Beispiel #1
0
    def test_choosePerformerSorted(self):
        """
        If L{PeerConnectionPool.choosePerformer} is invoked make it
        return the peer with the least load.
        """
        peer = PeerConnectionPool(None, None, 4322, schema)

        class DummyPeer(object):
            def __init__(self, name, load):
                self.name = name
                self.load = load

            def currentLoadEstimate(self):
                return self.load

        apeer = DummyPeer("A", 1)
        bpeer = DummyPeer("B", 0)
        cpeer = DummyPeer("C", 2)
        peer.addPeerConnection(apeer)
        peer.addPeerConnection(bpeer)
        peer.addPeerConnection(cpeer)

        performer = peer.choosePerformer(onlyLocally=False)
        self.assertEqual(performer, bpeer)

        bpeer.load = 2
        performer = peer.choosePerformer(onlyLocally=False)
        self.assertEqual(performer, apeer)
    def test_choosePerformerSorted(self):
        """
        If L{PeerConnectionPool.choosePerformer} is invoked make it
        return the peer with the least load.
        """
        peer = PeerConnectionPool(None, None, 4322, schema)

        class DummyPeer(object):
            def __init__(self, name, load):
                self.name = name
                self.load = load

            def currentLoadEstimate(self):
                return self.load

        apeer = DummyPeer("A", 1)
        bpeer = DummyPeer("B", 0)
        cpeer = DummyPeer("C", 2)
        peer.addPeerConnection(apeer)
        peer.addPeerConnection(bpeer)
        peer.addPeerConnection(cpeer)

        performer = peer.choosePerformer(onlyLocally=False)
        self.assertEqual(performer, bpeer)

        bpeer.load = 2
        performer = peer.choosePerformer(onlyLocally=False)
        self.assertEqual(performer, apeer)
Beispiel #3
0
    def test_notBeforeBefore(self):
        """
        L{PeerConnectionPool.enqueueWork} will execute its work immediately if
        the C{notBefore} attribute of the work item in question is in the past.
        """
        dbpool = buildConnectionPool(self, schemaText + nodeSchema)
        fakeNow = datetime.datetime(2012, 12, 12, 12, 12, 12)
        sinceEpoch = astimestamp(fakeNow)
        clock = Clock()
        clock.advance(sinceEpoch)
        qpool = PeerConnectionPool(clock, dbpool.connection, 0, schema)
        realChoosePerformer = qpool.choosePerformer
        performerChosen = []
        def catchPerformerChoice():
            result = realChoosePerformer()
            performerChosen.append(True)
            return result
        qpool.choosePerformer = catchPerformerChoice
        @transactionally(dbpool.connection)
        def check(txn):
            return qpool.enqueueWork(
                txn, DummyWorkItem, a=3, b=9,
                notBefore=datetime.datetime(2012, 12, 12, 12, 12, 0)
            ).whenProposed()
        proposal = yield check

        clock.advance(1000)
        # Advance far beyond the given timestamp.
        self.assertEquals(performerChosen, [True])

        result = yield proposal.whenExecuted()
        self.assertIdentical(result, proposal)
Beispiel #4
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 def test_performingWorkOnNetwork(self):
     """
     The L{PerformWork} command will get relayed to the remote peer
     controller.
     """
     peer = PeerConnectionPool(None, None, 4322, schema)
     local = self.pcp.peerFactory().buildProtocol(None)
     remote = peer.peerFactory().buildProtocol(None)
     connection = Connection(local, remote)
     connection.start()
     d = Deferred()
     class DummyPerformer(object):
         def performWork(self, table, workID):
             self.table = table
             self.workID = workID
             return d
     # Doing real database I/O in this test would be tedious so fake the
     # first method in the call stack which actually talks to the DB.
     dummy = DummyPerformer()
     def chooseDummy(onlyLocally=False):
         return dummy
     peer.choosePerformer = chooseDummy
     performed = local.performWork(schema.DUMMY_WORK_ITEM, 7384)
     performResult = []
     performed.addCallback(performResult.append)
     # Sanity check.
     self.assertEquals(performResult, [])
     connection.flush()
     self.assertEquals(dummy.table, schema.DUMMY_WORK_ITEM)
     self.assertEquals(dummy.workID, 7384)
     self.assertEquals(performResult, [])
     d.callback(128374)
     connection.flush()
     self.assertEquals(performResult, [None])
Beispiel #5
0
    def test_notBeforeWhenEnqueueing(self):
        """
        L{PeerConnectionPool.enqueueWork} enqueues some work immediately, but
        only executes it when enough time has elapsed to allow the C{notBefore}
        attribute of the given work item to have passed.
        """
        dbpool = buildConnectionPool(self, schemaText + nodeSchema)
        fakeNow = datetime.datetime(2012, 12, 12, 12, 12, 12)
        sinceEpoch = astimestamp(fakeNow)
        clock = Clock()
        clock.advance(sinceEpoch)
        qpool = PeerConnectionPool(clock, dbpool.connection, 0, schema)
        realChoosePerformer = qpool.choosePerformer
        performerChosen = []

