From: Mike Bayer Date: Sat, 22 Mar 2014 22:45:39 +0000 (-0400) Subject: - A major improvement made to the mechanics by which the :class:`.Engine` X-Git-Tag: rel_0_9_4~42 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=eed9cfc3ae027f21a1f46a6e07fcef0724741eb2;p=thirdparty%2Fsqlalchemy%2Fsqlalchemy.git - A major improvement made to the mechanics by which the :class:`.Engine` recycles the connection pool when a "disconnect" condition is detected; instead of discarding the pool and explicitly closing out connections, the pool is retained and a "generational" timestamp is updated to reflect the current time, thereby causing all existing connections to be recycled when they are next checked out. This greatly simplifies the recycle process, removes the need for "waking up" connect attempts waiting on the old pool and eliminates the race condition that many immediately-discarded "pool" objects could be created during the recycle operation. fixes #2985 --- diff --git a/doc/build/changelog/changelog_09.rst b/doc/build/changelog/changelog_09.rst index 2e4e5f0983..c4fa76e493 100644 --- a/doc/build/changelog/changelog_09.rst +++ b/doc/build/changelog/changelog_09.rst @@ -14,6 +14,21 @@ .. changelog:: :version: 0.9.4 + .. change:: + :tags: bug, engine + :tickets: 2985 + + A major improvement made to the mechanics by which the :class:`.Engine` + recycles the connection pool when a "disconnect" condition is detected; + instead of discarding the pool and explicitly closing out connections, + the pool is retained and a "generational" timestamp is updated to + reflect the current time, thereby causing all existing connections + to be recycled when they are next checked out. This greatly simplifies + the recycle process, removes the need for "waking up" connect attempts + waiting on the old pool and eliminates the race condition that many + immediately-discarded "pool" objects could be created during the + recycle operation. + .. change:: :tags: bug, oracle :tickets: 2987 diff --git a/lib/sqlalchemy/engine/base.py b/lib/sqlalchemy/engine/base.py index d3024640bb..2cad2a0949 100644 --- a/lib/sqlalchemy/engine/base.py +++ b/lib/sqlalchemy/engine/base.py @@ -1091,9 +1091,7 @@ class Connection(Connectable): del self._is_disconnect dbapi_conn_wrapper = self.connection self.invalidate(e) - if not hasattr(dbapi_conn_wrapper, '_pool') or \ - dbapi_conn_wrapper._pool is self.engine.pool: - self.engine.dispose() + self.engine.pool._invalidate(dbapi_conn_wrapper) if self.should_close_with_result: self.close() @@ -1503,7 +1501,7 @@ class Engine(Connectable, log.Identified): the engine are not affected. """ - self.pool = self.pool._replace() + self.pool.dispose() def _execute_default(self, default): with self.contextual_connect() as conn: diff --git a/lib/sqlalchemy/orm/strategies.py b/lib/sqlalchemy/orm/strategies.py index 473b665c83..4a07e78569 100644 --- a/lib/sqlalchemy/orm/strategies.py +++ b/lib/sqlalchemy/orm/strategies.py @@ -528,7 +528,6 @@ class LazyLoader(AbstractRelationshipLoader): def _emit_lazyload(self, strategy_options, session, state, ident_key, passive): q = session.query(self.mapper)._adapt_all_clauses() - if self.parent_property.secondary is not None: q = q.select_from(self.mapper, self.parent_property.secondary) diff --git a/lib/sqlalchemy/pool.py b/lib/sqlalchemy/pool.py index 59c1e614a2..7fc4fc6591 100644 --- a/lib/sqlalchemy/pool.py +++ b/lib/sqlalchemy/pool.py @@ -210,6 +210,7 @@ class Pool(log.Identified): 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 @@ -276,6 +277,22 @@ class Pool(log.Identified): return _ConnectionRecord(self) + def _invalidate(self, connection): + """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() + + def recreate(self): """Return a new :class:`.Pool`, of the same class as this one and configured with identical creation arguments. @@ -301,17 +318,6 @@ class Pool(log.Identified): raise NotImplementedError() - def _replace(self): - """Dispose + recreate this pool. - - Subclasses may employ special logic to - move threads waiting on this pool to the - new one. - - """ - self.dispose() - return self.recreate() - def connect(self): """Return a DBAPI connection from the pool. @@ -483,6 +489,7 @@ class _ConnectionRecord(object): self.connection = None def get_connection(self): + recycle = False if self.connection is None: self.connection = self.