pool.py

SQLAlchemy. 经典的Python ORM框架。学习必看。

import testenv; testenv.configure_for_tests()
import threading, thread, time, gc
import sqlalchemy.pool as pool
import sqlalchemy.interfaces as interfaces
import sqlalchemy.exceptions as exceptions
from testlib import *


mcid = 1
class MockDBAPI(object):
    def __init__(self):
        self.throw_error = False
    def connect(self, argument, delay=0):
        if self.throw_error:
            raise Exception("couldnt connect !")
        if delay:
            time.sleep(delay)
        return MockConnection()
class MockConnection(object):
    def __init__(self):
        global mcid
        self.id = mcid
        self.closed = False
        mcid += 1
    def close(self):
        self.closed = True
    def rollback(self):
        pass
    def cursor(self):
        return MockCursor()
class MockCursor(object):
    def close(self):
        pass
mock_dbapi = MockDBAPI()

class PoolTest(TestBase):

    def setUp(self):
        pool.clear_managers()

    def testmanager(self):
        manager = pool.manage(mock_dbapi, use_threadlocal=True)

        connection = manager.connect('foo.db')
        connection2 = manager.connect('foo.db')
        connection3 = manager.connect('bar.db')

        print "connection " + repr(connection)
        self.assert_(connection.cursor() is not None)
        self.assert_(connection is connection2)
        self.assert_(connection2 is not connection3)

    def testbadargs(self):
        manager = pool.manage(mock_dbapi)

        try:
            connection = manager.connect(None)
        except:
            pass

    def testnonthreadlocalmanager(self):
        manager = pool.manage(mock_dbapi, use_threadlocal = False)

        connection = manager.connect('foo.db')
        connection2 = manager.connect('foo.db')

        print "connection " + repr(connection)

        self.assert_(connection.cursor() is not None)
        self.assert_(connection is not connection2)

    def testqueuepool_del(self):
        self._do_testqueuepool(useclose=False)

    def testqueuepool_close(self):
        self._do_testqueuepool(useclose=True)

    def _do_testqueuepool(self, useclose=False):
        p = pool.QueuePool(creator = lambda: mock_dbapi.connect('foo.db'), pool_size = 3, max_overflow = -1, use_threadlocal = False)

        def status(pool):
            tup = (pool.size(), pool.checkedin(), pool.overflow(), pool.checkedout())
            print "Pool size: %d  Connections in pool: %d Current Overflow: %d Current Checked out connections: %d" % tup
            return tup

        c1 = p.connect()
        self.assert_(status(p) == (3,0,-2,1))
        c2 = p.connect()
        self.assert_(status(p) == (3,0,-1,2))
        c3 = p.connect()
        self.assert_(status(p) == (3,0,0,3))
        c4 = p.connect()
        self.assert_(status(p) == (3,0,1,4))
        c5 = p.connect()
        self.assert_(status(p) == (3,0,2,5))
        c6 = p.connect()
        self.assert_(status(p) == (3,0,3,6))
        if useclose:
            c4.close()
            c3.close()
            c2.close()
        else:
            c4 = c3 = c2 = None
        self.assert_(status(p) == (3,3,3,3))
        if useclose:
            c1.close()
            c5.close()
            c6.close()
        else:
            c1 = c5 = c6 = None
        self.assert_(status(p) == (3,3,0,0))
        c1 = p.connect()
        c2 = p.connect()
        self.assert_(status(p) == (3, 1, 0, 2), status(p))
        if useclose:
            c2.close()
        else:
            c2 = None
        self.assert_(status(p) == (3, 2, 0, 1))

    def test_timeout(self):
        p = pool.QueuePool(creator = lambda: mock_dbapi.connect('foo.db'), pool_size = 3, max_overflow = 0, use_threadlocal = False, timeout=2)
        c1 = p.connect()
        c2 = p.connect()
        c3 = p.connect()
        now = time.time()
        try:
            c4 = p.connect()
            assert False
        except exceptions.TimeoutError, e:
            assert int(time.time() - now) == 2

    def test_timeout_race(self):
        # test a race condition where the initial connecting threads all race
        # to queue.Empty, then block on the mutex.  each thread consumes a
        # connection as they go in.  when the limit is reached, the remaining
        # threads go in, and get TimeoutError; even though they never got to
        # wait for the timeout on queue.get().  the fix involves checking the
        # timeout again within the mutex, and if so, unlocking and throwing
        # them back to the start of do_get()
        p = pool.QueuePool(creator = lambda: mock_dbapi.connect('foo.db', delay=.05), pool_size = 2, max_overflow = 1, use_threadlocal = False, timeout=3)
        timeouts = []
        def checkout():
            for x in xrange(1):
                now = time.time()
                try:
                    c1 = p.connect()
                except exceptions.TimeoutError, e:
                    timeouts.append(int(time.time()) - now)
                    continue
                time.sleep(4)
                c1.close()

