summary refs log tree commit diff
path: root/tests/util/test_linearizer.py
blob: c2a209e637cd490d9febf22c6ead3b29fd395ca9 (plain) (blame)
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
# Copyright 2016 OpenMarket Ltd
# Copyright 2018 New Vector Ltd
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

from typing import Callable, Hashable, Tuple

from twisted.internet import defer, reactor
from twisted.internet.base import ReactorBase
from twisted.internet.defer import CancelledError, Deferred

from synapse.logging.context import LoggingContext, current_context
from synapse.util.async_helpers import Linearizer

from tests import unittest


class LinearizerTestCase(unittest.TestCase):
    def _start_task(
        self, linearizer: Linearizer, key: Hashable
    ) -> Tuple["Deferred[None]", "Deferred[None]", Callable[[], None]]:
        """Starts a task which acquires the linearizer lock, blocks, then completes.

        Args:
            linearizer: The `Linearizer`.
            key: The `Linearizer` key.

        Returns:
            A tuple containing:
             * A cancellable `Deferred` for the entire task.
             * A `Deferred` that resolves once the task acquires the lock.
             * A function that unblocks the task. Must be called by the caller
               to allow the task to release the lock and complete.
        """
        acquired_d: "Deferred[None]" = Deferred()
        unblock_d: "Deferred[None]" = Deferred()

        async def task() -> None:
            async with linearizer.queue(key):
                acquired_d.callback(None)
                await unblock_d

        d = defer.ensureDeferred(task())

        def unblock() -> None:
            unblock_d.callback(None)
            # The next task, if it exists, will acquire the lock and require a kick of
            # the reactor to advance.
            self._pump()

        return d, acquired_d, unblock

    def _pump(self) -> None:
        """Pump the reactor to advance `Linearizer`s."""
        assert isinstance(reactor, ReactorBase)
        while reactor.getDelayedCalls():
            reactor.runUntilCurrent()

    def test_linearizer(self) -> None:
        """Tests that a task is queued up behind an earlier task."""
        linearizer = Linearizer()

        key = object()

        _, acquired_d1, unblock1 = self._start_task(linearizer, key)
        self.assertTrue(acquired_d1.called)

        _, acquired_d2, unblock2 = self._start_task(linearizer, key)
        self.assertFalse(acquired_d2.called)

        # Once the first task is done, the second task can continue.
        unblock1()
        self.assertTrue(acquired_d2.called)

        unblock2()

    def test_linearizer_is_queued(self) -> None:
        """Tests `Linearizer.is_queued`.

        Runs through the same scenario as `test_linearizer`.
        """
        linearizer = Linearizer()

        key = object()

        _, acquired_d1, unblock1 = self._start_task(linearizer, key)
        self.assertTrue(acquired_d1.called)

        # Since the first task acquires the lock immediately, "is_queued" should return
        # false.
        self.assertFalse(linearizer.is_queued(key))

        _, acquired_d2, unblock2 = self._start_task(linearizer, key)
        self.assertFalse(acquired_d2.called)

        # Now the second task is queued up behind the first.
        self.assertTrue(linearizer.is_queued(key))

        unblock1()

        # And now the second task acquires the lock and nothing is in the queue again.
        self.assertTrue(acquired_d2.called)
        self.assertFalse(linearizer.is_queued(key))

        unblock2()
        self.assertFalse(linearizer.is_queued(key))

    def test_lots_of_queued_things(self) -> None:
        """Tests lots of fast things queued up behind a slow thing.

        The stack should *not* explode when the slow thing completes.
        """
        linearizer = Linearizer()
        key = ""

        async def func(i: int) -> None:
            with LoggingContext("func(%s)" % i) as lc:
                async with linearizer.queue(key):
                    self.assertEqual(current_context(), lc)

                self.assertEqual(current_context(), lc)

        _, _, unblock = self._start_task(linearizer, key)
        for i in range(1, 100):
            defer.ensureDeferred(func(i))

        d = defer.ensureDeferred(func(1000))
        unblock()
        self.successResultOf(d)

    def test_multiple_entries(self) -> None:
        """Tests a `Linearizer` with a concurrency above 1."""
        limiter = Linearizer(max_count=3)

        key = object()

        _, acquired_d1, unblock1 = self._start_task(limiter, key)
        self.assertTrue(acquired_d1.called)

        _, acquired_d2, unblock2 = self._start_task(limiter, key)
        self.assertTrue(acquired_d2.called)

        _, acquired_d3, unblock3 = self._start_task(limiter, key)
        self.assertTrue(acquired_d3.called)

        # These next two tasks have to wait.
        _, acquired_d4, unblock4 = self._start_task(limiter, key)
        self.assertFalse(acquired_d4.called)

        _, acquired_d5, unblock5 = self._start_task(limiter, key)
        self.assertFalse(acquired_d5.called)

        # Once the first task completes, the fourth task can continue.
        unblock1()
        self.assertTrue(acquired_d4.called)
        self.assertFalse(acquired_d5.called)

        # Once the third task completes, the fifth task can continue.
        unblock3()
        self.assertTrue(acquired_d5.called)

        # Make all tasks finish.
        unblock2()
        unblock4()
        unblock5()

        # The next task shouldn't have to wait.
        _, acquired_d6, unblock6 = self._start_task(limiter, key)
        self.assertTrue(acquired_d6)
        unblock6()

    def test_cancellation(self) -> None:
        """Tests cancellation while waiting for a `Linearizer`."""
        linearizer = Linearizer()

        key = object()

        d1, acquired_d1, unblock1 = self._start_task(linearizer, key)
        self.assertTrue(acquired_d1.called)

        # Create a second task, waiting for the first task.
        d2, acquired_d2, _ = self._start_task(linearizer, key)
        self.assertFalse(acquired_d2.called)

        # Create a third task, waiting for the second task.
        d3, acquired_d3, unblock3 = self._start_task(linearizer, key)
        self.assertFalse(acquired_d3.called)

        # Cancel the waiting second task.
        d2.cancel()

        unblock1()
        self.successResultOf(d1)

        self.assertTrue(d2.called)
        self.failureResultOf(d2, CancelledError)

        # The third task should continue running.
        self.assertTrue(
            acquired_d3.called,
            "Third task did not get the lock after the second task was cancelled",
        )
        unblock3()
        self.successResultOf(d3)