8347542: Gatherers.mapConcurrent exhibits undesired behavior under variable delays, interruption, and finishing

[viktorklang-ora]

Backport to jdk24 of https://bugs.openjdk.org/browse/JDK-8347274

---

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Integration blocker

 ⚠️ Issue of type Backport is not allowed for integrations

Issue

• JDK-8347542: Gatherers.mapConcurrent exhibits undesired behavior under variable delays, interruption, and finishing (Backport - P3)

Reviewers

• Alan Bateman (@AlanBateman - Reviewer)

Reviewing

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[mlbridge]

Webrevs

• 00: Full (79a8eb94)

[AlanBateman]

Did you use "/backport" or is this a manual back port?

[viktorklang-ora]

@AlanBateman I did a manual backport since there was a merge conflict (on the copyright notice change).

[He-Pin]

Does this fix the OOM problem?

import java.util.stream.Gatherers;
import java.util.stream.IntStream;

/**
 * TODO: description of this file
 *
 * @author 虎鸣
 */
public class Main {
    public static void main(String[] args) {
        final var stream = IntStream.range(0, Integer.MAX_VALUE);
        stream.boxed()
            .gather(Gatherers.mapConcurrent(
                2,
                i -> {
                    if (i == 0) {
                        try {
                            Thread.sleep(Integer.MAX_VALUE);
                        } catch (InterruptedException e) {
                            throw new RuntimeException(e);
                        }
                    }
                    return i;
                }))
            .forEach(System.out::println);
        try {
            Thread.sleep(Integer.MAX_VALUE);
        } catch (InterruptedException e) {
            throw new RuntimeException(e);
        }
    }
}

[viktorklang-ora]

Opening a new PR as something didn't go right with this manual backport.

[viktorklang-ora]

@He-Pin I believe it will, yes.