__connect() self.info.clear() @@ -493,6 +500,15 @@ class _ConnectionRecord(object): 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() @@ -911,8 +927,6 @@ class QueuePool(Pool): try: wait = use_overflow and self._overflow >= self._max_overflow return self._pool.get(wait, self._timeout) - except sqla_queue.SAAbort as aborted: - return aborted.context._do_get() except sqla_queue.Empty: if use_overflow and self._overflow >= self._max_overflow: if not wait: @@ -974,12 +988,6 @@ class QueuePool(Pool): self._overflow = 0 - self.size() self.logger.info("Pool disposed. %s", self.status()) - def _replace(self): - self.dispose() - np = self.recreate() - self._pool.abort(np) - return np - def status(self): return "Pool size: %d Connections in pool: %d "\ "Current Overflow: %d Current Checked out "\ diff --git a/lib/sqlalchemy/util/queue.py b/lib/sqlalchemy/util/queue.py index 82ff55a5d3..c98aa7fdab 100644 --- a/lib/sqlalchemy/util/queue.py +++ b/lib/sqlalchemy/util/queue.py @@ -15,11 +15,6 @@ rare cases be invoked within the ``get()`` method of the Queue itself, producing a ``put()`` inside the ``get()`` and therefore a reentrant condition. -An additional change includes a special "abort" method which can be used -to immediately raise a special exception for threads that are blocking -on get(). This is to accommodate a rare race condition that can occur -within QueuePool. - """ from collections import deque @@ -27,7 +22,7 @@ from time import time as _time from .compat import threading -__all__ = ['Empty', 'Full', 'Queue', 'SAAbort'] +__all__ = ['Empty', 'Full', 'Queue'] class Empty(Exception): @@ -42,12 +37,6 @@ class Full(Exception): pass -class SAAbort(Exception): - "Special SQLA exception to abort waiting" - def __init__(self, context): - self.context = context - - class Queue: def __init__(self, maxsize=0): """Initialize a queue object with a given maximum size. @@ -68,8 +57,6 @@ class Queue: # a thread waiting to put is notified then. self.not_full = threading.Condition(self.mutex) - # when this is set, SAAbort is raised within get(). - self._sqla_abort_context = False def qsize(self): """Return the approximate size of the queue (not reliable!).""" @@ -158,13 +145,7 @@ class Queue: raise Empty elif timeout is None: while self._empty(): - # wait for only half a second, then - # loop around, so that we can see a change in - # _sqla_abort_context in case we missed the notify_all() - # called by abort() - self.not_empty.wait(.5) - if self._sqla_abort_context: - raise SAAbort(self._sqla_abort_context) + self.not_empty.wait() else: if timeout < 0: raise ValueError("'timeout' must be a positive number") @@ -174,30 +155,12 @@ class Queue: if remaining <= 0.0: raise Empty self.not_empty.wait(remaining) - if self._sqla_abort_context: - raise SAAbort(self._sqla_abort_context) item = self._get() self.not_full.notify() return item finally: self.not_empty.release() - def abort(self, context): - """Issue an 'abort', will force any thread waiting on get() - to stop waiting and raise SAAbort. - - """ - self._sqla_abort_context = context - if not self.not_full.acquire(False): - return - try: - # note that this is now optional - # as the waiters in get() both loop around - # to check the _sqla_abort_context flag periodically - self.not_empty.notify_all() - finally: - self.not_full.release() - def get_nowait(self): """Remove and return an item from the queue without blocking. diff --git a/test/engine/test_pool.py b/test/engine/test_pool.py index fc6f3dceaa..bbab0a7c3d 100644 --- a/test/engine/test_pool.py +++ b/test/engine/test_pool.py @@ -7,7 +7,7 @@ from sqlalchemy.testing.util import gc_collect, lazy_gc from sqlalchemy.testing import eq_, assert_raises, is_not_ from sqlalchemy.testing.engines import testing_engine from sqlalchemy.testing import fixtures - +import random from sqlalchemy.testing.mock import Mock, call join_timeout = 10 @@ -1069,7 +1069,8 @@ class QueuePoolTest(PoolTestBase): # inside the queue, before we invalidate the other # two conns time.sleep(.2) - p2 = p._replace() + p._invalidate(c2) + c2.invalidate() for t in threads: t.join(join_timeout) @@ -1079,19 +1080,18 @@ class QueuePoolTest(PoolTestBase): @testing.requires.threading_with_mock