/usr/lib/python2.7/dist-packages/sqlalchemy/pool.py is in python-sqlalchemy 0.9.8+dfsg-0.1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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 | # sqlalchemy/pool.py
# Copyright (C) 2005-2014 the SQLAlchemy authors and contributors
# <see AUTHORS file>
#
# This module is part of SQLAlchemy and is released under
# the MIT License: http://www.opensource.org/licenses/mit-license.php
"""Connection pooling for DB-API connections.
Provides a number of connection pool implementations for a variety of
usage scenarios and thread behavior requirements imposed by the
application, DB-API or database itself.
Also provides a DB-API 2.0 connection proxying mechanism allowing
regular DB-API connect() methods to be transparently managed by a
SQLAlchemy connection pool.
"""
import time
import traceback
import weakref
from . import exc, log, event, interfaces, util
from .util import queue as sqla_queue
from .util import threading, memoized_property, \
chop_traceback
from collections import deque
proxies = {}
def manage(module, **params):
"""Return a proxy for a DB-API module that automatically
pools connections.
Given a DB-API 2.0 module and pool management parameters, returns
a proxy for the module that will automatically pool connections,
creating new connection pools for each distinct set of connection
arguments sent to the decorated module's connect() function.
:param module: a DB-API 2.0 database module
:param poolclass: the class used by the pool module to provide
pooling. Defaults to :class:`.QueuePool`.
:param \*\*params: will be passed through to *poolclass*
"""
try:
return proxies[module]
except KeyError:
return proxies.setdefault(module, _DBProxy(module, **params))
def clear_managers():
"""Remove all current DB-API 2.0 managers.
All pools and connections are disposed.
"""
for manager in proxies.values():
manager.close()
proxies.clear()
reset_rollback = util.symbol('reset_rollback')
reset_commit = util.symbol('reset_commit')
reset_none = util.symbol('reset_none')
class _ConnDialect(object):
"""partial implementation of :class:`.Dialect`
which provides DBAPI connection methods.
When a :class:`.Pool` is combined with an :class:`.Engine`,
the :class:`.Engine` replaces this with its own
:class:`.Dialect`.
"""
def do_rollback(self, dbapi_connection):
dbapi_connection.rollback()
def do_commit(self, dbapi_connection):
dbapi_connection.commit()
def do_close(self, dbapi_connection):
dbapi_connection.close()
class Pool(log.Identified):
"""Abstract base class for connection pools."""
_dialect = _ConnDialect()
def __init__(self,
creator, recycle=-1, echo=None,
use_threadlocal=False,
logging_name=None,
reset_on_return=True,
listeners=None,
events=None,
_dispatch=None,
_dialect=None):
"""
Construct a Pool.
:param creator: a callable function that returns a DB-API
connection object. The function will be called with
parameters.
:param recycle: If set to non -1, number of seconds between
connection recycling, which means upon checkout, if this
timeout is surpassed the connection will be closed and
replaced with a newly opened connection. Defaults to -1.
:param logging_name: String identifier which will be used within
the "name" field of logging records generated within the
"sqlalchemy.pool" logger. Defaults to a hexstring of the object's
id.
:param echo: If True, connections being pulled and retrieved
from the pool will be logged to the standard output, as well
as pool sizing information. Echoing can also be achieved by
enabling logging for the "sqlalchemy.pool"
namespace. Defaults to False.
:param use_threadlocal: If set to True, repeated calls to
:meth:`connect` within the same application thread will be
guaranteed to return the same connection object, if one has
already been retrieved from the pool and has not been
returned yet. Offers a slight performance advantage at the
cost of individual transactions by default. The
:meth:`.Pool.unique_connection` method is provided to return
a consistenty unique connection to bypass this behavior
when the flag is set.
.. warning:: The :paramref:`.Pool.use_threadlocal` flag
**does not affect the behavior** of :meth:`.Engine.connect`.
:meth:`.Engine.connect` makes use of the
:meth:`.Pool.unique_connection` method which **does not use thread
local context**. To produce a :class:`.Connection` which refers
to the :meth:`.Pool.connect` method, use
:meth:`.Engine.contextual_connect`.
