(minutes=1))
    """

    def __init__(self, record_limit, record_delta):
        self.record_limit = record_limit
        self._limit_lock = new_fine_grained_lock()
        self._record_limits = {}
        if record_delta is None:
            record_delta = timedelta(seconds=60)
        elif isinstance(record_delta, _NUMBER_TYPES):
            record_delta = timedelta(seconds=record_delta)
        self.record_delta = record_delta

    def check_delivery(self, record):
        """Helper function to check if data should be delivered by this
        handler.  It returns a tuple in the form ``(suppression_count,
        allow)``.  The first one is the number of items that were not delivered
        so far, the second is a boolean flag if a delivery should happen now.
        """
        if self.record_limit is None:
            return 0, True
        hash = self.hash_record(record)
        self._limit_lock.acquire()
        try:
            allow_delivery = None
            suppression_count = old_count = 0
            first_count = now = datetime.utcnow()

            if hash in self._record_limits:
                last_count, suppression_count = self._record_limits[hash]
                if last_count + self.record_delta < now:
                    allow_delivery = True
                else:
                    first_count = last_count
                    old_count = suppression_count

            if (not suppression_count and
                    len(self._record_limits) >= self.max_record_cache):
                cache_items = sorted(self._record_limits.items())
                del cache_items[:int(self._record_limits)
                                * self.record_cache_prune]
                self._record_limits = dict(cache_items)

            self._record_limits[hash] = (first_count, old_count + 1)

            if allow_delivery is None:
                allow_delivery = old_count < self.record_limit
            return suppression_count, allow_delivery
        finally:
            self._limit_lock.release()


class StreamHandler(Handler, StringFormatterHandlerMixin):
    """a handler class which writes logging records, appropriately formatted,
    to a stream. note that this class does not close the stream, as sys.stdout
    or sys.stderr may be used.

    If a stream handler is used in a `with` statement directly it will
    :meth:`close` on exit to support this pattern::

        with StreamHandler(my_stream):
            pass

    .. admonition:: Notes on the encoding

       On Python 3, the encoding parameter is only used if a stream was
       passed that was opened in binary mode.
    """

    def __init__(self, stream, level=NOTSET, format_string=None,
                 encoding=None, filter=None, bubble=False):
        Handler.__init__(self, level, filter, bubble)
        StringFormatterHandlerMixin.__init__(self, format_string)
        self.encoding = encoding
        self.lock = new_fine_grained_lock()
        if stream is not _missing:
            self.stream = stream

    def __enter__(self):
        return Handler.__enter__(self)

    def __exit__(self, exc_type, exc_value, tb):
        self.close()
        return Handler.__exit__(self, exc_type, exc_value, tb)

    def ensure_stream_is_open(self):
        """this method should be overriden in sub-classes to ensure that the
        inner stream is open
        """
        pass

    def close(self):
        """The default stream handler implementation is not to close
        the wrapped stream but to flush it.
        """
        self.flush()

    def flush(self):
        """Flushes the inner stream."""
        if self.stream is not None and hasattr(self.stream, 'flush'):
            self.stream.flush()

    def encode(self, msg):
        """Encodes the message to the stream encoding."""
        stream = self.stream
        rv = msg + '\n'
        if ((PY2 and is_unicode(rv)) or
                not (PY2 or is_unicode(rv) or _is_text_stream(stream))):
            enc = self.encoding
            if enc is None:
                enc = getattr(stream, 'encoding', None) or 'utf-8'
            rv = rv.encode(enc, 'replace')
        return rv

    def write(self, item):
        """Writes a bytestring to the stream."""
        self.stream.write(item)

    def emit(self, record):
        msg = self.format(record)
        self.lock.acquire()
        try:
            self.ensure_stream_is_open()
            self.write(self.encode(msg))
            if self.should_flush():
                self.flush()
        finally:
            self.lock.release()

    def should_flush(self):
        return True


class FileHandler(StreamHandler):
    """A handler that does the task of opening and closing files for you.
    By default the file is opened right away, but you can also `delay`
    the open to the point where the first message is written.

    This is useful when the handler is used with a
    :class:`~logbook.FingersCrossedHandler` or something similar.
    """

    def __init__(self, filename, mode='a', encoding=None, level=NOTSET,
                 format_string=None, delay=False, filter=None, bubble=False):
        if encoding is None:
            encoding = 'utf-8'
        StreamHandler.__init__(self, None, level, format_string,
                               encoding, filter, bubble)
        self._filename = filename
        self._mode = mode
        if delay:
            self.stream = None
        else:
            self._open()

    def _open(self, mode=None):
        if mode is None:
            mode = self._mode
        self.stream = io.open(self._filename, mode, encoding=self.encoding)

    def write(self, item):
        self.ensure_stream_is_open()
        if isinstance(item, bytes):
            self.stream.buffer.write(item)
        else:
            self.stream.write(item)

    def close(self):
        self.lock.acquire()
        try:
            if self.stream is not None:
                self.flush()
                self.stream.close()
                self.stream = None
        finally:
            self.lock.release()

    def encode(self, record):
        # encodes based on the stream settings, so the stream has to be
        # open at the time this function is called.
        self.ensure_stream_is_open()
        return StreamHandler.encode(self, record)

    def ensure_stream_is_open(self):
        if self.stream is None:
            self._open()


class GZIPCompressionHandler(FileHandler):
    def __init__(self, filename, encoding=None, level=NOTSET,
                 format_string=None, delay=False, filter=None, bubble=False, compression_quality=9):

        self._compression_quality = compression_quality
        super(GZIPCompressionHandler, self).__init__(filename, mode='wb', encoding=encoding, level=level,
                             format_string=format_string, delay=delay, filter=filter, bubble=bubble)