def test_notify_waiters(self): dbapi = MockDBAPI() + canary = [] - def creator1(): + def creator(): canary.append(1) return dbapi.connect() - def creator2(): - canary.append(2) - return dbapi.connect() - p1 = pool.QueuePool(creator=creator1, + p1 = pool.QueuePool(creator=creator, pool_size=1, timeout=None, max_overflow=0) - p2 = pool.NullPool(creator=creator2) + #p2 = pool.NullPool(creator=creator2) def waiter(p): conn = p.connect() + canary.append(2) time.sleep(.5) conn.close() @@ -1104,12 +1104,14 @@ class QueuePoolTest(PoolTestBase): threads.append(t) time.sleep(.5) eq_(canary, [1]) - p1._pool.abort(p2) + + c1.invalidate() + p1._invalidate(c1) for t in threads: t.join(join_timeout) - eq_(canary, [1, 2, 2, 2, 2, 2]) + eq_(canary, [1, 1, 2, 2, 2, 2, 2]) def test_dispose_closes_pooled(self): dbapi = MockDBAPI() @@ -1251,6 +1253,21 @@ class QueuePoolTest(PoolTestBase): c3 = p.connect() assert id(c3.connection) != c_id + def test_recycle_on_invalidate(self): + p = self._queuepool_fixture(pool_size=1, + max_overflow=0) + c1 = p.connect() + c_id = id(c1.connection) + c1.close() + c2 = p.connect() + assert id(c2.connection) == c_id + + p._invalidate(c2) + c2.close() + time.sleep(.5) + c3 = p.connect() + assert id(c3.connection) != c_id + def _assert_cleanup_on_pooled_reconnect(self, dbapi, p): # p is QueuePool with size=1, max_overflow=2, # and one connection in the pool that will need to @@ -1290,6 +1307,72 @@ class QueuePoolTest(PoolTestBase): time.sleep(1) self._assert_cleanup_on_pooled_reconnect(dbapi, p) + def test_recycle_pool_no_race(self): + def slow_close(): + slow_closing_connection._slow_close() + time.sleep(.5) + + slow_closing_connection = Mock() + slow_closing_connection.connect.return_value.close = slow_close + + class Error(Exception): + pass + + dialect = Mock() + dialect.is_disconnect = lambda *arg, **kw: True + dialect.dbapi.Error = Error + + pools = [] + class TrackQueuePool(pool.QueuePool): + def __init__(self, *arg, **kw): + pools.append(self) + super(TrackQueuePool, self).__init__(*arg, **kw) + + def creator(): + return slow_closing_connection.connect() + p1 = TrackQueuePool(creator=creator, pool_size=20) + + from sqlalchemy import create_engine + eng = create_engine("postgresql://", pool=p1, _initialize=False) + eng.dialect = dialect + + # 15 total connections + conns = [eng.connect() for i in range(15)] + + # return 8 back to the pool + for conn in conns[3:10]: + conn.close() + + def attempt(conn): + time.sleep(random.random()) + try: + conn._handle_dbapi_exception(Error(), "statement", {}, Mock(), Mock()) + except tsa.exc.DBAPIError: + pass + + # run an error + invalidate operation on the remaining 7 open connections + threads = [] + for conn in conns: + t = threading.Thread(target=attempt, args=(conn, )) + t.start() + threads.append(t) + + for t in threads: + t.join() + + # return all 15 connections to the pool + for conn in conns: + conn.close() + + # re-open 15 total connections + conns = [eng.connect() for i in range(15)] + + # 15 connections have been fully closed due to invalidate + assert slow_closing_connection._slow_close.call_count == 15 + + # 15 initial connections + 15 reconnections + assert slow_closing_connection.connect.call_count == 30 + assert len(pools) <= 2, len(pools) def test_invalidate(self): p = self._queuepool_fixture(pool_size=1, max_overflow=0) diff --git a/test/engine/test_reconnect.py b/test/engine/test_reconnect.py index ba336a1bfa..a3ad9c548a 100644 --- a/test/engine/test_reconnect.py +++ b/test/engine/test_reconnect.py @@ -146,16 +146,20 @@ class MockReconnectTest(fixtures.TestBase): # close shouldnt break conn.close() - is_not_(self.db.pool, db_pool) - - # ensure all connections closed (pool was recycled) + # ensure one connection closed... eq_( [c.close.mock_calls for c in self.dbapi.connections], - [[call()], [call()]] + [[call()], []] ) conn = self.db.connect() + + eq_( + [c.close.mock_calls for c in self.dbapi.connections], + [[call()], [call()], []] + ) + conn.execute(select([1])) conn.close() @@ -534,8 +538,6 @@ class RealReconnectTest(fixtures.TestBase): # invalidate() also doesn't screw up assert_raises(exc.DBAPIError, engine.connect) - # pool was recreated - assert engine.pool is not p1 def test_null_pool(self): engine = \