test_leaks.py

# -*- coding: utf-8 -*-
"""
Testing scenarios that may have leaked.
"""
from __future__ import print_function, absolute_import, division

import sys
import gc

import time
import weakref
import threading

import psutil

import greenlet
from . import TestCase
from .leakcheck import fails_leakcheck
from .leakcheck import ignores_leakcheck

try:
    from sys import intern
except ImportError:
    # Python 2
    pass

assert greenlet.GREENLET_USE_GC # Option to disable this was removed in 1.0

class HasFinalizerTracksInstances(object):
    EXTANT_INSTANCES = set()
    def __init__(self, msg):
        self.msg = intern(msg)
        self.EXTANT_INSTANCES.add(id(self))
    def __del__(self):
        self.EXTANT_INSTANCES.remove(id(self))
    def __repr__(self):
        return "<HasFinalizerTracksInstances at 0x%x %r>" % (
            id(self), self.msg
        )
    @classmethod
    def reset(cls):
        cls.EXTANT_INSTANCES.clear()


class TestLeaks(TestCase):

    def test_arg_refs(self):
        args = ('a', 'b', 'c')
        refcount_before = sys.getrefcount(args)
        # pylint:disable=unnecessary-lambda
        g = greenlet.greenlet(
            lambda *args: greenlet.getcurrent().parent.switch(*args))
        for _ in range(100):
            g.switch(*args)
        self.assertEqual(sys.getrefcount(args), refcount_before)

    def test_kwarg_refs(self):
        kwargs = {}
        # pylint:disable=unnecessary-lambda
        g = greenlet.greenlet(
            lambda **kwargs: greenlet.getcurrent().parent.switch(**kwargs))
        for _ in range(100):
            g.switch(**kwargs)
        self.assertEqual(sys.getrefcount(kwargs), 2)


    @staticmethod
    def __recycle_threads():
        # By introducing a thread that does sleep we allow other threads,
        # that have triggered their __block condition, but did not have a
        # chance to deallocate their thread state yet, to finally do so.
        # The way it works is by requiring a GIL switch (different thread),
        # which does a GIL release (sleep), which might do a GIL switch
        # to finished threads and allow them to clean up.
        def worker():
            time.sleep(0.001)
        t = threading.Thread(target=worker)
        t.start()
        time.sleep(0.001)
        t.join(10)

    def test_threaded_leak(self):
        gg = []
        def worker():
            # only main greenlet present
            gg.append(weakref.ref(greenlet.getcurrent()))
        for _ in range(2):
            t = threading.Thread(target=worker)
            t.start()
            t.join(10)
            del t
        greenlet.getcurrent() # update ts_current
        self.__recycle_threads()
        greenlet.getcurrent() # update ts_current
        gc.collect()
        greenlet.getcurrent() # update ts_current
        for g in gg:
            self.assertIsNone(g())

    def test_threaded_adv_leak(self):
        gg = []
        def worker():
            # main and additional *finished* greenlets
            ll = greenlet.getcurrent().ll = []
            def additional():
                ll.append(greenlet.getcurrent())
            for _ in range(2):
                greenlet.greenlet(additional).switch()
            gg.append(weakref.ref(greenlet.getcurrent()))
        for _ in range(2):
            t = threading.Thread(target=worker)
            t.start()
            t.join(10)
            del t
        greenlet.getcurrent() # update ts_current
        self.__recycle_threads()
        greenlet.getcurrent() # update ts_current
        gc.collect()
        greenlet.getcurrent() # update ts_current
        for g in gg:
            self.assertIsNone(g())

    def assertClocksUsed(self):
        used = greenlet._greenlet.get_clocks_used_doing_optional_cleanup()
        self.assertGreaterEqual(used, 0)
        # we don't lose the value
        greenlet._greenlet.enable_optional_cleanup(True)
        used2 = greenlet._greenlet.get_clocks_used_doing_optional_cleanup()
        self.assertEqual(used, used2)
        self.assertGreater(greenlet._greenlet.CLOCKS_PER_SEC, 1)

    def _check_issue251(self,
                        manually_collect_background=True,
                        explicit_reference_to_switch=False):
        # See https://github.com/python-greenlet/greenlet/issues/251
        # Killing a greenlet (probably not the main one)
        # in one thread from another thread would
        # result in leaking a list (the ts_delkey list).
        # We no longer use lists to hold that stuff, though.

        # For the test to be valid, even empty lists have to be tracked by the
        # GC

        assert gc.is_tracked([])
        HasFinalizerTracksInstances.reset()
        greenlet.getcurrent()
        greenlets_before = self.count_objects(greenlet.greenlet, exact_kind=False)

        background_glet_running = threading.Event()
        background_glet_killed = threading.Event()
        background_greenlets = []