Note that other SQLAlchemy connectivity systems such as
:meth:`.Engine.execute` as well as the orm
:class:`.Session` make use of
:meth:`.Engine.contextual_connect` internally, so these functions
are compatible with the :paramref:`.Pool.use_threadlocal` setting.
.. seealso::
:ref:`threadlocal_strategy` - contains detail on the
"threadlocal" engine strategy, which provides a more comprehensive
approach to "threadlocal" connectivity for the specific
use case of using :class:`.Engine` and :class:`.Connection` objects
directly.
:param reset_on_return: Determine steps to take on
connections as they are returned to the pool.
reset_on_return can have any of these values:
* ``"rollback"`` - call rollback() on the connection,
to release locks and transaction resources.
This is the default value. The vast majority
of use cases should leave this value set.
* ``True`` - same as 'rollback', this is here for
backwards compatibility.
* ``"commit"`` - call commit() on the connection,
to release locks and transaction resources.
A commit here may be desirable for databases that
cache query plans if a commit is emitted,
such as Microsoft SQL Server. However, this
value is more dangerous than 'rollback' because
any data changes present on the transaction
are committed unconditionally.
* ``None`` - don't do anything on the connection.
This setting should only be made on a database
that has no transaction support at all,
namely MySQL MyISAM. By not doing anything,
performance can be improved. This
setting should **never be selected** for a
database that supports transactions,
as it will lead to deadlocks and stale
state.
* ``False`` - same as None, this is here for
backwards compatibility.
.. versionchanged:: 0.7.6
:paramref:`.Pool.reset_on_return` accepts ``"rollback"``
and ``"commit"`` arguments.
:param events: a list of 2-tuples, each of the form
``(callable, target)`` which will be passed to :func:`.event.listen`
upon construction. Provided here so that event listeners
can be assigned via :func:`.create_engine` before dialect-level
listeners are applied.
:param listeners: Deprecated. A list of
:class:`~sqlalchemy.interfaces.PoolListener`-like objects or
dictionaries of callables that receive events when DB-API
connections are created, checked out and checked in to the
pool. This has been superseded by
:func:`~sqlalchemy.event.listen`.
"""
if logging_name:
self.logging_name = self._orig_logging_name = logging_name
else:
self._orig_logging_name = None
log.instance_logger(self, echoflag=echo)
self._threadconns = threading.local()
self._creator = creator
self._recycle = recycle
self._invalidate_time = 0
self._use_threadlocal = use_threadlocal
if reset_on_return in ('rollback', True, reset_rollback):
self._reset_on_return = reset_rollback
elif reset_on_return in (None, False, reset_none):
self._reset_on_return = reset_none
elif reset_on_return in ('commit', reset_commit):
self._reset_on_return = reset_commit
else:
raise exc.ArgumentError(
"Invalid value for 'reset_on_return': %r"
% reset_on_return)
self.echo = echo
if _dispatch:
self.dispatch._update(_dispatch, only_propagate=False)
if _dialect:
self._dialect = _dialect
if events:
for fn, target in events:
event.listen(self, target, fn)
if listeners:
util.warn_deprecated(
"The 'listeners' argument to Pool (and "
"create_engine()) is deprecated. Use event.listen().")
for l in listeners:
self.add_listener(l)
def _close_connection(self, connection):
self.logger.debug("Closing connection %r", connection)
try:
self._dialect.do_close(connection)
except (SystemExit, KeyboardInterrupt):
raise
except:
self.logger.error("Exception closing connection %r",
connection, exc_info=True)
@util.deprecated(
2.7, "Pool.add_listener is deprecated. Use event.listen()")
def add_listener(self, listener):
"""Add a :class:`.PoolListener`-like object to this pool.
``listener`` may be an object that implements some or all of
PoolListener, or a dictionary of callables containing implementations
of some or all of the named methods in PoolListener.
"""
interfaces.PoolListener._adapt_listener(self, listener)
def unique_connection(self):
"""Produce a DBAPI connection that is not referenced by any
thread-local context.
This method is equivalent to :meth:`.Pool.connect` when the
:paramref:`.Pool.use_threadlocal` flag is not set to True.
When :paramref:`.Pool.use_threadlocal` is True, the
:meth:`.Pool.unique_connection` method provides a means of bypassing
the threadlocal context.
