test_lru_cache.py

# Copyright 2022, Optimizely
# 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
#
# https://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 __future__ import annotations
import time
from unittest import TestCase
from optimizely.odp.lru_cache import LRUCache, OptimizelySegmentsCache


class LRUCacheTest(TestCase):
    def test_min_config(self):
        cache = LRUCache(1000, 2000)
        self.assertEqual(1000, cache.capacity)
        self.assertEqual(2000, cache.timeout)

        cache = LRUCache(0, 0)
        self.assertEqual(0, cache.capacity)
        self.assertEqual(0, cache.timeout)

    def test_save_and_lookup(self):
        max_size = 2
        cache = LRUCache(max_size, 1000)

        self.assertIsNone(cache.peek(1))
        cache.save(1, 100)                       # [1]
        cache.save(2, 200)                       # [1, 2]
        cache.save(3, 300)                       # [2, 3]
        self.assertIsNone(cache.peek(1))
        self.assertEqual(200, cache.peek(2))
        self.assertEqual(300, cache.peek(3))

        cache.save(2, 201)                       # [3, 2]
        cache.save(1, 101)                       # [2, 1]
        self.assertEqual(101, cache.peek(1))
        self.assertEqual(201, cache.peek(2))
        self.assertIsNone(cache.peek(3))

        self.assertIsNone(cache.lookup(3))       # [2, 1]
        self.assertEqual(201, cache.lookup(2))   # [1, 2]
        cache.save(3, 302)                       # [2, 3]
        self.assertIsNone(cache.peek(1))
        self.assertEqual(201, cache.peek(2))
        self.assertEqual(302, cache.peek(3))

        self.assertEqual(302, cache.lookup(3))   # [2, 3]
        cache.save(1, 103)                       # [3, 1]
        self.assertEqual(103, cache.peek(1))
        self.assertIsNone(cache.peek(2))
        self.assertEqual(302, cache.peek(3))

        self.assertEqual(len(cache.map), max_size)
        self.assertEqual(len(cache.map), cache.capacity)

    def test_size_zero(self):
        cache = LRUCache(0, 1000)

        self.assertIsNone(cache.lookup(1))
        cache.save(1, 100)                       # [1]
        self.assertIsNone(cache.lookup(1))

    def test_size_less_than_zero(self):
        cache = LRUCache(-2, 1000)

        self.assertIsNone(cache.lookup(1))
        cache.save(1, 100)                       # [1]
        self.assertIsNone(cache.lookup(1))

    def test_timeout(self):
        max_timeout = .5

        cache = LRUCache(1000, max_timeout)

        cache.save(1, 100)                       # [1]
        cache.save(2, 200)                       # [1, 2]
        cache.save(3, 300)                       # [1, 2, 3]
        time.sleep(1.1)  # wait to expire
        cache.save(4, 400)                       # [1, 2, 3, 4]
        cache.save(1, 101)                       # [2, 3, 4, 1]

        self.assertEqual(101, cache.lookup(1))   # [4, 1]
        self.assertIsNone(cache.lookup(2))
        self.assertIsNone(cache.lookup(3))
        self.assertEqual(400, cache.lookup(4))

    def test_timeout_zero(self):
        max_timeout = 0
        cache = LRUCache(1000, max_timeout)

        cache.save(1, 100)                       # [1]
        cache.save(2, 200)                       # [1, 2]
        time.sleep(1)  # wait to expire

        self.assertEqual(100, cache.lookup(1), "should not expire when timeout is 0")
        self.assertEqual(200, cache.lookup(2))

    def test_timeout_less_than_zero(self):
        max_timeout = -2
        cache = LRUCache(1000, max_timeout)

        cache.save(1, 100)                       # [1]
        cache.save(2, 200)                       # [1, 2]
        time.sleep(1)  # wait to expire

        self.assertEqual(100, cache.lookup(1), "should not expire when timeout is less than 0")
        self.assertEqual(200, cache.lookup(2))

    def test_reset(self):
        cache = LRUCache(1000, 600)
        cache.save('wow', 'great')
        cache.save('tow', 'freight')

        self.assertEqual(cache.lookup('wow'), 'great')
        self.assertEqual(len(cache.map), 2)

        cache.reset()

        self.assertEqual(cache.lookup('wow'), None)
        self.assertEqual(len(cache.map), 0)

        cache.save('cow', 'crate')
        self.assertEqual(cache.lookup('cow'), 'crate')

    def test_remove_non_existent_key(self):
        cache = LRUCache(3, 1000)
        cache.save("1", 100)
        cache.save("2", 200)

        cache.remove("3")  # Doesn't exist

        self.assertEqual(cache.lookup("1"), 100)
        self.assertEqual(cache.lookup("2"), 200)

    def test_remove_existing_key(self):
        cache = LRUCache(3, 1000)

        cache.save("1", 100)
        cache.save("2", 200)
        cache.save("3", 300)

        self.assertEqual(cache.lookup("1"), 100)
        self.assertEqual(cache.lookup("2"), 200)
        self.assertEqual(cache.lookup("3"), 300)

        cache.remove("2")

        self.assertEqual(cache.lookup("1"), 100)
        self.assertIsNone(cache.lookup("2"))
        self.assertEqual(cache.lookup("3"), 300)

    def test_remove_from_zero_sized_cache(self):
        cache = LRUCache(0, 1000)
        cache.save("1", 100)
        cache.remove("1")

        self.assertIsNone(cache.lookup("1"))

    def test_remove_and_add_back(self):
        cache = LRUCache(3, 1000)
        cache.save("1", 100)
        cache.save("2", 200)
        cache.save("3", 300)

        cache.remove("2")
        cache.save("2", 201)

        self.assertEqual(cache.lookup("1"), 100)
        self.assertEqual(cache.lookup("2"), 201)
        self.assertEqual(cache.lookup("3"), 300)

    def test_thread_safety(self):
        import threading

        max_size = 100
        cache = LRUCache(max_size, 1000)

        for i in range(1, max_size + 1):
            cache.save(str(i), i * 100)

        def remove_key(k):
            cache.remove(str(k))

        threads = []
        for i in range(1, (max_size // 2) + 1):
            thread = threading.Thread(target=remove_key, args=(i,))
            threads.append(thread)
            thread.start()

        for thread in threads:
            thread.join()

        for i in range(1, max_size + 1):
            if i <= max_size // 2:
                self.assertIsNone(cache.lookup(str(i)))
            else:
                self.assertEqual(cache.lookup(str(i)), i * 100)

        self.assertEqual(len(cache.map), max_size // 2)

    # type checker test
    # confirm that LRUCache matches OptimizelySegmentsCache protocol
    _: OptimizelySegmentsCache = LRUCache(0, 0)