    def _open(self, mode=None):
        if mode is None:
            mode = self._mode
        self.stream = gzip.open(self._filename, mode, compresslevel=self._compression_quality)

    def write(self, item):
        if isinstance(item, str):
            item = item.encode(encoding=self.encoding)
        self.ensure_stream_is_open()
        self.stream.write(item)

    def should_flush(self):
        # gzip manages writes independently. Flushing prematurely could mean
        # duplicate flushes and thus bloated files
        return False


class BrotliCompressionHandler(FileHandler):
    def __init__(self, filename, encoding=None, level=NOTSET,
                 format_string=None, delay=False, filter=None, bubble=False,
                 compression_window_size=4*1024**2, compression_quality=11):
        super(BrotliCompressionHandler, self).__init__(filename, mode='wb', encoding=encoding, level=level,
                             format_string=format_string, delay=delay, filter=filter, bubble=bubble)
        try:
            from brotli import Compressor
        except ImportError:
            raise RuntimeError('The brotli library is required for '
                               'the BrotliCompressionHandler.')

        max_window_size = int(math.log(compression_window_size, 2))
        self._compressor = Compressor(quality=compression_quality, lgwin=max_window_size)

    def _open(self, mode=None):
        if mode is None:
            mode = self._mode
        self.stream = io.open(self._filename, mode)

    def write(self, item):
        if isinstance(item, str):
            item = item.encode(encoding=self.encoding)
        ret = self._compressor.process(item)
        if ret:
            self.ensure_stream_is_open()
            self.stream.write(ret)
            super(BrotliCompressionHandler, self).flush()

    def should_flush(self):
        return False

    def flush(self):
        if self._compressor is not None:
            ret = self._compressor.flush()
            if ret:
                self.ensure_stream_is_open()
                self.stream.write(ret)
        super(BrotliCompressionHandler, self).flush()

    def close(self):
        if self._compressor is not None:
            self.ensure_stream_is_open()
            self.stream.write(self._compressor.finish())
            self._compressor = None
        super(BrotliCompressionHandler, self).close()


class MonitoringFileHandler(FileHandler):
    """A file handler that will check if the file was moved while it was
    open.  This might happen on POSIX systems if an application like
    logrotate moves the logfile over.

    Because of different IO concepts on Windows, this handler will not
    work on a windows system.
    """

    def __init__(self, filename, mode='a', encoding='utf-8', level=NOTSET,
                 format_string=None, delay=False, filter=None, bubble=False):
        FileHandler.__init__(self, filename, mode, encoding, level,
                             format_string, delay, filter, bubble)
        if os.name == 'nt':
            raise RuntimeError('MonitoringFileHandler '
                               'does not support Windows')
        self._query_fd()

    def _query_fd(self):
        if self.stream is None:
            self._last_stat = None, None
        else:
            try:
                st = os.stat(self._filename)
            except OSError:
                e = sys.exc_info()[1]
                if e.errno != errno.ENOENT:
                    raise
                self._last_stat = None, None
            else:
                self._last_stat = st[stat.ST_DEV], st[stat.ST_INO]

    def emit(self, record):
        msg = self.format(record)
        self.lock.acquire()
        try:
            last_stat = self._last_stat
            self._query_fd()
            if last_stat != self._last_stat and self.stream is not None:
                self.flush()
                self.stream.close()
                self.stream = None
            self.ensure_stream_is_open()
            self.write(self.encode(msg))
            self.flush()
            self._query_fd()
        finally:
            self.lock.release()


class StderrHandler(StreamHandler):
    """A handler that writes to what is currently at stderr.  At the first
    glace this appears to just be a :class:`StreamHandler` with the stream
    set to :data:`sys.stderr` but there is a difference: if the handler is
    created globally and :data:`sys.stderr` changes later, this handler will
    point to the current `stderr`, whereas a stream handler would still
    point to the old one.
    """

    def __init__(self, level=NOTSET, format_string=None, filter=None,
                 bubble=False):
        StreamHandler.__init__(self, _missing, level, format_string,
                               None, filter, bubble)

    @property
    def stream(self):
        return sys.stderr


class RotatingFileHandler(FileHandler):
    """This handler rotates based on file size.  Once the maximum size
    is reached it will reopen the file and start with an empty file
    again.  The old file is moved into a backup copy (named like the
    file, but with a ``.backupnumber`` appended to the file.  So if
    you are logging to ``mail`` the first backup copy is called
    ``mail.1``.)

    The default number of backups is 5.  Unlike a similar logger from
    the logging package, the backup count is mandatory because just
    reopening the file is dangerous as it deletes the log without
    asking on rollover.
    """

    def __init__(self, filename, mode='a', encoding='utf-8', level=NOTSET,
                 format_string=None, delay=False, max_size=1024 * 1024,
                 backup_count=5, filter=None, bubble=False):
        FileHandler.__init__(self, filename, mode, encoding, level,
                             format_string, delay, filter, bubble)
        self.max_size = max_size
        self.backup_count = backup_count
        assert backup_count > 0, ('at least one backup file has to be '
                                  'specified')

    def should_rollover(self, record, bytes):
        self.stream.seek(0, 2)
        return self.stream.tell() + bytes >= self.max_size

    def perform_rollover(self):
        self.stream.close()
        for x in xrange(self.backup_count - 1, 0, -1):
            src = '%s.%d' % (self._filename, x)
            dst = '%s.%d' % (self._filename, x + 1)
            try:
                rename(src, dst)
            except OSError:
                e = sys.exc_info()[1]
                if e.errno != errno.ENOENT:
                    raise
        rename(self._filename, self._filename + '.1')
        self._open('w')

    def emit(self, record):
        msg = self.format(record)
        self.lock.acquire()
        try:
            msg = self.encode(msg)
            if self.should_rollover(record, len(msg)):
                self.perform_rollover()
            self.write(msg)
            self.flush()
        finally:
            self.lock.release()


class TimedRotatingFileHandler(FileHandler):
    """This handler rotates based on dates.  It will name the file
    after the filename you specify and the `date_format` pattern.