        # XXX: Switching this to a greenlet subclass that overrides
        # run results in all callers failing the leaktest; that
        # greenlet instance is leaked. There's a bound method for
        # run() living on the stack of the greenlet in g_initialstub,
        # and since we don't manually switch back to the background
        # greenlet to let it "fall off the end" and exit the
        # g_initialstub function, it never gets cleaned up. Making the
        # garbage collector aware of this bound method (making it an
        # attribute of the greenlet structure and traversing into it)
        # doesn't help, for some reason.
        def background_greenlet():
            # Throw control back to the main greenlet.
            jd = HasFinalizerTracksInstances("DELETING STACK OBJECT")
            greenlet._greenlet.set_thread_local(
                'test_leaks_key',
                HasFinalizerTracksInstances("DELETING THREAD STATE"))
            # Explicitly keeping 'switch' in a local variable
            # breaks this test in all versions
            if explicit_reference_to_switch:
                s = greenlet.getcurrent().parent.switch
                s([jd])
            else:
                greenlet.getcurrent().parent.switch([jd])

        bg_main_wrefs = []

        def background_thread():
            glet = greenlet.greenlet(background_greenlet)
            bg_main_wrefs.append(weakref.ref(glet.parent))

            background_greenlets.append(glet)
            glet.switch() # Be sure it's active.
            # Control is ours again.
            del glet # Delete one reference from the thread it runs in.
            background_glet_running.set()
            background_glet_killed.wait(10)

            # To trigger the background collection of the dead
            # greenlet, thus clearing out the contents of the list, we
            # need to run some APIs. See issue 252.
            if manually_collect_background:
                greenlet.getcurrent()


        t = threading.Thread(target=background_thread)
        t.start()
        background_glet_running.wait(10)
        greenlet.getcurrent()
        lists_before = self.count_objects(list, exact_kind=True)

        assert len(background_greenlets) == 1
        self.assertFalse(background_greenlets[0].dead)
        # Delete the last reference to the background greenlet
        # from a different thread. This puts it in the background thread's
        # ts_delkey list.
        del background_greenlets[:]
        background_glet_killed.set()

        # Now wait for the background thread to die.
        t.join(10)
        del t
        # As part of the fix for 252, we need to cycle the ceval.c
        # interpreter loop to be sure it has had a chance to process
        # the pending call.
        self.wait_for_pending_cleanups()

        lists_after = self.count_objects(list, exact_kind=True)
        greenlets_after = self.count_objects(greenlet.greenlet, exact_kind=False)

        # On 2.7, we observe that lists_after is smaller than
        # lists_before. No idea what lists got cleaned up. All the
        # Python 3 versions match exactly.
        self.assertLessEqual(lists_after, lists_before)
        # On versions after 3.6, we've successfully cleaned up the
        # greenlet references thanks to the internal "vectorcall"
        # protocol; prior to that, there is a reference path through
        # the ``greenlet.switch`` method still on the stack that we
        # can't reach to clean up. The C code goes through terrific
        # lengths to clean that up.
        if not explicit_reference_to_switch and greenlet._greenlet.get_clocks_used_doing_optional_cleanup() is not None:
            # If cleanup was disabled, though, we may not find it.
            self.assertEqual(greenlets_after, greenlets_before)
            if manually_collect_background:
                # TODO: Figure out how to make this work!
                # The one on the stack is still leaking somehow
                # in the non-manually-collect state.
                self.assertEqual(HasFinalizerTracksInstances.EXTANT_INSTANCES, set())
        else:
            # The explicit reference prevents us from collecting it
            # and it isn't always found by the GC either for some
            # reason. The entire frame is leaked somehow, on some
            # platforms (e.g., MacPorts builds of Python (all
            # versions!)), but not on other platforms (the linux and
            # windows builds on GitHub actions and Appveyor). So we'd
            # like to write a test that proves that the main greenlet
            # sticks around, and we can on my machine (macOS 11.6,
            # MacPorts builds of everything) but we can't write that
            # same test on other platforms. However, hopefully iteration
            # done by leakcheck will find it.
            pass

        if greenlet._greenlet.get_clocks_used_doing_optional_cleanup() is not None:
            self.assertClocksUsed()

    def test_issue251_killing_cross_thread_leaks_list(self):
        self._check_issue251()

    def test_issue251_with_cleanup_disabled(self):
        greenlet._greenlet.enable_optional_cleanup(False)
        try:
            self._check_issue251()
        finally:
            greenlet._greenlet.enable_optional_cleanup(True)

    @fails_leakcheck
    def test_issue251_issue252_need_to_collect_in_background(self):
        # Between greenlet 1.1.2 and the next version, this was still
        # failing because the leak of the list still exists when we
        # don't call a greenlet API before exiting the thread. The
        # proximate cause is that neither of the two greenlets from
        # the background thread are actually being destroyed, even
        # though the GC is in fact visiting both objects. It's not
        # clear where that leak is? For some reason the thread-local
        # dict holding it isn't being cleaned up.
        #
        # The leak, I think, is in the CPYthon internal function that
        # calls into green_switch(). The argument tuple is still on
        # the C stack somewhere and can't be reached? That doesn't
        # make sense, because the tuple should be collectable when
        # this object goes away.
        #
        # Note that this test sometimes spuriously passes on Linux,
        # for some reason, but I've never seen it pass on macOS.
        self._check_issue251(manually_collect_background=False)