"""
return _ConnectionFairy._checkout(self)
def _create_connection(self):
"""Called by subclasses to create a new ConnectionRecord."""
return _ConnectionRecord(self)
def _invalidate(self, connection, exception=None):
"""Mark all connections established within the generation
of the given connection as invalidated.
If this pool's last invalidate time is before when the given
connection was created, update the timestamp til now. Otherwise,
no action is performed.
Connections with a start time prior to this pool's invalidation
time will be recycled upon next checkout.
"""
rec = getattr(connection, "_connection_record", None)
if not rec or self._invalidate_time < rec.starttime:
self._invalidate_time = time.time()
if getattr(connection, 'is_valid', False):
connection.invalidate(exception)
def recreate(self):
"""Return a new :class:`.Pool`, of the same class as this one
and configured with identical creation arguments.
This method is used in conjunction with :meth:`dispose`
to close out an entire :class:`.Pool` and create a new one in
its place.
"""
raise NotImplementedError()
def dispose(self):
"""Dispose of this pool.
This method leaves the possibility of checked-out connections
remaining open, as it only affects connections that are
idle in the pool.
See also the :meth:`Pool.recreate` method.
"""
raise NotImplementedError()
def connect(self):
"""Return a DBAPI connection from the pool.
The connection is instrumented such that when its
``close()`` method is called, the connection will be returned to
the pool.
"""
if not self._use_threadlocal:
return _ConnectionFairy._checkout(self)
try:
rec = self._threadconns.current()
except AttributeError:
pass
else:
if rec is not None:
return rec._checkout_existing()
return _ConnectionFairy._checkout(self, self._threadconns)
def _return_conn(self, record):
"""Given a _ConnectionRecord, return it to the :class:`.Pool`.
This method is called when an instrumented DBAPI connection
has its ``close()`` method called.
"""
if self._use_threadlocal:
try:
del self._threadconns.current
except AttributeError:
pass
self._do_return_conn(record)
def _do_get(self):
"""Implementation for :meth:`get`, supplied by subclasses."""
raise NotImplementedError()
def _do_return_conn(self, conn):
"""Implementation for :meth:`return_conn`, supplied by subclasses."""
raise NotImplementedError()
def status(self):
raise NotImplementedError()
class _ConnectionRecord(object):
"""Internal object which maintains an individual DBAPI connection
referenced by a :class:`.Pool`.
The :class:`._ConnectionRecord` object always exists for any particular
DBAPI connection whether or not that DBAPI connection has been
"checked out". This is in contrast to the :class:`._ConnectionFairy`
which is only a public facade to the DBAPI connection while it is checked
out.
A :class:`._ConnectionRecord` may exist for a span longer than that
of a single DBAPI connection. For example, if the
:meth:`._ConnectionRecord.invalidate`
method is called, the DBAPI connection associated with this
:class:`._ConnectionRecord`
will be discarded, but the :class:`._ConnectionRecord` may be used again,
in which case a new DBAPI connection is produced when the :class:`.Pool`
next uses this record.
The :class:`._ConnectionRecord` is delivered along with connection
pool events, including :meth:`.PoolEvents.connect` and
:meth:`.PoolEvents.checkout`, however :class:`._ConnectionRecord` still
remains an internal object whose API and internals may change.
.. seealso::
:class:`._ConnectionFairy`
"""
def __init__(self, pool):
self.__pool = pool
self.connection = self.__connect()
self.finalize_callback = deque()
pool.dispatch.first_connect.\
for_modify(pool.dispatch).\
exec_once(self.connection, self)
pool.dispatch.connect(self.connection, self)
connection = None
"""A reference to the actual DBAPI connection being tracked.
May be ``None`` if this :class:`._ConnectionRecord` has been marked
as invalidated; a new DBAPI connection may replace it if the owning
pool calls upon this :class:`._ConnectionRecord` to reconnect.
"""
@util.memoized_property
def info(self):
"""The ``.info`` dictionary associated with the DBAPI connection.
This dictionary is shared among the :attr:`._ConnectionFairy.info`
and :attr:`.Connection.info` accessors.
