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Control max parallelism on a dedicated thread (#875)
Addresses: #867
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63 changes: 63 additions & 0 deletions
63
src/test/java/com/pivovarit/collectors/ExecutorPollutionTest.java
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package com.pivovarit.collectors; | ||
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import org.junit.jupiter.api.DynamicTest; | ||
import org.junit.jupiter.api.TestFactory; | ||
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import java.util.concurrent.CompletableFuture; | ||
import java.util.concurrent.Executor; | ||
import java.util.concurrent.ExecutorService; | ||
import java.util.concurrent.LinkedBlockingQueue; | ||
import java.util.concurrent.ThreadPoolExecutor; | ||
import java.util.concurrent.TimeUnit; | ||
import java.util.function.Function; | ||
import java.util.stream.Collector; | ||
import java.util.stream.Stream; | ||
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import static java.util.stream.Collectors.toList; | ||
import static java.util.stream.Stream.of; | ||
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class ExecutorPollutionTest { | ||
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@TestFactory | ||
Stream<DynamicTest> shouldStartProcessingElementsTests() { | ||
return of( | ||
shouldNotSubmitMoreTasksThanParallelism(ParallelCollectors::parallel, "parallel#1"), | ||
shouldNotSubmitMoreTasksThanParallelism((f, e, p) -> ParallelCollectors.parallel(f, toList(), e, p), "parallel#2"), | ||
shouldNotSubmitMoreTasksThanParallelism(ParallelCollectors::parallelToStream, "parallelToStream"), | ||
shouldNotSubmitMoreTasksThanParallelism(ParallelCollectors::parallelToOrderedStream, "parallelToOrderedStream"), | ||
shouldNotSubmitMoreTasksThanParallelism(ParallelCollectors.Batching::parallel, "parallel#1 (batching)"), | ||
shouldNotSubmitMoreTasksThanParallelism((f, e, p) -> ParallelCollectors.Batching.parallel(f, toList(), e, p), "parallel#2 (batching)"), | ||
shouldNotSubmitMoreTasksThanParallelism(ParallelCollectors.Batching::parallelToStream, "parallelToStream (batching)"), | ||
shouldNotSubmitMoreTasksThanParallelism(ParallelCollectors.Batching::parallelToOrderedStream, "parallelToOrderedStream (batching)") | ||
); | ||
} | ||
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private static DynamicTest shouldNotSubmitMoreTasksThanParallelism(CollectorFactory<Integer> collector, String name) { | ||
return DynamicTest.dynamicTest(name, () -> { | ||
ExecutorService e = warmedUp(new ThreadPoolExecutor(2, 2, 0L, TimeUnit.MILLISECONDS, new LinkedBlockingQueue<>(2))); | ||
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Object result = Stream.generate(() -> 42) | ||
.limit(1000) | ||
.collect(collector.apply(i -> i, e, 2)); | ||
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if (result instanceof CompletableFuture<?>) { | ||
((CompletableFuture<?>) result).join(); | ||
} else if (result instanceof Stream<?>) { | ||
((Stream<?>) result).forEach((__) -> {}); | ||
} else { | ||
throw new IllegalStateException("can't happen"); | ||
} | ||
}); | ||
} | ||
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interface CollectorFactory<T> { | ||
Collector<T, ?, ?> apply(Function<T, ?> function, Executor executorService, int parallelism); | ||
} | ||
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private static ThreadPoolExecutor warmedUp(ThreadPoolExecutor e) { | ||
for (int i = 0; i < e.getCorePoolSize(); i++) { | ||
e.submit(() -> {}); | ||
} | ||
return e; | ||
} | ||
} |