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fix(common): publish queue configuration safely #7141

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Merged
Aias00 merged 4 commits into from
Sep 21, 2026
Merged

fix(common): publish queue configuration safely #7141

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661c6c1
fix(common): publish queue configuration safely
dengliming Sep 20, 2026
1ba576a
Merge branch 'master' into fix-6774-memory-safe-queue-visibility
Aias00 Sep 21, 2026
72648aa
Merge branch 'master' into fix-6774-memory-safe-queue-visibility
Aias00 Sep 21, 2026
2bdbb4f
Merge branch 'master' into fix-6774-memory-safe-queue-visibility
Aias00 Sep 21, 2026
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4 changes: 2 additions & 2 deletions ...mmon/src/main/java/org/apache/shenyu/common/concurrent/MemorySafeLinkedBlockingQueue.java
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Original file line number Diff line number Diff line change
Expand Up @@ -30,9 +30,9 @@ public class MemorySafeLinkedBlockingQueue<E> extends LinkedBlockingQueue<E> {

private static final long serialVersionUID = 8032578371749960142L;

private int maxFreeMemory;
private volatile int maxFreeMemory;

@Aias00 Aias00 Sep 21, 2026

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volatile is the right fix and it is genuinely needed here - unlike a plain immutable field, both values have public setters (setMaxFreeMemory / setRejector), so they really are mutable shared state read from put/offer on arbitrary threads.

Two notes, neither blocking:

  1. hasRemainedMemory() is still check-then-act:
if (!hasRemainedMemory()) { rejector.reject(e, this); return false; }
return super.offer(e);

volatile gives visibility for maxFreeMemory/rejector, it does not make the memory check atomic with the enqueue. That is fine for a best-effort OOM guard - arguably publishing the config safely is exactly what was missing - but worth a comment so nobody reads volatile as "the guard is atomic".

  1. Same as elsewhere in this batch: asserting Modifier.isVolatile(...) by reflection checks an implementation detail, and would silently pass even if the setter were removed and the field became effectively final. A behavioural test (e.g. setMaxFreeMemory(0) from one thread while another offers) is more valuable, though harder to make deterministic - so keeping this as a cheap regression guard is acceptable.


private Rejector<E> rejector;
private volatile Rejector<E> rejector;

public MemorySafeLinkedBlockingQueue(final int maxFreeMemory) {
super(Integer.MAX_VALUE);
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13 changes: 13 additions & 0 deletions .../src/test/java/org/apache/shenyu/common/concurrent/MemorySafeLinkedBlockingQueueTest.java
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Expand Up @@ -19,9 +19,13 @@

import org.junit.jupiter.api.Test;

import java.lang.reflect.Field;
import java.lang.reflect.Modifier;

import static org.hamcrest.MatcherAssert.assertThat;
import static org.hamcrest.Matchers.is;
import static org.junit.jupiter.api.Assertions.assertThrows;
import static org.junit.jupiter.api.Assertions.assertTrue;

public class MemorySafeLinkedBlockingQueueTest {
@Test
Expand All @@ -44,4 +48,13 @@ public void testCustomReject() throws Exception {
assertThrows(RejectException.class, () -> queue.offer(() -> {
}));
}

@Test
public void testMutableConfigurationIsVolatile() throws NoSuchFieldException {
Field maxFreeMemory = MemorySafeLinkedBlockingQueue.class.getDeclaredField("maxFreeMemory");
Field rejector = MemorySafeLinkedBlockingQueue.class.getDeclaredField("rejector");

assertTrue(Modifier.isVolatile(maxFreeMemory.getModifiers()));
assertTrue(Modifier.isVolatile(rejector.getModifiers()));
}
}
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