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Fix EvictableCacheBuilder#expireAfterWrite behavior #14476

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atanasenko wants to merge 1 commit into from
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Fix EvictableCacheBuilder#expireAfterWrite behavior #14476

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15 changes: 12 additions & 3 deletions lib/trino-collect/src/main/java/io/trino/collect/cache/EvictableCache.java
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Original file line number Diff line number Diff line change
Expand Up @@ -77,7 +77,7 @@ class EvictableCache<K, V>
tokens.remove(token.getKey(), token);
}
}),
new TokenCacheLoader<>(cacheLoader));
new TokenCacheLoader<>(cacheLoader, tokens));
}

@SuppressModernizer // CacheBuilder.build(CacheLoader) is forbidden, advising to use this class as a safety-adding wrapper.
Expand All @@ -104,8 +104,13 @@ public V get(K key, Callable<? extends V> valueLoader)
{
Token<K> newToken = new Token<>(key);
Token<K> token = tokens.computeIfAbsent(key, ignored -> newToken);
Callable<? extends V> valueLoaderImpl = () -> {
// revive token if it got expired before reloading
tokens.computeIfAbsent(token.getKey(), ignored -> token);
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@findepi findepi Oct 7, 2022

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would this be equivalent?

Suggested change
tokens.computeIfAbsent(token.getKey(), ignored -> token);
tokens.computeIfAbsent(key, ignored -> token);

return valueLoader.call();
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@findepi findepi Oct 7, 2022

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just thinking -- should the revival happen before or after valueLoader.call?
or it doesn't matter?

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@findepi findepi Oct 7, 2022

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related -- if valueLoader throws and this wasn't a new token, we can revive it and leak

};
try {
return dataCache.get(token, valueLoader);
return dataCache.get(token, valueLoaderImpl);
}
catch (Throwable e) {
if (newToken == token) {
Expand Down Expand Up @@ -394,16 +399,20 @@ private static class TokenCacheLoader<K, V>
extends CacheLoader<Token<K>, V>
{
private final CacheLoader<? super K, V> delegate;
private final ConcurrentHashMap<K, Token<K>> tokens;

public TokenCacheLoader(CacheLoader<? super K, V> delegate)
public TokenCacheLoader(CacheLoader<? super K, V> delegate, ConcurrentHashMap<K, Token<K>> tokens)
{
this.delegate = requireNonNull(delegate, "delegate is null");
this.tokens = requireNonNull(tokens, "tokens is null");
}

@Override
public V load(Token<K> token)
throws Exception
{
// revive token if it got expired before reloading
tokens.computeIfAbsent(token.getKey(), ignored -> token);
return delegate.load(token.getKey());
}

Expand Down
23 changes: 23 additions & 0 deletions lib/trino-collect/src/test/java/io/trino/collect/cache/TestEvictableCache.java
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Expand Up @@ -23,6 +23,7 @@
import org.testng.annotations.DataProvider;
import org.testng.annotations.Test;

import java.time.Instant;
import java.util.ArrayList;
import java.util.List;
import java.util.Set;
Expand All @@ -43,8 +44,10 @@
import static io.trino.collect.cache.CacheStatsAssertions.assertCacheStats;
import static java.lang.Math.toIntExact;
import static java.lang.String.format;
import static java.time.temporal.ChronoUnit.MILLIS;
import static java.util.concurrent.Executors.newFixedThreadPool;
import static java.util.concurrent.TimeUnit.DAYS;
import static java.util.concurrent.TimeUnit.MILLISECONDS;
import static java.util.concurrent.TimeUnit.SECONDS;
import static org.assertj.core.api.Assertions.assertThat;
import static org.assertj.core.api.Assertions.assertThatThrownBy;
Expand Down Expand Up @@ -108,6 +111,26 @@ public void testEvictByWeight()
assertThat(cache.asMap().values().stream().mapToInt(String::length).sum()).as("values length sum").isLessThanOrEqualTo(20);
}

@Test(timeOut = TEST_TIMEOUT_MILLIS)
public void testLoadOnceWithTimeEviction()
throws Exception
{
int ttl = 50;
int expectedCalls = 10;

AtomicInteger counter = new AtomicInteger();
Cache<String, Integer> cache = EvictableCacheBuilder.newBuilder()
.expireAfterWrite(ttl, MILLISECONDS)
.build();

Instant until = Instant.now().plus(ttl * expectedCalls, MILLIS);
while (until.isAfter(Instant.now())) {
Comment on lines 126 to 127
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@findepi findepi Oct 6, 2022

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Use Stopwatch -- it's ligheter-weight and easier to lead.

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@findepi findepi Oct 6, 2022

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BTW i wanted to put a PR with a test preventing memory leak (#14476 (comment)) and end-up also writing my version of this test #14502. not sure if this helps

cache.get("foo", counter::incrementAndGet);
Thread.sleep(1);
}
assertThat(counter.get()).isEqualTo(expectedCalls);
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@findepi findepi Oct 6, 2022

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the timeout until.isAfter(Instant.now()) condition is checked before a call is made, so we should expect allow one more call here

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@atanasenko atanasenko Oct 6, 2022

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It never goes past the threshold of the last expiration. Or am I missing something?

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@findepi findepi Oct 6, 2022

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You don't know how much time elapses between checking the clock and invoking cache.get

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@findepi findepi Oct 7, 2022

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am i missing something?

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@findepi findepi Oct 14, 2022

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i think this boils down to the fact it's much better to use ~Ticker for tests, per @losipiuk #14502 (comment)

}

@Test(timeOut = TEST_TIMEOUT_MILLIS)
public void testReplace()
throws Exception
Expand Down
26 changes: 26 additions & 0 deletions lib/trino-collect/src/test/java/io/trino/collect/cache/TestEvictableLoadingCache.java
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Expand Up @@ -24,6 +24,7 @@
import org.testng.annotations.DataProvider;
import org.testng.annotations.Test;

import java.time.Instant;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
Expand All @@ -47,7 +48,9 @@
import static io.trino.collect.cache.CacheStatsAssertions.assertCacheStats;
import static java.lang.Math.toIntExact;
import static java.lang.String.format;
import static java.time.temporal.ChronoUnit.MILLIS;
import static java.util.concurrent.Executors.newFixedThreadPool;
import static java.util.concurrent.TimeUnit.MILLISECONDS;
import static java.util.concurrent.TimeUnit.SECONDS;
import static org.assertj.core.api.Assertions.assertThat;
import static org.assertj.core.api.Assertions.assertThatThrownBy;
Expand Down Expand Up @@ -112,6 +115,29 @@ public void testEvictByWeight()
assertThat(cache.asMap().values().stream().mapToInt(String::length).sum()).as("values length sum").isLessThanOrEqualTo(20);
}

@Test(timeOut = TEST_TIMEOUT_MILLIS)
public void testLoadOnceWithTimeEviction()
throws Exception
{
int ttl = 50;
int expectedCalls = 10;

AtomicInteger counter = new AtomicInteger();
LoadingCache<String, String> cache = EvictableCacheBuilder.newBuilder()
.expireAfterWrite(ttl, MILLISECONDS)
.build(CacheLoader.from(k -> {
counter.incrementAndGet();
return k;
}));

Instant until = Instant.now().plus(ttl * expectedCalls, MILLIS);
while (until.isAfter(Instant.now())) {
cache.get("foo");
Thread.sleep(1);
}
assertThat(counter.get()).isEqualTo(expectedCalls);
}

@Test(timeOut = TEST_TIMEOUT_MILLIS, dataProvider = "testDisabledCacheDataProvider")
public void testDisabledCache(String behavior)
throws Exception
Expand Down