    So for example if you configure your handler like this::

        handler = TimedRotatingFileHandler('/var/log/foo.log',
                                           date_format='%Y-%m-%d')

    The filenames for the logfiles will look like this::

        /var/log/foo-2010-01-10.log
        /var/log/foo-2010-01-11.log
        ...

    By default it will keep all these files around, if you want to limit
    them, you can specify a `backup_count`.

    You may supply an optional `rollover_format`. This allows you to specify
    the format for the filenames of rolled-over files.
    the format as

    So for example if you configure your handler like this::

        handler = TimedRotatingFileHandler(
            '/var/log/foo.log',
            date_format='%Y-%m-%d',
            rollover_format='{basename}{ext}.{timestamp}')

    The filenames for the logfiles will look like this::

        /var/log/foo.log.2010-01-10
        /var/log/foo.log.2010-01-11
        ...

    Finally, an optional argument `timed_filename_for_current` may be set to
    false if you wish to have the current log file match the supplied filename
    until it is rolled over
    """

    def __init__(self, filename, mode='a', encoding='utf-8', level=NOTSET,
                 format_string=None, date_format='%Y-%m-%d',
                 backup_count=0, filter=None, bubble=False,
                 timed_filename_for_current=True,
                 rollover_format='{basename}-{timestamp}{ext}'):
        self.date_format = date_format
        self.backup_count = backup_count

        self.rollover_format = rollover_format

        self.original_filename = filename
        self.basename, self.ext = os.path.splitext(os.path.abspath(filename))
        self.timed_filename_for_current = timed_filename_for_current

        self._timestamp = self._get_timestamp(_datetime_factory())
        if self.timed_filename_for_current:
            filename = self.generate_timed_filename(self._timestamp)
        elif os.path.exists(filename):
            self._timestamp = self._get_timestamp(
                datetime.fromtimestamp(
                    os.stat(filename).st_mtime
                )
            )

        FileHandler.__init__(self, filename, mode, encoding, level,
                             format_string, True, filter, bubble)

    def _get_timestamp(self, datetime):
        """
        Fetches a formatted string witha timestamp of the given datetime
        """
        return datetime.strftime(self.date_format)

    def generate_timed_filename(self, timestamp):
        """
        Produces a filename that includes a timestamp in the format supplied
        to the handler at init time.
        """
        timed_filename = self.rollover_format.format(
            basename=self.basename,
            timestamp=timestamp,
            ext=self.ext)
        return timed_filename

    def files_to_delete(self):
        """Returns a list with the files that have to be deleted when
        a rollover occours.
        """
        directory = os.path.dirname(self._filename)
        files = []
        rollover_regex = re.compile(self.rollover_format.format(
            basename=re.escape(self.basename),
            timestamp='.+',
            ext=re.escape(self.ext),
        ))
        for filename in os.listdir(directory):
            filename = os.path.join(directory, filename)
            if rollover_regex.match(filename):
                files.append((os.path.getmtime(filename), filename))
        files.sort()
        if self.backup_count > 1:
            return files[:-self.backup_count + 1]
        else:
            return files[:]

    def perform_rollover(self, new_timestamp):
        if self.stream is not None:
            self.stream.close()

        if (
                not self.timed_filename_for_current
                and os.path.exists(self._filename)
        ):
            filename = self.generate_timed_filename(self._timestamp)
            os.rename(self._filename, filename)

        if self.backup_count > 0:
            for time, filename in self.files_to_delete():
                os.remove(filename)

        if self.timed_filename_for_current:
            self._filename = self.generate_timed_filename(new_timestamp)
        self._timestamp = new_timestamp

        self._open('w')

    def emit(self, record):
        msg = self.format(record)
        self.lock.acquire()
        try:
            new_timestamp = self._get_timestamp(record.time)
            if new_timestamp != self._timestamp:
                self.perform_rollover(new_timestamp)
            self.write(self.encode(msg))
            self.flush()
        finally:
            self.lock.release()


class TestHandler(Handler, StringFormatterHandlerMixin):
    """Like a stream handler but keeps the values in memory.  This
    logger provides some ways to test for the records in memory.

    Example usage::

        def my_test():
            with logbook.TestHandler() as handler:
                logger.warn('A warning')
                assert logger.has_warning('A warning')
                ...
    """
    default_format_string = TEST_FORMAT_STRING

    def __init__(self, level=NOTSET, format_string=None, filter=None,
                 bubble=False, force_heavy_init=False):
        Handler.__init__(self, level, filter, bubble)
        StringFormatterHandlerMixin.__init__(self, format_string)
        #: captures the :class:`LogRecord`\s as instances
        self.records = []
        self._formatted_records = []
        self._formatted_record_cache = []
        self._force_heavy_init = force_heavy_init

    def close(self):
        """Close all records down when the handler is closed."""
        for record in self.records:
            record.close()

    def emit(self, record):
        # keep records open because we will want to examine them after the
        # call to the emit function.  If we don't do that, the traceback
        # attribute and other things will already be removed.
        record.keep_open = True
        if self._force_heavy_init:
            record.heavy_init()
        self.records.append(record)

    @property
    def formatted_records(self):
        """Captures the formatted log records as unicode strings."""
        if (len(self._formatted_record_cache) != len(self.records) or
                any(r1 != r2 for r1, r2 in
                    zip(self.records, self._formatted_record_cache))):
            self._formatted_records = [self.format(r) for r in self.records]
            self._formatted_record_cache = list(self.records)
        return self._formatted_records