"""
return {}
@classmethod
def checkout(cls, pool):
rec = pool._do_get()
try:
dbapi_connection = rec.get_connection()
except:
rec.checkin()
raise
echo = pool._should_log_debug()
fairy = _ConnectionFairy(dbapi_connection, rec, echo)
rec.fairy_ref = weakref.ref(
fairy,
lambda ref: _finalize_fairy and
_finalize_fairy(
dbapi_connection,
rec, pool, ref, echo)
)
_refs.add(rec)
if echo:
pool.logger.debug("Connection %r checked out from pool",
dbapi_connection)
return fairy
def checkin(self):
self.fairy_ref = None
connection = self.connection
pool = self.__pool
while self.finalize_callback:
finalizer = self.finalize_callback.pop()
finalizer(connection)
if pool.dispatch.checkin:
pool.dispatch.checkin(connection, self)
pool._return_conn(self)
def close(self):
if self.connection is not None:
self.__close()
def invalidate(self, e=None):
"""Invalidate the DBAPI connection held by this :class:`._ConnectionRecord`.
This method is called for all connection invalidations, including
when the :meth:`._ConnectionFairy.invalidate` or
:meth:`.Connection.invalidate` methods are called, as well as when any
so-called "automatic invalidation" condition occurs.
.. seealso::
:ref:`pool_connection_invalidation`
"""
# already invalidated
if self.connection is None:
return
self.__pool.dispatch.invalidate(self.connection, self, e)
if e is not None:
self.__pool.logger.info(
"Invalidate connection %r (reason: %s:%s)",
self.connection, e.__class__.__name__, e)
else:
self.__pool.logger.info(
"Invalidate connection %r", self.connection)
self.__close()
self.connection = None
def get_connection(self):
recycle = False
if self.connection is None:
self.connection = self.__connect()
self.info.clear()
if self.__pool.dispatch.connect:
self.__pool.dispatch.connect(self.connection, self)
elif self.__pool._recycle > -1 and \
time.time() - self.starttime > self.__pool._recycle:
self.__pool.logger.info(
"Connection %r exceeded timeout; recycling",
self.connection)
recycle = True
elif self.__pool._invalidate_time > self.starttime:
self.__pool.logger.info(
"Connection %r invalidated due to pool invalidation; " +
"recycling",
self.connection
)
recycle = True
if recycle:
self.__close()
self.connection = self.__connect()
self.info.clear()
if self.__pool.dispatch.connect:
self.__pool.dispatch.connect(self.connection, self)
return self.connection
def __close(self):
self.__pool._close_connection(self.connection)
def __connect(self):
try:
self.starttime = time.time()
connection = self.__pool._creator()
self.__pool.logger.debug("Created new connection %r", connection)
return connection
except Exception as e:
self.__pool.logger.debug("Error on connect(): %s", e)
raise
def _finalize_fairy(connection, connection_record,
pool, ref, echo, fairy=None):
"""Cleanup for a :class:`._ConnectionFairy` whether or not it's already
been garbage collected.
"""
_refs.discard(connection_record)
if ref is not None and \
connection_record.fairy_ref is not ref:
return
if connection is not None:
if connection_record and echo:
pool.logger.debug("Connection %r being returned to pool",
connection)
try:
fairy = fairy or _ConnectionFairy(
connection, connection_record, echo)
assert fairy.connection is connection
fairy._reset(pool)
# Immediately close detached instances
if not connection_record:
pool._close_connection(connection)
except Exception as e:
pool.logger.error(
"Exception during reset or similar", exc_info=True)
if connection_record:
connection_record.invalidate(e=e)
if isinstance(e, (SystemExit, KeyboardInterrupt)):
raise
if connection_record:
connection_record.checkin()
_refs = set()
class _ConnectionFairy(object):
"""Proxies a DBAPI connection and provides return-on-dereference
support.
This is an internal object used by the :class:`.Pool` implementation
to provide context management to a DBAPI connection delivered by
that :class:`.Pool`.
The name "fairy" is inspired by the fact that the
:class:`._ConnectionFairy` object's lifespan is transitory, as it lasts
only for the length of a specific DBAPI connection being checked out from
the pool, and additionally that as a transparent proxy, it is mostly
invisible.