        def catchPerformerChoice():
            result = realChoosePerformer()
            performerChosen.append(True)
            return result

        qpool.choosePerformer = catchPerformerChoice

        @transactionally(dbpool.connection)
        def check(txn):
            return qpool.enqueueWork(txn,
                                     DummyWorkItem,
                                     a=3,
                                     b=9,
                                     notBefore=datetime.datetime(
                                         2012, 12, 12, 12, 12,
                                         20)).whenProposed()

        proposal = yield check

        # This is going to schedule the work to happen with some asynchronous
        # I/O in the middle; this is a problem because how do we know when it's
        # time to check to see if the work has started?  We need to intercept
        # the thing that kicks off the work; we can then wait for the work
        # itself.

        self.assertEquals(performerChosen, [])

        # Advance to exactly the appointed second.
        clock.advance(20 - 12)
        self.assertEquals(performerChosen, [True])

        # FIXME: if this fails, it will hang, but that's better than no
        # notification that it is broken at all.

        result = yield proposal.whenExecuted()
        self.assertIdentical(result, proposal)
Beispiel #6
0
    def test_notBeforeWhenEnqueueing(self):
        """
        L{PeerConnectionPool.enqueueWork} enqueues some work immediately, but
        only executes it when enough time has elapsed to allow the C{notBefore}
        attribute of the given work item to have passed.
        """
        dbpool = buildConnectionPool(self, schemaText + nodeSchema)
        fakeNow = datetime.datetime(2012, 12, 12, 12, 12, 12)
        sinceEpoch = astimestamp(fakeNow)
        clock = Clock()
        clock.advance(sinceEpoch)
        qpool = PeerConnectionPool(clock, dbpool.connection, 0, schema)
        realChoosePerformer = qpool.choosePerformer
        performerChosen = []
        def catchPerformerChoice():
            result = realChoosePerformer()
            performerChosen.append(True)
            return result
        qpool.choosePerformer = catchPerformerChoice
        @transactionally(dbpool.connection)
        def check(txn):
            return qpool.enqueueWork(
                txn, DummyWorkItem, a=3, b=9,
                notBefore=datetime.datetime(2012, 12, 12, 12, 12, 20)
            ).whenProposed()

        proposal = yield check

        # This is going to schedule the work to happen with some asynchronous
        # I/O in the middle; this is a problem because how do we know when it's
        # time to check to see if the work has started?  We need to intercept
        # the thing that kicks off the work; we can then wait for the work
        # itself.

        self.assertEquals(performerChosen, [])

        # Advance to exactly the appointed second.
        clock.advance(20 - 12)
        self.assertEquals(performerChosen, [True])

        # FIXME: if this fails, it will hang, but that's better than no
        # notification that it is broken at all.

        result = yield proposal.whenExecuted()
        self.assertIdentical(result, proposal)
Beispiel #7
0
    def test_notBeforeBefore(self):
        """
        L{PeerConnectionPool.enqueueWork} will execute its work immediately if
        the C{notBefore} attribute of the work item in question is in the past.
        """
        dbpool = buildConnectionPool(self, schemaText + nodeSchema)
        fakeNow = datetime.datetime(2012, 12, 12, 12, 12, 12)
        sinceEpoch = astimestamp(fakeNow)
        clock = Clock()
        clock.advance(sinceEpoch)
        qpool = PeerConnectionPool(clock, dbpool.connection, 0, schema)
        realChoosePerformer = qpool.choosePerformer
        performerChosen = []

        def catchPerformerChoice():
            result = realChoosePerformer()
            performerChosen.append(True)
            return result