    @property
    def has_criticals(self):
        """`True` if any :data:`CRITICAL` records were found."""
        return any(r.level == CRITICAL for r in self.records)

    @property
    def has_errors(self):
        """`True` if any :data:`ERROR` records were found."""
        return any(r.level == ERROR for r in self.records)

    @property
    def has_warnings(self):
        """`True` if any :data:`WARNING` records were found."""
        return any(r.level == WARNING for r in self.records)

    @property
    def has_notices(self):
        """`True` if any :data:`NOTICE` records were found."""
        return any(r.level == NOTICE for r in self.records)

    @property
    def has_infos(self):
        """`True` if any :data:`INFO` records were found."""
        return any(r.level == INFO for r in self.records)

    @property
    def has_debugs(self):
        """`True` if any :data:`DEBUG` records were found."""
        return any(r.level == DEBUG for r in self.records)

    @property
    def has_traces(self):
        """`True` if any :data:`TRACE` records were found."""
        return any(r.level == TRACE for r in self.records)

    def has_critical(self, *args, **kwargs):
        """`True` if a specific :data:`CRITICAL` log record exists.

        See :ref:`probe-log-records` for more information.
        """
        kwargs['level'] = CRITICAL
        return self._test_for(*args, **kwargs)

    def has_error(self, *args, **kwargs):
        """`True` if a specific :data:`ERROR` log record exists.

        See :ref:`probe-log-records` for more information.
        """
        kwargs['level'] = ERROR
        return self._test_for(*args, **kwargs)

    def has_warning(self, *args, **kwargs):
        """`True` if a specific :data:`WARNING` log record exists.

        See :ref:`probe-log-records` for more information.
        """
        kwargs['level'] = WARNING
        return self._test_for(*args, **kwargs)

    def has_notice(self, *args, **kwargs):
        """`True` if a specific :data:`NOTICE` log record exists.

        See :ref:`probe-log-records` for more information.
        """
        kwargs['level'] = NOTICE
        return self._test_for(*args, **kwargs)

    def has_info(self, *args, **kwargs):
        """`True` if a specific :data:`INFO` log record exists.

        See :ref:`probe-log-records` for more information.
        """
        kwargs['level'] = INFO
        return self._test_for(*args, **kwargs)

    def has_debug(self, *args, **kwargs):
        """`True` if a specific :data:`DEBUG` log record exists.

        See :ref:`probe-log-records` for more information.
        """
        kwargs['level'] = DEBUG
        return self._test_for(*args, **kwargs)

    def has_trace(self, *args, **kwargs):
        """`True` if a specific :data:`TRACE` log record exists.

        See :ref:`probe-log-records` for more information.
        """
        kwargs['level'] = TRACE
        return self._test_for(*args, **kwargs)

    def _test_for(self, message=None, channel=None, level=None):
        def _match(needle, haystack):
            """Matches both compiled regular expressions and strings"""
            if isinstance(needle, REGTYPE) and needle.search(haystack):
                return True
            if needle == haystack:
                return True
            return False
        for record in self.records:
            if level is not None and record.level != level:
                continue
            if channel is not None and record.channel != channel:
                continue
            if message is not None and not _match(message, record.message):
                continue
            return True
        return False


class MailHandler(Handler, StringFormatterHandlerMixin,
                  LimitingHandlerMixin):
    """A handler that sends error mails.  The format string used by this
    handler are the contents of the mail plus the headers.  This is handy
    if you want to use a custom subject or ``X-`` header::

        handler = MailHandler(format_string='''\
        Subject: {record.level_name} on My Application

        {record.message}
        {record.extra[a_custom_injected_record]}
        ''')

    This handler will always emit text-only mails for maximum portability and
    best performance.

    In the default setting it delivers all log records but it can be set up
    to not send more than n mails for the same record each hour to not
    overload an inbox and the network in case a message is triggered multiple
    times a minute.  The following example limits it to 60 mails an hour::

        from datetime import timedelta
        handler = MailHandler(record_limit=1,
                              record_delta=timedelta(minutes=1))

    The default timedelta is 60 seconds (one minute).

    The mail handler sends mails in a blocking manner.  If you are not
    using some centralized system for logging these messages (with the help
    of ZeroMQ or others) and the logging system slows you down you can
    wrap the handler in a :class:`logbook.queues.ThreadedWrapperHandler`
    that will then send the mails in a background thread.

    `server_addr` can be a tuple of host and port, or just a string containing
    the host to use the default port (25, or 465 if connecting securely.)

    `credentials` can be a tuple or dictionary of arguments that will be passed
    to :py:meth:`smtplib.SMTP.login`.

    `secure` can be a tuple, dictionary, or boolean. As a boolean, this will
    simply enable or disable a secure connection. The tuple is unpacked as
    parameters `keyfile`, `certfile`. As a dictionary, `secure` should contain
    those keys. For backwards compatibility, ``secure=()`` will enable a secure
    connection. If `starttls` is enabled (default), these parameters will be
    passed to :py:meth:`smtplib.SMTP.starttls`, otherwise
    :py:class:`smtplib.SMTP_SSL`.


    .. versionchanged:: 0.3
       The handler supports the batching system now.

    .. versionadded:: 1.0
       `starttls` parameter added to allow disabling STARTTLS for SSL
       connections.

    .. versionchanged:: 1.0
       If `server_addr` is a string, the default port will be used.

    .. versionchanged:: 1.0
       `credentials` parameter can now be a dictionary of keyword arguments.

