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Allow expired entries to be resurrected (fixes #30)
An expired entry may be replaced in the cache prior to it being evicted by a maintenance cycle. When the maintenace is being performed and reads a stale timestamp, during eviction is must validate that the entry is still an eviction candidate. This was reported to have caused excessive evictions for short time durations, so the race was not benign as originally thought.
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caffeine/src/test/java/com/github/benmanes/caffeine/cache/issues/Issue30Test.java
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| /* | ||
| * Copyright 2015 Ben Manes. All Rights Reserved. | ||
| * | ||
| * 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. | ||
| */ | ||
| package com.github.benmanes.caffeine.cache.issues; | ||
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| import static com.github.benmanes.caffeine.testing.IsFutureValue.futureOf; | ||
| import static org.hamcrest.MatcherAssert.assertThat; | ||
| import static org.hamcrest.Matchers.is; | ||
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| import java.text.SimpleDateFormat; | ||
| import java.util.Date; | ||
| import java.util.concurrent.CompletableFuture; | ||
| import java.util.concurrent.ConcurrentHashMap; | ||
| import java.util.concurrent.ConcurrentMap; | ||
| import java.util.concurrent.ExecutionException; | ||
| import java.util.concurrent.Executor; | ||
| import java.util.concurrent.TimeUnit; | ||
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| import org.testng.annotations.DataProvider; | ||
| import org.testng.annotations.Test; | ||
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| import com.github.benmanes.caffeine.cache.AsyncLoadingCache; | ||
| import com.github.benmanes.caffeine.cache.CacheLoader; | ||
| import com.github.benmanes.caffeine.cache.Caffeine; | ||
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| /** | ||
| * Issue #30: Unexpected cache misses with <tt>expireAfterWrite</tt> using multiple keys. | ||
| * <p> | ||
| * Prior to eviction, the cache must revalidate that the entry has expired. If the entry was updated | ||
| * but the maintenance thread reads a stale value, then the entry may be prematurely expired. The | ||
| * removal must detect that the entry was "resurrected" and cancel the expiration. | ||
| * | ||
| * @author yurgis2 | ||
| * @author [email protected] (Ben Manes) | ||
| */ | ||
| public final class Issue30Test { | ||
| private static final boolean DEBUG = false; | ||
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| private static final String A_KEY = "foo"; | ||
| private static final String A_ORIGINAL = "foo0"; | ||
| private static final String A_UPDATE_1 = "foo1"; | ||
| private static final String A_UPDATE_2 = "foo2"; | ||
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| private static final String B_KEY = "bar"; | ||
| private static final String B_ORIGINAL = "bar0"; | ||
| private static final String B_UPDATE_1 = "bar1"; | ||
| private static final String B_UPDATE_2 = "bar2"; | ||
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| private static final int TTL = 100; | ||
| private static final int EPSILON = 10; | ||
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| @DataProvider(name = "cache") | ||
| public Object[][] providesCache() { | ||
| ConcurrentMap<String, String> source = new ConcurrentHashMap<>(); | ||
| ConcurrentMap<String, Date> lastLoad = new ConcurrentHashMap<>(); | ||
| AsyncLoadingCache<String, String> cache = Caffeine.newBuilder() | ||
| .expireAfterWrite(TTL, TimeUnit.MILLISECONDS) | ||
| .buildAsync(new Loader(source, lastLoad)); | ||
| return new Object[][] {{ cache, source, lastLoad }}; | ||
| } | ||
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| // FIXME: For now, this test has to be run manually due to CI & build having enough shared work | ||
| // to cause the delays to be exceeded. This tests needs to be isolated so that no other machine | ||
| // work causes the timing periods to exceed the thresholds. | ||
| @Test(enabled = false, dataProvider = "cache", invocationCount = 100, threadPoolSize = 10) | ||
| public void expiration(AsyncLoadingCache<String, String> cache, | ||