        qpool.choosePerformer = catchPerformerChoice

        @transactionally(dbpool.connection)
        def check(txn):
            return qpool.enqueueWork(txn,
                                     DummyWorkItem,
                                     a=3,
                                     b=9,
                                     notBefore=datetime.datetime(
                                         2012, 12, 12, 12, 12,
                                         0)).whenProposed()

        proposal = yield check

        clock.advance(1000)
        # Advance far beyond the given timestamp.
        self.assertEquals(performerChosen, [True])

        result = yield proposal.whenExecuted()
        self.assertIdentical(result, proposal)
Beispiel #8
0
    def test_performingWorkOnNetwork(self):
        """
        The L{PerformWork} command will get relayed to the remote peer
        controller.
        """
        peer = PeerConnectionPool(None, None, 4322, schema)
        local = self.pcp.peerFactory().buildProtocol(None)
        remote = peer.peerFactory().buildProtocol(None)
        connection = Connection(local, remote)
        connection.start()
        d = Deferred()

        class DummyPerformer(object):
            def performWork(self, table, workID):
                self.table = table
                self.workID = workID
                return d

        # Doing real database I/O in this test would be tedious so fake the
        # first method in the call stack which actually talks to the DB.
        dummy = DummyPerformer()

        def chooseDummy(onlyLocally=False):
            return dummy

        peer.choosePerformer = chooseDummy
        performed = local.performWork(schema.DUMMY_WORK_ITEM, 7384)
        performResult = []
        performed.addCallback(performResult.append)

        # Sanity check.
        self.assertEquals(performResult, [])
        connection.flush()
        self.assertEquals(dummy.table, schema.DUMMY_WORK_ITEM)
        self.assertEquals(dummy.workID, 7384)
        self.assertEquals(performResult, [])
        d.callback(128374)
        connection.flush()
        self.assertEquals(performResult, [None])
Beispiel #9
0
class PeerConnectionPoolUnitTests(TestCase):
    """
    L{PeerConnectionPool} has many internal components.
    """
    def setUp(self):
        """
        Create a L{PeerConnectionPool} that is just initialized enough.
        """
        self.pcp = PeerConnectionPool(None, None, 4321, schema)

    def checkPerformer(self, cls):
        """
        Verify that the performer returned by
        L{PeerConnectionPool.choosePerformer}.
        """
        performer = self.pcp.choosePerformer()
        self.failUnlessIsInstance(performer, cls)
        verifyObject(_IWorkPerformer, performer)

    def test_choosingPerformerWhenNoPeersAndNoWorkers(self):
        """
        If L{PeerConnectionPool.choosePerformer} is invoked when no workers
        have spawned and no peers have established connections (either incoming
        or outgoing), then it chooses an implementation of C{performWork} that
        simply executes the work locally.
        """
        self.checkPerformer(LocalPerformer)

    def test_choosingPerformerWithLocalCapacity(self):
        """
        If L{PeerConnectionPool.choosePerformer} is invoked when some workers
        have spawned, then it should choose the worker pool as the local
        performer.
        """
        # Give it some local capacity.
        wlf = self.pcp.workerListenerFactory()
        proto = wlf.buildProtocol(None)
        proto.makeConnection(StringTransport())
        # Sanity check.
        self.assertEqual(len(self.pcp.workerPool.workers), 1)
        self.assertEqual(self.pcp.workerPool.hasAvailableCapacity(), True)
        # Now it has some capacity.
        self.checkPerformer(WorkerConnectionPool)

    def test_choosingPerformerFromNetwork(self):
        """
        If L{PeerConnectionPool.choosePerformer} is invoked when no workers
        have spawned but some peers have connected, then it should choose a
        connection from the network to perform it.
        """
        peer = PeerConnectionPool(None, None, 4322, schema)
        local = self.pcp.peerFactory().buildProtocol(None)
        remote = peer.peerFactory().buildProtocol(None)
        connection = Connection(local, remote)
        connection.start()
        self.checkPerformer(ConnectionFromPeerNode)

    def test_performingWorkOnNetwork(self):
        """
        The L{PerformWork} command will get relayed to the remote peer
        controller.
        """
        peer = PeerConnectionPool(None, None, 4322, schema)
        local = self.pcp.peerFactory().buildProtocol(None)
        remote = peer.peerFactory().buildProtocol(None)
        connection = Connection(local, remote)
        connection.start()
        d = Deferred()

        class DummyPerformer(object):
            def performWork(self, table, workID):
                self.table = table
                self.workID = workID
                return d