.. seealso::
:class:`._ConnectionRecord`
"""
def __init__(self, dbapi_connection, connection_record, echo):
self.connection = dbapi_connection
self._connection_record = connection_record
self._echo = echo
connection = None
"""A reference to the actual DBAPI connection being tracked."""
_connection_record = None
"""A reference to the :class:`._ConnectionRecord` object associated
with the DBAPI connection.
This is currently an internal accessor which is subject to change.
"""
_reset_agent = None
"""Refer to an object with a ``.commit()`` and ``.rollback()`` method;
if non-None, the "reset-on-return" feature will call upon this object
rather than directly against the dialect-level do_rollback() and
do_commit() methods.
In practice, a :class:`.Connection` assigns a :class:`.Transaction` object
to this variable when one is in scope so that the :class:`.Transaction`
takes the job of committing or rolling back on return if
:meth:`.Connection.close` is called while the :class:`.Transaction`
still exists.
This is essentially an "event handler" of sorts but is simplified as an
instance variable both for performance/simplicity as well as that there
can only be one "reset agent" at a time.
"""
@classmethod
def _checkout(cls, pool, threadconns=None, fairy=None):
if not fairy:
fairy = _ConnectionRecord.checkout(pool)
fairy._pool = pool
fairy._counter = 0
if threadconns is not None:
threadconns.current = weakref.ref(fairy)
if fairy.connection is None:
raise exc.InvalidRequestError("This connection is closed")
fairy._counter += 1
if not pool.dispatch.checkout or fairy._counter != 1:
return fairy
# Pool listeners can trigger a reconnection on checkout
attempts = 2
while attempts > 0:
try:
pool.dispatch.checkout(fairy.connection,
fairy._connection_record,
fairy)
return fairy
except exc.DisconnectionError as e:
pool.logger.info(
"Disconnection detected on checkout: %s", e)
fairy._connection_record.invalidate(e)
fairy.connection = fairy._connection_record.get_connection()
attempts -= 1
pool.logger.info("Reconnection attempts exhausted on checkout")
fairy.invalidate()
raise exc.InvalidRequestError("This connection is closed")
def _checkout_existing(self):
return _ConnectionFairy._checkout(self._pool, fairy=self)
def _checkin(self):
_finalize_fairy(self.connection, self._connection_record,
self._pool, None, self._echo, fairy=self)
self.connection = None
self._connection_record = None
_close = _checkin
def _reset(self, pool):
if pool.dispatch.reset:
pool.dispatch.reset(self, self._connection_record)
if pool._reset_on_return is reset_rollback:
if self._echo:
pool.logger.debug("Connection %s rollback-on-return%s",
self.connection,
", via agent"
if self._reset_agent else "")
if self._reset_agent:
self._reset_agent.rollback()
else:
pool._dialect.do_rollback(self)
elif pool._reset_on_return is reset_commit:
if self._echo:
pool.logger.debug("Connection %s commit-on-return%s",
self.connection,
", via agent"
if self._reset_agent else "")
if self._reset_agent:
self._reset_agent.commit()
else:
pool._dialect.do_commit(self)
@property
def _logger(self):
return self._pool.logger
@property
def is_valid(self):
"""Return True if this :class:`._ConnectionFairy` still refers
to an active DBAPI connection."""
return self.connection is not None
@util.memoized_property
def info(self):
"""Info dictionary associated with the underlying DBAPI connection
referred to by this :class:`.ConnectionFairy`, allowing user-defined
data to be associated with the connection.
The data here will follow along with the DBAPI connection including
after it is returned to the connection pool and used again
in subsequent instances of :class:`._ConnectionFairy`. It is shared
with the :attr:`._ConnectionRecord.info` and :attr:`.Connection.info`
accessors.
"""
return self._connection_record.info
def invalidate(self, e=None):
"""Mark this connection as invalidated.
This method can be called directly, and is also called as a result
of the :meth:`.Connection.invalidate` method. When invoked,
the DBAPI connection is immediately closed and discarded from
further use by the pool. The invalidation mechanism proceeds
via the :meth:`._ConnectionRecord.invalidate` internal method.
.. seealso::
:ref:`pool_connection_invalidation`
"""
if self.connection is None:
util.warn("Can't invalidate an already-closed connection.")
return
if self._connection_record:
self._connection_record.invalidate(e=e)
self.connection = None
self._checkin()
def cursor(self, *args, **kwargs):
"""Return a new DBAPI cursor for the underlying connection.