| ConcurrentMap<String, String> source, ConcurrentMap<String, Date> lastLoad) throws Exception { | ||
| initialValues(cache, source, lastLoad); | ||
| firstUpdate(cache, source); | ||
| secondUpdate(cache, source); | ||
| } | ||
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| private void initialValues(AsyncLoadingCache<String, String> cache, | ||
| ConcurrentMap<String, String> source, ConcurrentMap<String, Date> lastLoad) | ||
| throws InterruptedException, ExecutionException { | ||
| source.put(A_KEY, A_ORIGINAL); | ||
| source.put(B_KEY, B_ORIGINAL); | ||
| lastLoad.clear(); | ||
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| assertThat("should serve initial value", cache.get(A_KEY), is(futureOf(A_ORIGINAL))); | ||
| assertThat("should serve initial value", cache.get(B_KEY), is(futureOf(B_ORIGINAL))); | ||
| } | ||
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| private void firstUpdate(AsyncLoadingCache<String, String> cache, | ||
| ConcurrentMap<String, String> source) throws InterruptedException, ExecutionException { | ||
| source.put(A_KEY, A_UPDATE_1); | ||
| source.put(B_KEY, B_UPDATE_1); | ||
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| assertThat("should serve cached initial value", cache.get(A_KEY), is(futureOf(A_ORIGINAL))); | ||
| assertThat("should serve cached initial value", cache.get(B_KEY), is(futureOf(B_ORIGINAL))); | ||
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| Thread.sleep(EPSILON); // sleep for less than expiration | ||
| assertThat("still serve cached initial value", cache.get(A_KEY), is(futureOf(A_ORIGINAL))); | ||
| assertThat("still serve cached initial value", cache.get(B_KEY), is(futureOf(B_ORIGINAL))); | ||
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| Thread.sleep(TTL + EPSILON); // sleep until expiration | ||
| assertThat("now serve first updated value", cache.get(A_KEY), is(futureOf(A_UPDATE_1))); | ||
| assertThat("now serve first updated value", cache.get(B_KEY), is(futureOf(B_UPDATE_1))); | ||
| } | ||
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| private void secondUpdate(AsyncLoadingCache<String, String> cache, | ||
| ConcurrentMap<String, String> source) throws Exception { | ||
| source.put(A_KEY, A_UPDATE_2); | ||
| source.put(B_KEY, B_UPDATE_2); | ||
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| assertThat("serve cached first updated value", cache.get(A_KEY), is(futureOf(A_UPDATE_1))); | ||
| assertThat("serve cached first updated value", cache.get(B_KEY), is(futureOf(B_UPDATE_1))); | ||
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| Thread.sleep(EPSILON); // sleep for less than expiration | ||
| assertThat("serve cached first updated value", cache.get(A_KEY), is(futureOf(A_UPDATE_1))); | ||
| assertThat("serve cached first updated value", cache.get(A_KEY), is(futureOf(A_UPDATE_1))); | ||
| } | ||
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| static final class Loader implements CacheLoader<String, String> { | ||
| final ConcurrentMap<String, String> source; | ||
| final ConcurrentMap<String, Date> lastLoad; | ||
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| Loader(ConcurrentMap<String, String> source, ConcurrentMap<String, Date> lastLoad) { | ||
| this.source = source; | ||
| this.lastLoad = lastLoad; | ||
| } | ||
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| @Override | ||
| public String load(String key) { | ||
| throw new IllegalStateException(); | ||
| } | ||
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| @Override | ||
| public CompletableFuture<String> asyncLoad(String key, Executor executor) { | ||
| reportCacheMiss(key); | ||
| return CompletableFuture.completedFuture(source.get(key)); | ||
| } | ||
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| private void reportCacheMiss(String key) { | ||
| Date now = new Date(); | ||
| Date last = lastLoad.get(key); | ||
| lastLoad.put(key, now); | ||
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| if (DEBUG) { | ||
| String time = new SimpleDateFormat("hh:MM:ss.SSS").format(new Date()); | ||
| if (last == null) { | ||
| System.out.println(key + ": first load @ " + time); | ||
| } else { | ||
| long duration = (now.getTime() - last.getTime()); | ||
| System.out.println(key + ": " + duration + "ms after last load @ " + time); | ||
| } | ||
| } | ||
| } | ||
| } | ||
| } |