        # Doing real database I/O in this test would be tedious so fake the
        # first method in the call stack which actually talks to the DB.
        dummy = DummyPerformer()

        def chooseDummy(onlyLocally=False):
            return dummy

        peer.choosePerformer = chooseDummy
        performed = local.performWork(schema.DUMMY_WORK_ITEM, 7384)
        performResult = []
        performed.addCallback(performResult.append)

        # Sanity check.
        self.assertEquals(performResult, [])
        connection.flush()
        self.assertEquals(dummy.table, schema.DUMMY_WORK_ITEM)
        self.assertEquals(dummy.workID, 7384)
        self.assertEquals(performResult, [])
        d.callback(128374)
        connection.flush()
        self.assertEquals(performResult, [None])

    def test_choosePerformerSorted(self):
        """
        If L{PeerConnectionPool.choosePerformer} is invoked make it
        return the peer with the least load.
        """
        peer = PeerConnectionPool(None, None, 4322, schema)

        class DummyPeer(object):
            def __init__(self, name, load):
                self.name = name
                self.load = load

            def currentLoadEstimate(self):
                return self.load

        apeer = DummyPeer("A", 1)
        bpeer = DummyPeer("B", 0)
        cpeer = DummyPeer("C", 2)
        peer.addPeerConnection(apeer)
        peer.addPeerConnection(bpeer)
        peer.addPeerConnection(cpeer)

        performer = peer.choosePerformer(onlyLocally=False)
        self.assertEqual(performer, bpeer)

        bpeer.load = 2
        performer = peer.choosePerformer(onlyLocally=False)
        self.assertEqual(performer, apeer)

    @inlineCallbacks
    def test_notBeforeWhenCheckingForLostWork(self):
        """
        L{PeerConnectionPool._periodicLostWorkCheck} should execute any
        outstanding work items, but only those that are expired.
        """
        dbpool = buildConnectionPool(self, schemaText + nodeSchema)
        # An arbitrary point in time.
        fakeNow = datetime.datetime(2012, 12, 12, 12, 12, 12)
        # *why* does datetime still not have .astimestamp()
        sinceEpoch = astimestamp(fakeNow)
        clock = Clock()
        clock.advance(sinceEpoch)
        qpool = PeerConnectionPool(clock, dbpool.connection, 0, schema)

        # Let's create a couple of work items directly, not via the enqueue
        # method, so that they exist but nobody will try to immediately execute
        # them.

        @transactionally(dbpool.connection)
        @inlineCallbacks
        def setup(txn):
            # First, one that's right now.
            yield DummyWorkItem.create(txn, a=1, b=2, notBefore=fakeNow)

            # Next, create one that's actually far enough into the past to run.
            yield DummyWorkItem.create(
                txn,
                a=3,
                b=4,
                notBefore=(
                    # Schedule it in the past so that it should have already
                    # run.
                    fakeNow - datetime.timedelta(
                        seconds=qpool.queueProcessTimeout + 20)))

            # Finally, one that's actually scheduled for the future.
            yield DummyWorkItem.create(txn,
                                       a=10,
                                       b=20,
                                       notBefore=fakeNow +
                                       datetime.timedelta(1000))

        yield setup
        qpool.running = True
        yield qpool._periodicLostWorkCheck()

        @transactionally(dbpool.connection)
        def check(txn):
            return DummyWorkDone.all(txn)

        every = yield check
        self.assertEquals([x.aPlusB for x in every], [7])

    @inlineCallbacks
    def test_notBeforeWhenEnqueueing(self):
        """
        L{PeerConnectionPool.enqueueWork} enqueues some work immediately, but
        only executes it when enough time has elapsed to allow the C{notBefore}
        attribute of the given work item to have passed.
        """
        dbpool = buildConnectionPool(self, schemaText + nodeSchema)
        fakeNow = datetime.datetime(2012, 12, 12, 12, 12, 12)
        sinceEpoch = astimestamp(fakeNow)
        clock = Clock()
        clock.advance(sinceEpoch)
        qpool = PeerConnectionPool(clock, dbpool.connection, 0, schema)
        realChoosePerformer = qpool.choosePerformer
        performerChosen = []