    .. versionchanged:: 1.0
       `secure` can now be a dictionary or boolean in addition to to a tuple.
    """
    default_format_string = MAIL_FORMAT_STRING
    default_related_format_string = MAIL_RELATED_FORMAT_STRING
    default_subject = u('Server Error in Application')

    #: the maximum number of record hashes in the cache for the limiting
    #: feature.  Afterwards, record_cache_prune percent of the oldest
    #: entries are removed
    max_record_cache = 512

    #: the number of items to prune on a cache overflow in percent.
    record_cache_prune = 0.333

    def __init__(self, from_addr, recipients, subject=None,
                 server_addr=None, credentials=None, secure=None,
                 record_limit=None, record_delta=None, level=NOTSET,
                 format_string=None, related_format_string=None,
                 filter=None, bubble=False, starttls=True):
        Handler.__init__(self, level, filter, bubble)
        StringFormatterHandlerMixin.__init__(self, format_string)
        LimitingHandlerMixin.__init__(self, record_limit, record_delta)
        self.from_addr = from_addr
        self.recipients = recipients
        if subject is None:
            subject = self.default_subject
        self.subject = subject
        self.server_addr = server_addr
        self.credentials = credentials
        self.secure = secure
        if related_format_string is None:
            related_format_string = self.default_related_format_string
        self.related_format_string = related_format_string
        self.starttls = starttls

    def _get_related_format_string(self):
        if isinstance(self.related_formatter, StringFormatter):
            return self.related_formatter.format_string

    def _set_related_format_string(self, value):
        if value is None:
            self.related_formatter = None
        else:
            self.related_formatter = self.formatter_class(value)
    related_format_string = property(_get_related_format_string,
                                     _set_related_format_string)
    del _get_related_format_string, _set_related_format_string

    def get_recipients(self, record):
        """Returns the recipients for a record.  By default the
        :attr:`recipients` attribute is returned for all records.
        """
        return self.recipients

    def message_from_record(self, record, suppressed):
        """Creates a new message for a record as email message object
        (:class:`email.message.Message`).  `suppressed` is the number
        of mails not sent if the `record_limit` feature is active.
        """
        from email.message import Message
        from email.header import Header
        msg = Message()
        msg.set_charset('utf-8')
        lineiter = iter(self.format(record).splitlines())
        for line in lineiter:
            if not line:
                break
            h, v = line.split(':', 1)
            # We could probably just encode everything. For the moment encode
            # only what really needed to avoid breaking a couple of tests.
            try:
                v.encode('ascii')
            except UnicodeEncodeError:
                msg[h.strip()] = Header(v.strip(), 'utf-8')
            else:
                msg[h.strip()] = v.strip()

        msg.replace_header('Content-Transfer-Encoding', '8bit')

        body = '\r\n'.join(lineiter)
        if suppressed:
            body += ('\r\n\r\nThis message occurred additional %d '
                     'time(s) and was suppressed' % suppressed)

        # inconsistency in Python 2.5
        # other versions correctly return msg.get_payload() as str
        if sys.version_info < (2, 6) and isinstance(body, unicode):
            body = body.encode('utf-8')

        msg.set_payload(body, 'UTF-8')
        return msg

    def format_related_record(self, record):
        """Used for format the records that led up to another record or
        records that are related into strings.  Used by the batch formatter.
        """
        return self.related_formatter(record, self)

    def generate_mail(self, record, suppressed=0):
        """Generates the final email (:class:`email.message.Message`)
        with headers and date.  `suppressed` is the number of mails
        that were not send if the `record_limit` feature is active.
        """
        from email.utils import formatdate
        msg = self.message_from_record(record, suppressed)
        msg['From'] = self.from_addr
        msg['Date'] = formatdate()
        return msg

    def collapse_mails(self, mail, related, reason):
        """When escaling or grouped mails are """
        if not related:
            return mail
        if reason == 'group':
            title = 'Other log records in the same group'
        else:
            title = 'Log records that led up to this one'
        mail.set_payload('%s\r\n\r\n\r\n%s:\r\n\r\n%s' % (
            mail.get_payload(),
            title,
            '\r\n\r\n'.join(body.rstrip() for body in related)
        ), 'UTF-8')
        return mail

    def get_connection(self):
        """Returns an SMTP connection.  By default it reconnects for
        each sent mail.
        """
        from smtplib import SMTP, SMTP_SSL, SMTP_PORT, SMTP_SSL_PORT
        if self.server_addr is None:
            host = '127.0.0.1'
            port = self.secure and SMTP_SSL_PORT or SMTP_PORT
        else:
            try:
                host, port = self.server_addr
            except ValueError:
                # If server_addr is a string, the tuple unpacking will raise
                # ValueError, and we can use the default port.
                host = self.server_addr
                port = self.secure and SMTP_SSL_PORT or SMTP_PORT

        # Previously, self.secure was passed as con.starttls(*self.secure). This
        # meant that starttls couldn't be used without a keyfile and certfile
        # unless an empty tuple was passed. See issue #94.
        #
        # The changes below allow passing:
        # - secure=True for secure connection without checking identity.
        # - dictionary with keys 'keyfile' and 'certfile'.
        # - tuple to be unpacked to variables keyfile and certfile.
        # - secure=() equivalent to secure=True for backwards compatibility.
        # - secure=False equivalent to secure=None to disable.
        if isinstance(self.secure, collections_abc.Mapping):
            keyfile = self.secure.get('keyfile', None)
            certfile = self.secure.get('certfile', None)
        elif isinstance(self.secure, collections_abc.Iterable):
            # Allow empty tuple for backwards compatibility
            if len(self.secure) == 0:
                keyfile = certfile = None
            else:
                keyfile, certfile = self.secure
        else:
            keyfile = certfile = None

        # Allow starttls to be disabled by passing starttls=False.
        if not self.starttls and self.secure:
            con = SMTP_SSL(host, port, keyfile=keyfile, certfile=certfile)
        else:
            con = SMTP(host, port)

        if self.credentials is not None:
            secure = self.secure
            if self.starttls and secure is not None and secure is not False:
                con.ehlo()
                con.starttls(keyfile=keyfile, certfile=certfile)
                con.ehlo()