This method is a proxy for the ``connection.cursor()`` DBAPI
method.
"""
return self.connection.cursor(*args, **kwargs)
def __getattr__(self, key):
return getattr(self.connection, key)
def detach(self):
"""Separate this connection from its Pool.
This means that the connection will no longer be returned to the
pool when closed, and will instead be literally closed. The
containing ConnectionRecord is separated from the DB-API connection,
and will create a new connection when next used.
Note that any overall connection limiting constraints imposed by a
Pool implementation may be violated after a detach, as the detached
connection is removed from the pool's knowledge and control.
"""
if self._connection_record is not None:
_refs.remove(self._connection_record)
self._connection_record.fairy_ref = None
self._connection_record.connection = None
# TODO: should this be _return_conn?
self._pool._do_return_conn(self._connection_record)
self.info = self.info.copy()
self._connection_record = None
def close(self):
self._counter -= 1
if self._counter == 0:
self._checkin()
class SingletonThreadPool(Pool):
"""A Pool that maintains one connection per thread.
Maintains one connection per each thread, never moving a connection to a
thread other than the one which it was created in.
Options are the same as those of :class:`.Pool`, as well as:
:param pool_size: The number of threads in which to maintain connections
at once. Defaults to five.
:class:`.SingletonThreadPool` is used by the SQLite dialect
automatically when a memory-based database is used.
See :ref:`sqlite_toplevel`.
"""
def __init__(self, creator, pool_size=5, **kw):
kw['use_threadlocal'] = True
Pool.__init__(self, creator, **kw)
self._conn = threading.local()
self._all_conns = set()
self.size = pool_size
def recreate(self):
self.logger.info("Pool recreating")
return self.__class__(self._creator,
pool_size=self.size,
recycle=self._recycle,
echo=self.echo,
logging_name=self._orig_logging_name,
use_threadlocal=self._use_threadlocal,
reset_on_return=self._reset_on_return,
_dispatch=self.dispatch,
_dialect=self._dialect)
def dispose(self):
"""Dispose of this pool."""
for conn in self._all_conns:
try:
conn.close()
except (SystemExit, KeyboardInterrupt):
raise
except:
# pysqlite won't even let you close a conn from a thread
# that didn't create it
pass
self._all_conns.clear()
def _cleanup(self):
while len(self._all_conns) >= self.size:
c = self._all_conns.pop()
c.close()
def status(self):
return "SingletonThreadPool id:%d size: %d" % \
(id(self), len(self._all_conns))
def _do_return_conn(self, conn):
pass
def _do_get(self):
try:
c = self._conn.current()
if c:
return c
except AttributeError:
pass
c = self._create_connection()
self._conn.current = weakref.ref(c)
if len(self._all_conns) >= self.size:
self._cleanup()
self._all_conns.add(c)
return c
class QueuePool(Pool):
"""A :class:`.Pool` that imposes a limit on the number of open connections.
:class:`.QueuePool` is the default pooling implementation used for
all :class:`.Engine` objects, unless the SQLite dialect is in use.
"""
def __init__(self, creator, pool_size=5, max_overflow=10, timeout=30,
**kw):
"""
Construct a QueuePool.
:param creator: a callable function that returns a DB-API
connection object, same as that of :paramref:`.Pool.creator`.
:param pool_size: The size of the pool to be maintained,
defaults to 5. This is the largest number of connections that
will be kept persistently in the pool. Note that the pool
begins with no connections; once this number of connections
is requested, that number of connections will remain.
``pool_size`` can be set to 0 to indicate no size limit; to
disable pooling, use a :class:`~sqlalchemy.pool.NullPool`
instead.
:param max_overflow: The maximum overflow size of the
pool. When the number of checked-out connections reaches the
size set in pool_size, additional connections will be
returned up to this limit. When those additional connections
are returned to the pool, they are disconnected and
discarded. It follows then that the total number of
simultaneous connections the pool will allow is pool_size +
`max_overflow`, and the total number of "sleeping"
connections the pool will allow is pool_size. `max_overflow`
can be set to -1 to indicate no overflow limit; no limit
will be placed on the total number of concurrent
connections. Defaults to 10.