    @fails_leakcheck
    def test_issue251_issue252_need_to_collect_in_background_cleanup_disabled(self):
        self.expect_greenlet_leak = True
        greenlet._greenlet.enable_optional_cleanup(False)
        try:
            self._check_issue251(manually_collect_background=False)
        finally:
            greenlet._greenlet.enable_optional_cleanup(True)

    @fails_leakcheck
    def test_issue251_issue252_explicit_reference_not_collectable(self):
        self._check_issue251(
            manually_collect_background=False,
            explicit_reference_to_switch=True)

    UNTRACK_ATTEMPTS = 100

    def _only_test_some_versions(self):
        # We're only looking for this problem specifically on 3.11,
        # and this set of tests is relatively fragile, depending on
        # OS and memory management details. So we want to run it on 3.11+
        # (obviously) but not every older 3.x version in order to reduce
        # false negatives.
        if sys.version_info[0] >= 3 and sys.version_info[:2] < (3, 8):
            self.skipTest('Only observed on 3.11')

    @ignores_leakcheck
    # Because we're just trying to track raw memory, not objects, and running
    # the leakcheck makes an already slow test slower.
    def test_untracked_memory_doesnt_increase(self):
        # See https://github.com/gevent/gevent/issues/1924
        # and https://github.com/python-greenlet/greenlet/issues/328
        self._only_test_some_versions()
        def f():
            return 1

        ITER = 10000
        def run_it():
            for _ in range(ITER):
                greenlet.greenlet(f).switch()

        # Establish baseline
        for _ in range(3):
            run_it()

        # uss: (Linux, macOS, Windows): aka "Unique Set Size", this is
        # the memory which is unique to a process and which would be
        # freed if the process was terminated right now.
        uss_before = psutil.Process().memory_full_info().uss

        for count in range(self.UNTRACK_ATTEMPTS):
            uss_before = max(uss_before, psutil.Process().memory_full_info().uss)
            run_it()

            uss_after = psutil.Process().memory_full_info().uss
            if uss_after <= uss_before and count > 1:
                break

        self.assertLessEqual(uss_after, uss_before)

    def _check_untracked_memory_thread(self, deallocate_in_thread=True):
        self._only_test_some_versions()
        # Like the above test, but what if there are a bunch of
        # unfinished greenlets in a thread that dies?
        # Does it matter if we deallocate in the thread or not?
        EXIT_COUNT = [0]

        def f():
            try:
                greenlet.getcurrent().parent.switch()
            except greenlet.GreenletExit:
                EXIT_COUNT[0] += 1
                raise
            return 1

        ITER = 10000
        def run_it():
            glets = []
            for _ in range(ITER):
                # Greenlet starts, switches back to us.
                # We keep a strong reference to the greenlet though so it doesn't
                # get a GreenletExit exception.
                g = greenlet.greenlet(f)
                glets.append(g)
                g.switch()

            return glets

        test = self

        class ThreadFunc:
            uss_before = uss_after = 0
            glets = ()
            ITER = 2
            def __call__(self):
                self.uss_before = psutil.Process().memory_full_info().uss

                for _ in range(self.ITER):
                    self.glets += tuple(run_it())

                for g in self.glets:
                    test.assertIn('suspended active', str(g))
                # Drop them.
                if deallocate_in_thread:
                    self.glets = ()
                self.uss_after = psutil.Process().memory_full_info().uss

        # Establish baseline
        uss_before = uss_after = None
        for count in range(self.UNTRACK_ATTEMPTS):
            EXIT_COUNT[0] = 0
            thread_func = ThreadFunc()
            t = threading.Thread(target=thread_func)
            t.start()
            t.join(30)
            self.assertFalse(t.is_alive())

            if uss_before is None:
                uss_before = thread_func.uss_before

            uss_before = max(uss_before, thread_func.uss_before)
            if deallocate_in_thread:
                self.assertEqual(thread_func.glets, ())
                self.assertEqual(EXIT_COUNT[0], ITER * thread_func.ITER)

            del thread_func # Deallocate the greenlets; but this won't raise into them
            del t
            if not deallocate_in_thread:
                self.assertEqual(EXIT_COUNT[0], 0)
            if deallocate_in_thread:
                self.wait_for_pending_cleanups()

            uss_after = psutil.Process().memory_full_info().uss
            # See if we achieve a non-growth state at some point. Break when we do.
            if uss_after <= uss_before and count > 1:
                break

        self.wait_for_pending_cleanups()
        uss_after = psutil.Process().memory_full_info().uss
        self.assertLessEqual(uss_after, uss_before, "after attempts %d" % (count,))

    @ignores_leakcheck
    # Because we're just trying to track raw memory, not objects, and running
    # the leakcheck makes an already slow test slower.
    def test_untracked_memory_doesnt_increase_unfinished_thread_dealloc_in_thread(self):
        self._check_untracked_memory_thread(deallocate_in_thread=True)

    @ignores_leakcheck
    # Because the main greenlets from the background threads do not exit in a timely fashion,
    # we fail the object-based leakchecks.
    def test_untracked_memory_doesnt_increase_unfinished_thread_dealloc_in_main(self):
        self._check_untracked_memory_thread(deallocate_in_thread=False)

if __name__ == '__main__':
    __import__('unittest').main()