        def catchPerformerChoice():
            result = realChoosePerformer()
            performerChosen.append(True)
            return result

        qpool.choosePerformer = catchPerformerChoice

        @transactionally(dbpool.connection)
        def check(txn):
            return qpool.enqueueWork(txn,
                                     DummyWorkItem,
                                     a=3,
                                     b=9,
                                     notBefore=datetime.datetime(
                                         2012, 12, 12, 12, 12,
                                         20)).whenProposed()

        proposal = yield check

        # This is going to schedule the work to happen with some asynchronous
        # I/O in the middle; this is a problem because how do we know when it's
        # time to check to see if the work has started?  We need to intercept
        # the thing that kicks off the work; we can then wait for the work
        # itself.

        self.assertEquals(performerChosen, [])

        # Advance to exactly the appointed second.
        clock.advance(20 - 12)
        self.assertEquals(performerChosen, [True])

        # FIXME: if this fails, it will hang, but that's better than no
        # notification that it is broken at all.

        result = yield proposal.whenExecuted()
        self.assertIdentical(result, proposal)

    @inlineCallbacks
    def test_notBeforeBefore(self):
        """
        L{PeerConnectionPool.enqueueWork} will execute its work immediately if
        the C{notBefore} attribute of the work item in question is in the past.
        """
        dbpool = buildConnectionPool(self, schemaText + nodeSchema)
        fakeNow = datetime.datetime(2012, 12, 12, 12, 12, 12)
        sinceEpoch = astimestamp(fakeNow)
        clock = Clock()
        clock.advance(sinceEpoch)
        qpool = PeerConnectionPool(clock, dbpool.connection, 0, schema)
        realChoosePerformer = qpool.choosePerformer
        performerChosen = []

        def catchPerformerChoice():
            result = realChoosePerformer()
            performerChosen.append(True)
            return result

        qpool.choosePerformer = catchPerformerChoice

        @transactionally(dbpool.connection)
        def check(txn):
            return qpool.enqueueWork(txn,
                                     DummyWorkItem,
                                     a=3,
                                     b=9,
                                     notBefore=datetime.datetime(
                                         2012, 12, 12, 12, 12,
                                         0)).whenProposed()

        proposal = yield check

        clock.advance(1000)
        # Advance far beyond the given timestamp.
        self.assertEquals(performerChosen, [True])

        result = yield proposal.whenExecuted()
        self.assertIdentical(result, proposal)

    def test_workerConnectionPoolPerformWork(self):
        """
        L{WorkerConnectionPool.performWork} performs work by selecting a
        L{ConnectionFromWorker} and sending it a L{PerformWork} command.
        """
        clock = Clock()
        peerPool = PeerConnectionPool(clock, None, 4322, schema)
        factory = peerPool.workerListenerFactory()

        def peer():
            p = factory.buildProtocol(None)
            t = StringTransport()
            p.makeConnection(t)
            return p, t

        worker1, _ignore_trans1 = peer()
        worker2, _ignore_trans2 = peer()

        # Ask the worker to do something.
        worker1.performWork(schema.DUMMY_WORK_ITEM, 1)
        self.assertEquals(worker1.currentLoad, 1)
        self.assertEquals(worker2.currentLoad, 0)

        # Now ask the pool to do something
        peerPool.workerPool.performWork(schema.DUMMY_WORK_ITEM, 2)
        self.assertEquals(worker1.currentLoad, 1)
        self.assertEquals(worker2.currentLoad, 1)

    def test_poolStartServiceChecksForWork(self):
        """
        L{PeerConnectionPool.startService} kicks off the idle work-check loop.
        """
        reactor = MemoryReactorWithClock()
        cph = SteppablePoolHelper(nodeSchema + schemaText)
        then = datetime.datetime(2012, 12, 12, 12, 12, 0)
        reactor.advance(astimestamp(then))
        cph.setUp(self)
        pcp = PeerConnectionPool(reactor, cph.pool.connection, 4321, schema)
        now = then + datetime.timedelta(seconds=pcp.queueProcessTimeout * 2)