:param timeout: The number of seconds to wait before giving up
on returning a connection. Defaults to 30.
:param \**kw: Other keyword arguments including
:paramref:`.Pool.recycle`, :paramref:`.Pool.echo`,
:paramref:`.Pool.reset_on_return` and others are passed to the
:class:`.Pool` constructor.
"""
Pool.__init__(self, creator, **kw)
self._pool = sqla_queue.Queue(pool_size)
self._overflow = 0 - pool_size
self._max_overflow = max_overflow
self._timeout = timeout
self._overflow_lock = threading.Lock()
def _do_return_conn(self, conn):
try:
self._pool.put(conn, False)
except sqla_queue.Full:
try:
conn.close()
finally:
self._dec_overflow()
def _do_get(self):
use_overflow = self._max_overflow > -1
try:
wait = use_overflow and self._overflow >= self._max_overflow
return self._pool.get(wait, self._timeout)
except sqla_queue.Empty:
if use_overflow and self._overflow >= self._max_overflow:
if not wait:
return self._do_get()
else:
raise exc.TimeoutError(
"QueuePool limit of size %d overflow %d reached, "
"connection timed out, timeout %d" %
(self.size(), self.overflow(), self._timeout))
if self._inc_overflow():
try:
return self._create_connection()
except:
self._dec_overflow()
raise
else:
return self._do_get()
def _inc_overflow(self):
if self._max_overflow == -1:
self._overflow += 1
return True
with self._overflow_lock:
if self._overflow < self._max_overflow:
self._overflow += 1
return True
else:
return False
def _dec_overflow(self):
if self._max_overflow == -1:
self._overflow -= 1
return True
with self._overflow_lock:
self._overflow -= 1
return True
def recreate(self):
self.logger.info("Pool recreating")
return self.__class__(self._creator, pool_size=self._pool.maxsize,
max_overflow=self._max_overflow,
timeout=self._timeout,
recycle=self._recycle, echo=self.echo,
logging_name=self._orig_logging_name,
use_threadlocal=self._use_threadlocal,
reset_on_return=self._reset_on_return,
_dispatch=self.dispatch,
_dialect=self._dialect)
def dispose(self):
while True:
try:
conn = self._pool.get(False)
conn.close()
except sqla_queue.Empty:
break
self._overflow = 0 - self.size()
self.logger.info("Pool disposed. %s", self.status())
def status(self):
return "Pool size: %d Connections in pool: %d "\
"Current Overflow: %d Current Checked out "\
"connections: %d" % (self.size(),
self.checkedin(),
self.overflow(),
self.checkedout())
def size(self):
return self._pool.maxsize
def checkedin(self):
return self._pool.qsize()
def overflow(self):
return self._overflow
def checkedout(self):
return self._pool.maxsize - self._pool.qsize() + self._overflow
class NullPool(Pool):
"""A Pool which does not pool connections.
Instead it literally opens and closes the underlying DB-API connection
per each connection open/close.
Reconnect-related functions such as ``recycle`` and connection
invalidation are not supported by this Pool implementation, since
no connections are held persistently.
.. versionchanged:: 0.7
:class:`.NullPool` is used by the SQlite dialect automatically
when a file-based database is used. See :ref:`sqlite_toplevel`.
"""
def status(self):
return "NullPool"
def _do_return_conn(self, conn):
conn.close()
def _do_get(self):
return self._create_connection()
def recreate(self):
self.logger.info("Pool recreating")
return self.__class__(self._creator,
recycle=self._recycle,
echo=self.echo,
logging_name=self._orig_logging_name,
use_threadlocal=self._use_threadlocal,
reset_on_return=self._reset_on_return,
_dispatch=self.dispatch,
_dialect=self._dialect)
def dispose(self):
pass
class StaticPool(Pool):
"""A Pool of exactly one connection, used for all requests.
Reconnect-related functions such as ``recycle`` and connection
invalidation (which is also used to support auto-reconnect) are not
currently supported by this Pool implementation but may be implemented
in a future release.