        threads = []
        for i in xrange(10):
            th = threading.Thread(target=checkout)
            th.start()
            threads.append(th)
        for th in threads:
            th.join()

        print timeouts
        assert len(timeouts) > 0
        for t in timeouts:
            assert abs(t - 3) < 1, "Not all timeouts were 3 seconds: " + repr(timeouts)

    def _test_overflow(self, thread_count, max_overflow):
        def creator():
            time.sleep(.05)
            return mock_dbapi.connect('foo.db')

        p = pool.QueuePool(creator=creator,
                           pool_size=3, timeout=2,
                           max_overflow=max_overflow)
        peaks = []
        def whammy():
            for i in range(10):
                try:
                    con = p.connect()
                    time.sleep(.005)
                    peaks.append(p.overflow())
                    con.close()
                    del con
                except exceptions.TimeoutError:
                    pass
        threads = []
        for i in xrange(thread_count):
            th = threading.Thread(target=whammy)
            th.start()
            threads.append(th)
        for th in threads:
            th.join()

        self.assert_(max(peaks) <= max_overflow)

    def test_no_overflow(self):
        self._test_overflow(40, 0)

    def test_max_overflow(self):
        self._test_overflow(40, 5)

    def test_mixed_close(self):
        p = pool.QueuePool(creator = lambda: mock_dbapi.connect('foo.db'), pool_size = 3, max_overflow = -1, use_threadlocal = True)
        c1 = p.connect()
        c2 = p.connect()
        assert c1 is c2
        c1.close()
        c2 = None
        assert p.checkedout() == 1
        c1 = None
        assert p.checkedout() == 0

    def test_weakref_kaboom(self):
        p = pool.QueuePool(creator = lambda: mock_dbapi.connect('foo.db'), pool_size = 3, max_overflow = -1, use_threadlocal = True)
        c1 = p.connect()
        c2 = p.connect()
        c1.close()
        c2 = None
        del c1
        del c2
        gc.collect()
        assert p.checkedout() == 0
        c3 = p.connect()
        assert c3 is not None

    def test_trick_the_counter(self):
        """this is a "flaw" in the connection pool; since threadlocal uses a single ConnectionFairy per thread
        with an open/close counter, you can fool the counter into giving you a ConnectionFairy with an
        ambiguous counter.  i.e. its not true reference counting."""
        p = pool.QueuePool(creator = lambda: mock_dbapi.connect('foo.db'), pool_size = 3, max_overflow = -1, use_threadlocal = True)
        c1 = p.connect()
        c2 = p.connect()
        assert c1 is c2
        c1.close()
        c2 = p.connect()
        c2.close()
        self.assert_(p.checkedout() != 0)

        c2.close()
        self.assert_(p.checkedout() == 0)

    def test_recycle(self):
        p = pool.QueuePool(creator = lambda: mock_dbapi.connect('foo.db'), pool_size = 1, max_overflow = 0, use_threadlocal = False, recycle=3)

        c1 = p.connect()
        c_id = id(c1.connection)
        c1.close()
        c2 = p.connect()
        assert id(c2.connection) == c_id
        c2.close()
        time.sleep(4)
        c3= p.connect()
        assert id(c3.connection) != c_id

    def test_invalidate(self):
        dbapi = MockDBAPI()
        p = pool.QueuePool(creator = lambda: dbapi.connect('foo.db'), pool_size = 1, max_overflow = 0, use_threadlocal = False)
        c1 = p.connect()
        c_id = c1.connection.id
        c1.close(); c1=None
        c1 = p.connect()
        assert c1.connection.id == c_id
        c1.invalidate()
        c1 = None

        c1 = p.connect()
        assert c1.connection.id != c_id

    def test_recreate(self):
        dbapi = MockDBAPI()
        p = pool.QueuePool(creator = lambda: dbapi.connect('foo.db'), pool_size = 1, max_overflow = 0, use_threadlocal = False)
        p2 = p.recreate()
        assert p2.size() == 1
        assert p2._use_threadlocal is False
        assert p2._max_overflow == 0

    def test_reconnect(self):
        """tests reconnect operations at the pool level.  SA's engine/dialect includes another
        layer of reconnect support for 'database was lost' errors."""
        dbapi = MockDBAPI()