        @transactionally(cph.pool.connection)
        def createOldWork(txn):
            one = DummyWorkItem.create(txn, workID=1, a=3, b=4, notBefore=then)
            two = DummyWorkItem.create(txn, workID=2, a=7, b=9, notBefore=now)
            return gatherResults([one, two])

        pcp.startService()
        cph.flushHolders()
        reactor.advance(pcp.queueProcessTimeout * 2)
        self.assertEquals(cph.rows("select * from DUMMY_WORK_DONE"), [(1, 7)])
        cph.rows("delete from DUMMY_WORK_DONE")
        reactor.advance(pcp.queueProcessTimeout * 2)
        self.assertEquals(cph.rows("select * from DUMMY_WORK_DONE"), [(2, 16)])
Beispiel #10
0
class PeerConnectionPoolUnitTests(TestCase):
    """
    L{PeerConnectionPool} has many internal components.
    """
    def setUp(self):
        """
        Create a L{PeerConnectionPool} that is just initialized enough.
        """
        self.pcp = PeerConnectionPool(None, None, 4321, schema)


    def checkPerformer(self, cls):
        """
        Verify that the performer returned by
        L{PeerConnectionPool.choosePerformer}.
        """
        performer = self.pcp.choosePerformer()
        self.failUnlessIsInstance(performer, cls)
        verifyObject(_IWorkPerformer, performer)


    def test_choosingPerformerWhenNoPeersAndNoWorkers(self):
        """
        If L{PeerConnectionPool.choosePerformer} is invoked when no workers
        have spawned and no peers have established connections (either incoming
        or outgoing), then it chooses an implementation of C{performWork} that
        simply executes the work locally.
        """
        self.checkPerformer(LocalPerformer)


    def test_choosingPerformerWithLocalCapacity(self):
        """
        If L{PeerConnectionPool.choosePerformer} is invoked when some workers
        have spawned, then it should choose the worker pool as the local
        performer.
        """
        # Give it some local capacity.
        wlf = self.pcp.workerListenerFactory()
        proto = wlf.buildProtocol(None)
        proto.makeConnection(StringTransport())
        # Sanity check.
        self.assertEqual(len(self.pcp.workerPool.workers), 1)
        self.assertEqual(self.pcp.workerPool.hasAvailableCapacity(), True)
        # Now it has some capacity.
        self.checkPerformer(WorkerConnectionPool)


    def test_choosingPerformerFromNetwork(self):
        """
        If L{PeerConnectionPool.choosePerformer} is invoked when no workers
        have spawned but some peers have connected, then it should choose a
        connection from the network to perform it.
        """
        peer = PeerConnectionPool(None, None, 4322, schema)
        local = self.pcp.peerFactory().buildProtocol(None)
        remote = peer.peerFactory().buildProtocol(None)
        connection = Connection(local, remote)
        connection.start()
        self.checkPerformer(ConnectionFromPeerNode)


    def test_performingWorkOnNetwork(self):
        """
        The L{PerformWork} command will get relayed to the remote peer
        controller.
        """
        peer = PeerConnectionPool(None, None, 4322, schema)
        local = self.pcp.peerFactory().buildProtocol(None)
        remote = peer.peerFactory().buildProtocol(None)
        connection = Connection(local, remote)
        connection.start()
        d = Deferred()
        class DummyPerformer(object):
            def performWork(self, table, workID):
                self.table = table
                self.workID = workID
                return d
        # Doing real database I/O in this test would be tedious so fake the
        # first method in the call stack which actually talks to the DB.
        dummy = DummyPerformer()
        def chooseDummy(onlyLocally=False):
            return dummy
        peer.choosePerformer = chooseDummy
        performed = local.performWork(schema.DUMMY_WORK_ITEM, 7384)
        performResult = []
        performed.addCallback(performResult.append)
        # Sanity check.
        self.assertEquals(performResult, [])
        connection.flush()
        self.assertEquals(dummy.table, schema.DUMMY_WORK_ITEM)
        self.assertEquals(dummy.workID, 7384)
        self.assertEquals(performResult, [])
        d.callback(128374)
        connection.flush()
        self.assertEquals(performResult, [None])


    @inlineCallbacks
    def test_notBeforeWhenCheckingForLostWork(self):
        """
        L{PeerConnectionPool._periodicLostWorkCheck} should execute any
        outstanding work items, but only those that are expired.
        """
        dbpool = buildConnectionPool(self, schemaText + nodeSchema)
        # An arbitrary point in time.
        fakeNow = datetime.datetime(2012, 12, 12, 12, 12, 12)
        # *why* does datetime still not have .astimestamp()
        sinceEpoch = astimestamp(fakeNow)
        clock = Clock()
        clock.advance(sinceEpoch)
        qpool = PeerConnectionPool(clock, dbpool.connection, 0, schema)

        # Let's create a couple of work items directly, not via the enqueue
        # method, so that they exist but nobody will try to immediately execute
        # them.