"""
@memoized_property
def _conn(self):
return self._creator()
@memoized_property
def connection(self):
return _ConnectionRecord(self)
def status(self):
return "StaticPool"
def dispose(self):
if '_conn' in self.__dict__:
self._conn.close()
self._conn = None
def recreate(self):
self.logger.info("Pool recreating")
return self.__class__(creator=self._creator,
recycle=self._recycle,
use_threadlocal=self._use_threadlocal,
reset_on_return=self._reset_on_return,
echo=self.echo,
logging_name=self._orig_logging_name,
_dispatch=self.dispatch,
_dialect=self._dialect)
def _create_connection(self):
return self._conn
def _do_return_conn(self, conn):
pass
def _do_get(self):
return self.connection
class AssertionPool(Pool):
"""A :class:`.Pool` that allows at most one checked out connection at
any given time.
This will raise an exception if more than one connection is checked out
at a time. Useful for debugging code that is using more connections
than desired.
.. versionchanged:: 0.7
:class:`.AssertionPool` also logs a traceback of where
the original connection was checked out, and reports
this in the assertion error raised.
"""
def __init__(self, *args, **kw):
self._conn = None
self._checked_out = False
self._store_traceback = kw.pop('store_traceback', True)
self._checkout_traceback = None
Pool.__init__(self, *args, **kw)
def status(self):
return "AssertionPool"
def _do_return_conn(self, conn):
if not self._checked_out:
raise AssertionError("connection is not checked out")
self._checked_out = False
assert conn is self._conn
def dispose(self):
self._checked_out = False
if self._conn:
self._conn.close()
def recreate(self):
self.logger.info("Pool recreating")
return self.__class__(self._creator, echo=self.echo,
logging_name=self._orig_logging_name,
_dispatch=self.dispatch,
_dialect=self._dialect)
def _do_get(self):
if self._checked_out:
if self._checkout_traceback:
suffix = ' at:\n%s' % ''.join(
chop_traceback(self._checkout_traceback))
else:
suffix = ''
raise AssertionError("connection is already checked out" + suffix)
if not self._conn:
self._conn = self._create_connection()
self._checked_out = True
if self._store_traceback:
self._checkout_traceback = traceback.format_stack()
return self._conn
class _DBProxy(object):
"""Layers connection pooling behavior on top of a standard DB-API module.
Proxies a DB-API 2.0 connect() call to a connection pool keyed to the
specific connect parameters. Other functions and attributes are delegated
to the underlying DB-API module.
"""
def __init__(self, module, poolclass=QueuePool, **kw):
"""Initializes a new proxy.
module
a DB-API 2.0 module
poolclass
a Pool class, defaulting to QueuePool
Other parameters are sent to the Pool object's constructor.
"""
self.module = module
self.kw = kw
self.poolclass = poolclass
self.pools = {}
self._create_pool_mutex = threading.Lock()
def close(self):
for key in list(self.pools):
del self.pools[key]
def __del__(self):
self.close()
def __getattr__(self, key):
return getattr(self.module, key)
def get_pool(self, *args, **kw):
key = self._serialize(*args, **kw)
try:
return self.pools[key]
except KeyError:
self._create_pool_mutex.acquire()
try:
if key not in self.pools:
kw.pop('sa_pool_key', None)
pool = self.poolclass(
lambda: self.module.connect(*args, **kw), **self.kw)
self.pools[key] = pool
return pool
else:
return self.pools[key]
finally:
self._create_pool_mutex.release()
def connect(self, *args, **kw):
"""Activate a connection to the database.
Connect to the database using this DBProxy's module and the given
connect arguments. If the arguments match an existing pool, the
connection will be returned from the pool's current thread-local
connection instance, or if there is no thread-local connection
instance it will be checked out from the set of pooled connections.
If the pool has no available connections and allows new connections
to be created, a new database connection will be made.
"""
return self.get_pool(*args, **kw).connect()
def dispose(self, *args, **kw):
"""Dispose the pool referenced by the given connect arguments."""
key = self._serialize(*args, **kw)
try:
del self.pools[key]
except KeyError:
pass
def _serialize(self, *args, **kw):
if "sa_pool_key" in kw:
return kw['sa_pool_key']
return tuple(
list(args) +
[(k, kw[k]) for k in sorted(kw)]
)
|