            # Allow credentials to be a tuple or dict.
            if isinstance(self.credentials, collections_abc.Mapping):
                credentials_args = ()
                credentials_kwargs = self.credentials
            else:
                credentials_args = self.credentials
                credentials_kwargs = dict()

            con.login(*credentials_args, **credentials_kwargs)
        return con

    def close_connection(self, con):
        """Closes the connection that was returned by
        :meth:`get_connection`.
        """
        try:
            if con is not None:
                con.quit()
        except Exception:
            pass

    def deliver(self, msg, recipients):
        """Delivers the given message to a list of recipients."""
        con = self.get_connection()
        try:
            con.sendmail(self.from_addr, recipients, msg.as_string())
        finally:
            self.close_connection(con)

    def emit(self, record):
        suppressed = 0
        if self.record_limit is not None:
            suppressed, allow_delivery = self.check_delivery(record)
            if not allow_delivery:
                return
        self.deliver(self.generate_mail(record, suppressed),
                     self.get_recipients(record))

    def emit_batch(self, records, reason):
        if reason not in ('escalation', 'group'):
            raise RuntimeError("reason must be either 'escalation' or 'group'")
        records = list(records)
        if not records:
            return

        trigger = records.pop(reason == 'escalation' and -1 or 0)
        suppressed = 0
        if self.record_limit is not None:
            suppressed, allow_delivery = self.check_delivery(trigger)
            if not allow_delivery:
                return

        trigger_mail = self.generate_mail(trigger, suppressed)
        related = [self.format_related_record(record)
                   for record in records]

        self.deliver(self.collapse_mails(trigger_mail, related, reason),
                     self.get_recipients(trigger))


class GMailHandler(MailHandler):
    """
    A customized mail handler class for sending emails via GMail (or Google
    Apps mail)::

       handler = GMailHandler(
           "my_user@gmail.com", "mypassword", ["to_user@some_mail.com"],
           ...) # other arguments same as MailHandler

    .. versionadded:: 0.6.0
    """

    def __init__(self, account_id, password, recipients, **kw):
        super(GMailHandler, self).__init__(
            account_id, recipients, secure=True,
            server_addr=("smtp.gmail.com", 587),
            credentials=(account_id, password), **kw)


class SyslogHandler(Handler, StringFormatterHandlerMixin):
    """A handler class which sends formatted logging records to a
    syslog server.  By default it will send to it via unix socket.
    """
    default_format_string = SYSLOG_FORMAT_STRING

    # priorities
    LOG_EMERG = 0       # system is unusable
    LOG_ALERT = 1       # action must be taken immediately
    LOG_CRIT = 2       # critical conditions
    LOG_ERR = 3       # error conditions
    LOG_WARNING = 4       # warning conditions
    LOG_NOTICE = 5       # normal but significant condition
    LOG_INFO = 6       # informational
    LOG_DEBUG = 7       # debug-level messages

    # facility codes
    LOG_KERN = 0       # kernel messages
    LOG_USER = 1       # random user-level messages
    LOG_MAIL = 2       # mail system
    LOG_DAEMON = 3       # system daemons
    LOG_AUTH = 4       # security/authorization messages
    LOG_SYSLOG = 5       # messages generated internally by syslogd
    LOG_LPR = 6       # line printer subsystem
    LOG_NEWS = 7       # network news subsystem
    LOG_UUCP = 8       # UUCP subsystem
    LOG_CRON = 9       # clock daemon
    LOG_AUTHPRIV = 10      # security/authorization messages (private)
    LOG_FTP = 11      # FTP daemon

    # other codes through 15 reserved for system use
    LOG_LOCAL0 = 16      # reserved for local use
    LOG_LOCAL1 = 17      # reserved for local use
    LOG_LOCAL2 = 18      # reserved for local use
    LOG_LOCAL3 = 19      # reserved for local use
    LOG_LOCAL4 = 20      # reserved for local use
    LOG_LOCAL5 = 21      # reserved for local use
    LOG_LOCAL6 = 22      # reserved for local use
    LOG_LOCAL7 = 23      # reserved for local use

    facility_names = {
        'auth':     LOG_AUTH,
        'authpriv': LOG_AUTHPRIV,
        'cron':     LOG_CRON,
        'daemon':   LOG_DAEMON,
        'ftp':      LOG_FTP,
        'kern':     LOG_KERN,
        'lpr':      LOG_LPR,
        'mail':     LOG_MAIL,
        'news':     LOG_NEWS,
        'syslog':   LOG_SYSLOG,
        'user':     LOG_USER,
        'uucp':     LOG_UUCP,
        'local0':   LOG_LOCAL0,
        'local1':   LOG_LOCAL1,
        'local2':   LOG_LOCAL2,
        'local3':   LOG_LOCAL3,
        'local4':   LOG_LOCAL4,
        'local5':   LOG_LOCAL5,
        'local6':   LOG_LOCAL6,
        'local7':   LOG_LOCAL7,
    }

    level_priority_map = {
        DEBUG:      LOG_DEBUG,
        INFO:       LOG_INFO,
        NOTICE:     LOG_NOTICE,
        WARNING:    LOG_WARNING,
        ERROR:      LOG_ERR,
        CRITICAL:   LOG_CRIT
    }

    def __init__(self, application_name=None, address=None,
                 facility='user', socktype=socket.SOCK_DGRAM,
                 level=NOTSET, format_string=None, filter=None,
                 bubble=False, record_delimiter=None):
        Handler.__init__(self, level, filter, bubble)
        StringFormatterHandlerMixin.__init__(self, format_string)
        self.application_name = application_name

        if address is None:
            if sys.platform == 'darwin':
                address = '/var/run/syslog'
            else:
                address = '/dev/log'

