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feat: improve wait logic to a more elegant solution open-feature#1160
Signed-off-by: christian.lutnik <[email protected]>
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39 changes: 0 additions & 39 deletions
39
...ers/flagd/src/main/java/dev/openfeature/contrib/providers/flagd/resolver/common/Util.java
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72 changes: 72 additions & 0 deletions
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...ers/flagd/src/main/java/dev/openfeature/contrib/providers/flagd/resolver/common/Wait.java
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,72 @@ | ||
| package dev.openfeature.contrib.providers.flagd.resolver.common; | ||
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| import dev.openfeature.sdk.exceptions.GeneralError; | ||
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| /** | ||
| * A helper class to wait for events. | ||
| */ | ||
| public class Wait { | ||
| private volatile boolean isFinished; | ||
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| /** | ||
| * Create a new Wait object. | ||
| */ | ||
| public Wait() {} | ||
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| private Wait(boolean isFinished) { | ||
| this.isFinished = isFinished; | ||
| } | ||
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| /** | ||
| * Blocks the calling thread until either {@link Wait#onFinished()} is called or the deadline is exceeded, whatever | ||
| * happens first. | ||
| * If the deadline is exceeded, a GeneralError will be thrown. | ||
| * | ||
| * @param deadline the maximum time in ms to wait | ||
| * @throws GeneralError when the deadline is exceeded before {@link Wait#onFinished()} is called on this object | ||
| */ | ||
| public void waitUntilFinished(long deadline) { | ||
| long start = System.currentTimeMillis(); | ||
| long end = start + deadline; | ||
| while (!isFinished) { | ||
| long now = System.currentTimeMillis(); | ||
| // if wait(0) is called, the thread would wait forever, so we abort when this would happen | ||
| if (now >= end) { | ||
| throw new GeneralError(String.format( | ||
| "Deadline exceeded. Condition did not complete within the %d ms deadline", deadline)); | ||
| } | ||
| long remaining = end - now; | ||
| synchronized (this) { | ||
| if (isFinished) { // might have changed in the meantime | ||
| return; | ||
| } | ||
| try { | ||
| this.wait(remaining); | ||
| } catch (InterruptedException e) { | ||
| // try again. Leave the continue to make PMD happy | ||
| continue; | ||
| } | ||
| } | ||
| } | ||
| } | ||
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| /** | ||
| * Wake up all threads that have called {@link Wait#waitUntilFinished(long)}. | ||
| */ | ||
| public void onFinished() { | ||
| synchronized (this) { | ||
| isFinished = true; | ||
| this.notifyAll(); | ||
| } | ||
| } | ||
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| /** | ||
| * Create a new Wait object that is already finished. Calls to {@link Wait#waitUntilFinished(long)} will return | ||
| * immediately. | ||
| * | ||
| * @return an already finished Wait object | ||
| */ | ||
| public static Wait finished() { | ||
| return new Wait(true); | ||
| } | ||
| } |
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111
...flagd/src/test/java/dev/openfeature/contrib/providers/flagd/resolver/common/WaitTest.java
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,111 @@ | ||
| package dev.openfeature.contrib.providers.flagd.resolver.common; | ||
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| import dev.openfeature.sdk.exceptions.GeneralError; | ||
| import java.util.concurrent.atomic.AtomicBoolean; | ||
| import java.util.concurrent.atomic.AtomicLong; | ||
| import org.junit.jupiter.api.Assertions; | ||
| import org.junit.jupiter.api.Test; | ||
| import org.junit.jupiter.api.Timeout; | ||
|
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| class WaitTest { | ||
| private static final long PERMISSIBLE_EPSILON = 20; | ||
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| @Timeout(2) | ||
| @Test | ||
| void waitUntilFinished_failsWhenDeadlineElapses() { | ||
| final Wait wait = new Wait(); | ||
| Assertions.assertThrows(GeneralError.class, () -> wait.waitUntilFinished(10)); | ||
| } | ||
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| @Timeout(2) | ||
| @Test | ||
| void waitUntilFinished_WaitsApproxForDeadline() { | ||
| final Wait wait = new Wait(); | ||
| final AtomicLong start = new AtomicLong(); | ||
| final AtomicLong end = new AtomicLong(); | ||
| final long deadline = 45; | ||
| Assertions.assertThrows(GeneralError.class, () -> { | ||
| start.set(System.currentTimeMillis()); | ||
| try { | ||
| wait.waitUntilFinished(deadline); | ||
| } catch (Exception e) { | ||
| end.set(System.currentTimeMillis()); | ||
| throw e; | ||
| } | ||
| }); | ||
| final long elapsed = end.get() - start.get(); | ||
| // should wait at least for the deadline | ||
| Assertions.assertTrue(elapsed >= deadline); | ||
| // should not wait much longer than the deadline | ||
| Assertions.assertTrue(elapsed < deadline + PERMISSIBLE_EPSILON); | ||
| } | ||
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| @Timeout(2) | ||
| @Test | ||
| void interruptingWaitingThread_isIgnored() throws InterruptedException { | ||
| final AtomicBoolean isWaiting = new AtomicBoolean(); | ||
| final Wait wait = new Wait(); | ||
| final long deadline = 500; | ||
| Thread t0 = new Thread(() -> { | ||
| long start = System.currentTimeMillis(); | ||
| isWaiting.set(true); | ||
| wait.waitUntilFinished(deadline); | ||
| long end = System.currentTimeMillis(); | ||
| long duration = end - start; | ||
| // even though thread was interrupted, it still waited for the deadline | ||
| Assertions.assertTrue(duration >= deadline); | ||
| Assertions.assertTrue(duration < deadline + PERMISSIBLE_EPSILON); | ||
| }); | ||
| t0.start(); | ||
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| while (!isWaiting.get()) { | ||
| Thread.yield(); | ||
| } | ||
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| Thread.sleep(10); // t0 should have started waiting in the meantime | ||
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| for (int i = 0; i < 50; i++) { | ||
| t0.interrupt(); | ||
| Thread.sleep(10); | ||
| } | ||
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| t0.join(); | ||
| } | ||
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| @Timeout(2) | ||
| @Test | ||
| void callingOnFinished_wakesUpWaitingThread() throws InterruptedException { | ||
| final AtomicBoolean isWaiting = new AtomicBoolean(); | ||
| final Wait wait = new Wait(); | ||
| Thread t0 = new Thread(() -> { | ||
| long start = System.currentTimeMillis(); | ||
| isWaiting.set(true); | ||
| wait.waitUntilFinished(10000); | ||
| long end = System.currentTimeMillis(); | ||
| long duration = end - start; | ||
| Assertions.assertTrue(duration < PERMISSIBLE_EPSILON); | ||
| }); | ||
| t0.start(); | ||
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| while (!isWaiting.get()) { | ||
| Thread.yield(); | ||
| } | ||
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| Thread.sleep(10); // t0 should have started waiting in the meantime | ||
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| wait.onFinished(); | ||
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| t0.join(); | ||
| } | ||
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| @Timeout(2) | ||
| @Test | ||
| void waitingOnFinished_returnsInstantly() { | ||
| Wait finished = Wait.finished(); | ||
| long start = System.currentTimeMillis(); | ||
| finished.waitUntilFinished(10000); | ||
| long end = System.currentTimeMillis(); | ||
| // do not use PERMISSIBLE_EPSILON here, this should happen faster than that | ||
| Assertions.assertTrue(start + 2 > end); | ||
| } | ||
| } |
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