        @transactionally(dbpool.connection)
        @inlineCallbacks
        def setup(txn):
            # First, one that's right now.
            yield DummyWorkItem.create(txn, a=1, b=2, notBefore=fakeNow)

            # Next, create one that's actually far enough into the past to run.
            yield DummyWorkItem.create(
                txn, a=3, b=4, notBefore=(
                    # Schedule it in the past so that it should have already run.
                    fakeNow - datetime.timedelta(
                        seconds=qpool.queueProcessTimeout + 20
                    )
                )
            )

            # Finally, one that's actually scheduled for the future.
            yield DummyWorkItem.create(
                txn, a=10, b=20, notBefore=fakeNow + datetime.timedelta(1000)
            )
        yield setup
        yield qpool._periodicLostWorkCheck()
        @transactionally(dbpool.connection)
        def check(txn):
            return DummyWorkDone.all(txn)
        every = yield check
        self.assertEquals([x.aPlusB for x in every], [7])


    @inlineCallbacks
    def test_notBeforeWhenEnqueueing(self):
        """
        L{PeerConnectionPool.enqueueWork} enqueues some work immediately, but
        only executes it when enough time has elapsed to allow the C{notBefore}
        attribute of the given work item to have passed.
        """
        dbpool = buildConnectionPool(self, schemaText + nodeSchema)
        fakeNow = datetime.datetime(2012, 12, 12, 12, 12, 12)
        sinceEpoch = astimestamp(fakeNow)
        clock = Clock()
        clock.advance(sinceEpoch)
        qpool = PeerConnectionPool(clock, dbpool.connection, 0, schema)
        realChoosePerformer = qpool.choosePerformer
        performerChosen = []
        def catchPerformerChoice():
            result = realChoosePerformer()
            performerChosen.append(True)
            return result
        qpool.choosePerformer = catchPerformerChoice
        @transactionally(dbpool.connection)
        def check(txn):
            return qpool.enqueueWork(
                txn, DummyWorkItem, a=3, b=9,
                notBefore=datetime.datetime(2012, 12, 12, 12, 12, 20)
            ).whenProposed()

        proposal = yield check

        # This is going to schedule the work to happen with some asynchronous
        # I/O in the middle; this is a problem because how do we know when it's
        # time to check to see if the work has started?  We need to intercept
        # the thing that kicks off the work; we can then wait for the work
        # itself.

        self.assertEquals(performerChosen, [])

        # Advance to exactly the appointed second.
        clock.advance(20 - 12)
        self.assertEquals(performerChosen, [True])

        # FIXME: if this fails, it will hang, but that's better than no
        # notification that it is broken at all.

        result = yield proposal.whenExecuted()
        self.assertIdentical(result, proposal)


    @inlineCallbacks
    def test_notBeforeBefore(self):
        """
        L{PeerConnectionPool.enqueueWork} will execute its work immediately if
        the C{notBefore} attribute of the work item in question is in the past.
        """
        dbpool = buildConnectionPool(self, schemaText + nodeSchema)
        fakeNow = datetime.datetime(2012, 12, 12, 12, 12, 12)
        sinceEpoch = astimestamp(fakeNow)
        clock = Clock()
        clock.advance(sinceEpoch)
        qpool = PeerConnectionPool(clock, dbpool.connection, 0, schema)
        realChoosePerformer = qpool.choosePerformer
        performerChosen = []
        def catchPerformerChoice():
            result = realChoosePerformer()
            performerChosen.append(True)
            return result
        qpool.choosePerformer = catchPerformerChoice
        @transactionally(dbpool.connection)
        def check(txn):
            return qpool.enqueueWork(
                txn, DummyWorkItem, a=3, b=9,
                notBefore=datetime.datetime(2012, 12, 12, 12, 12, 0)
            ).whenProposed()
        proposal = yield check

        clock.advance(1000)
        # Advance far beyond the given timestamp.
        self.assertEquals(performerChosen, [True])

        result = yield proposal.whenExecuted()
        self.assertIdentical(result, proposal)