        self.remote_address = self.address = address
        self.facility = facility
        self.socktype = socktype

        if isinstance(address, string_types):
            self._connect_unixsocket()
            self.enveloper = self.unix_envelope
            default_delimiter = u'\x00'
        else:
            self._connect_netsocket()
            self.enveloper = self.net_envelope
            default_delimiter = u'\n'

        self.record_delimiter = default_delimiter \
            if record_delimiter is None else record_delimiter

        self.connection_exception = getattr(
            __builtins__, 'BrokenPipeError', socket.error)

    def _connect_unixsocket(self):
        self.unixsocket = True
        self.socket = socket.socket(socket.AF_UNIX, socket.SOCK_DGRAM)
        try:
            self.socket.connect(self.address)
        except socket.error:
            self.socket.close()
            self.socket = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
            self.socket.connect(self.address)

    def _connect_netsocket(self):
        self.unixsocket = False
        self.socket = socket.socket(socket.AF_INET, self.socktype)
        if self.socktype == socket.SOCK_STREAM:
            self.socket.connect(self.remote_address)
            self.address = self.socket.getsockname()

    def encode_priority(self, record):
        facility = self.facility_names[self.facility]
        priority = self.level_priority_map.get(record.level,
                                               self.LOG_WARNING)
        return (facility << 3) | priority

    def wrap_segments(self, record, before):
        msg = self.format(record)
        segments = [segment for segment in msg.split(self.record_delimiter)]
        return (before + segment + self.record_delimiter
                for segment in segments)
        
    def unix_envelope(self, record):
        before = u'<{}>{}'.format(
            self.encode_priority(record),
            self.application_name + ':' if self.application_name else '')
        return self.wrap_segments(record, before)

    def net_envelope(self, record):
        # Gross but effective
        try:
            format_string = self.format_string
            application_name = self.application_name
            if not application_name and record.channel and \
               '{record.channel}: ' in format_string:
                self.format_string = format_string.replace(
                    '{record.channel}: ', '')
                self.application_name = record.channel
            # RFC 5424: <PRIVAL>version timestamp hostname app-name procid
            #           msgid structured-data message
            before = u'<{}>1 {}Z {} {} {} - - '.format(
                self.encode_priority(record),
                record.time.isoformat(),
                socket.gethostname(),
                self.application_name if self.application_name else '-',
                record.process)
            return self.wrap_segments(record, before)
        finally:
            self.format_string = format_string
            self.application_name = application_name

    def emit(self, record):
        for segment in self.enveloper(record):
            self.send_to_socket(segment.encode('utf-8'))

    def send_to_socket(self, data):
        if self.unixsocket:
            try:
                self.socket.send(data)
            except socket.error:
                self._connect_unixsocket()
                self.socket.send(data)
        elif self.socktype == socket.SOCK_DGRAM:
            # the flags are no longer optional on Python 3
            self.socket.sendto(data, 0, self.address)
        else:
            try:
                self.socket.sendall(data)
            except self.connection_exception:
                self._connect_netsocket()
                self.socket.send(data)

    def close(self):
        self.socket.close()


class NTEventLogHandler(Handler, StringFormatterHandlerMixin):
    """A handler that sends to the NT event log system."""
    dllname = None
    default_format_string = NTLOG_FORMAT_STRING

    def __init__(self, application_name, log_type='Application',
                 level=NOTSET, format_string=None, filter=None,
                 bubble=False):
        Handler.__init__(self, level, filter, bubble)
        StringFormatterHandlerMixin.__init__(self, format_string)

        if os.name != 'nt':
            raise RuntimeError('NTLogEventLogHandler requires a Windows '
                               'operating system.')

        try:
            import win32evtlogutil
            import win32evtlog
        except ImportError:
            raise RuntimeError('The pywin32 library is required '
                               'for the NTEventLogHandler.')

        self.application_name = application_name
        self._welu = win32evtlogutil
        dllname = self.dllname
        if not dllname:
            dllname = os.path.join(os.path.dirname(self._welu.__file__),
                                   '../win32service.pyd')
        self.log_type = log_type
        self._welu.AddSourceToRegistry(self.application_name, dllname,
                                       log_type)

        self._default_type = win32evtlog.EVENTLOG_INFORMATION_TYPE
        self._type_map = {
            DEBUG:      win32evtlog.EVENTLOG_INFORMATION_TYPE,
            INFO:       win32evtlog.EVENTLOG_INFORMATION_TYPE,
            NOTICE:     win32evtlog.EVENTLOG_INFORMATION_TYPE,
            WARNING:    win32evtlog.EVENTLOG_WARNING_TYPE,
            ERROR:      win32evtlog.EVENTLOG_ERROR_TYPE,
            CRITICAL:   win32evtlog.EVENTLOG_ERROR_TYPE
        }

    def unregister_logger(self):
        """Removes the application binding from the registry.  If you call
        this, the log viewer will no longer be able to provide any
        information about the message.
        """
        self._welu.RemoveSourceFromRegistry(self.application_name,
                                            self.log_type)

    def get_event_type(self, record):
        return self._type_map.get(record.level, self._default_type)

    def get_event_category(self, record):
        """Returns the event category for the record. Override this if you want
        to specify your own categories. This version returns 0.
        """
        return 0

    def get_message_id(self, record):
        """Returns the message ID (EventID) for the record. Override this if
        you want to specify your own ID. This version returns 1.
        """
        return 1

    def emit(self, record):
        id = self.get_message_id(record)
        cat = self.get_event_category(record)
        type = self.get_event_type(record)
        self._welu.ReportEvent(self.application_name, id, cat, type,
                               [self.format(record)])


class FingersCrossedHandler(Handler):
    """This handler wraps another handler and will log everything in
    memory until a certain level (`action_level`, defaults to `ERROR`)
    is exceeded.  When that happens the fingers crossed handler will
    activate forever and log all buffered records as well as records
    yet to come into another handled which was passed to the constructor.

    Alternatively it's also possible to pass a factory function to the
    constructor instead of a handler.  That factory is then called with
    the triggering log entry and the finger crossed handler to create
    a handler which is then cached.

    The idea of this handler is to enable debugging of live systems.  For
    example it might happen that code works perfectly fine 99% of the time,
    but then some exception happens.  But the error that caused the
    exception alone might not be the interesting bit, the interesting
    information were the warnings that lead to the error.

    Here a setup that enables this for a web application::

        from logbook import FileHandler
        from logbook import FingersCrossedHandler

        def issue_logging():
            def factory(record, handler):
                return FileHandler('/var/log/app/issue-%s.log' % record.time)
            return FingersCrossedHandler(factory)

        def application(environ, start_response):
            with issue_logging():
                return the_actual_wsgi_application(environ, start_response)

    Whenever an error occours, a new file in ``/var/log/app`` is created
    with all the logging calls that lead up to the error up to the point
    where the `with` block is exited.

    Please keep in mind that the :class:`~logbook.FingersCrossedHandler`
    handler is a one-time handler.  Once triggered, it will not reset.  Because
    of that you will have to re-create it whenever you bind it.  In this case
    the handler is created when it's bound to the thread.

    Due to how the handler is implemented, the filter, bubble and level
    flags of the wrapped handler are ignored.

    .. versionchanged:: 0.3

    The default behaviour is to buffer up records and then invoke another
    handler when a severity theshold was reached with the buffer emitting.
    This now enables this logger to be properly used with the
    :class:`~logbook.MailHandler`.  You will now only get one mail for
    each buffered record.  However once the threshold was reached you would
    still get a mail for each record which is why the `reset` flag was added.

    When set to `True`, the handler will instantly reset to the untriggered
    state and start buffering again::

        handler = FingersCrossedHandler(MailHandler(...),
                                        buffer_size=10,
                                        reset=True)

    .. versionadded:: 0.3
       The `reset` flag was added.
    """

    #: the reason to be used for the batch emit.  The default is
    #: ``'escalation'``.
    #:
    #: .. versionadded:: 0.3
    batch_emit_reason = 'escalation'

    def __init__(self, handler, action_level=ERROR, buffer_size=0,
                 pull_information=True, reset=False, filter=None,
                 bubble=False):
        Handler.__init__(self, NOTSET, filter, bubble)
        self.lock = new_fine_grained_lock()
        self._level = action_level
        if isinstance(handler, Handler):
            self._handler = handler
            self._handler_factory = None
        else:
            self._handler = None
            self._handler_factory = handler
        #: the buffered records of the handler.  Once the action is triggered
        #: (:attr:`triggered`) this list will be None.  This attribute can
        #: be helpful for the handler factory function to select a proper
        #: filename (for example time of first log record)
        self.buffered_records = deque()
        #: the maximum number of entries in the buffer.  If this is exhausted
        #: the oldest entries will be discarded to make place for new ones
        self.buffer_size = buffer_size
        self._buffer_full = False
        self._pull_information = pull_information
        self._action_triggered = False
        self._reset = reset

    def close(self):
        if self._handler is not None:
            self._handler.close()

    def enqueue(self, record):
        if self._pull_information:
            record.pull_information()
        if self._action_triggered:
            self._handler.emit(record)
        else:
            self.buffered_records.append(record)
            if self._buffer_full:
                self.buffered_records.popleft()
            elif (self.buffer_size and
                    len(self.buffered_records) >= self.buffer_size):
                self._buffer_full = True
            return record.level >= self._level
        return False

    def rollover(self, record):
        if self._handler is None:
            self._handler = self._handler_factory(record, self)
        self._handler.emit_batch(iter(self.buffered_records), 'escalation')
        self.buffered_records.clear()
        self._action_triggered = not self._reset

    @property
    def triggered(self):
        """This attribute is `True` when the action was triggered.  From
        this point onwards the finger crossed handler transparently
        forwards all log records to the inner handler.  If the handler resets
        itself this will always be `False`.
        """
        return self._action_triggered

    def emit(self, record):
        self.lock.acquire()
        try:
            if self.enqueue(record):
                self.rollover(record)
        finally:
            self.lock.release()


class GroupHandler(WrapperHandler):
    """A handler that buffers all messages until it is popped again and then
    forwards all messages to another handler.  This is useful if you for
    example have an application that does computations and only a result
    mail is required.  A group handler makes sure that only one mail is sent
    and not multiple.  Some other handles might support this as well, though
    currently none of the builtins do.

    Example::

        with GroupHandler(MailHandler(...)):
            # everything here ends up in the mail

    The :class:`GroupHandler` is implemented as a :class:`WrapperHandler`
    thus forwarding all attributes of the wrapper handler.

    Notice that this handler really only emit the records when the handler
    is popped from the stack.

    .. versionadded:: 0.3
    """
    _direct_attrs = frozenset(['handler', 'pull_information',
                               'buffered_records'])

    def __init__(self, handler, pull_information=True):
        WrapperHandler.__init__(self, handler)
        self.pull_information = pull_information
        self.buffered_records = []

    def rollover(self):
        self.handler.emit_batch(self.buffered_records, 'group')
        self.buffered_records = []

    def pop_application(self):
        Handler.pop_application(self)
        self.rollover()

    def pop_thread(self):
        Handler.pop_thread(self)
        self.rollover()

    def pop_context(self):
        Handler.pop_context(self)
        self.rollover()

    def pop_greenlet(self):
        Handler.pop_greenlet(self)
        self.rollover()

    def emit(self, record):
        if self.pull_information:
            record.pull_information()
        self.buffered_records.append(record)