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[BEAM-9308] Decorrelate state cleanup timers #10852

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[BEAM-9308] Decorrelate state cleanup timers #10852

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25 changes: 18 additions & 7 deletions ...flow-java/worker/src/main/java/org/apache/beam/runners/dataflow/worker/SimpleParDoFn.java
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Expand Up @@ -54,6 +54,7 @@
import org.apache.beam.sdk.transforms.windowing.BoundedWindow;
import org.apache.beam.sdk.util.DoFnInfo;
import org.apache.beam.sdk.util.WindowedValue;
import org.apache.beam.sdk.values.KV;
import org.apache.beam.sdk.values.PCollectionView;
import org.apache.beam.sdk.values.TupleTag;
import org.apache.beam.sdk.values.WindowingStrategy;
Expand Down Expand Up @@ -326,9 +327,20 @@ public void processElement(Object untypedElem) throws Exception {
WindowedValue<InputT> elem = (WindowedValue<InputT>) untypedElem;

if (fnSignature != null && fnSignature.stateDeclarations().size() > 0) {
int jitterMs = 0;
if (elem.getValue() instanceof KV<?, ?>) {
int keyHash = ((KV<?, ?>) elem.getValue()).getKey().hashCode();
// mix the hash in case the key has a "bad" hash function (eg Integer just returns itself).
int mixedHash = 0x1b873593 * Integer.rotateLeft(keyHash * 0xcc9e2d51, 15);
// spread the hash across 180 seconds, an arbitrarily chosen number.
// TODO: make this configurable?
jitterMs = Math.abs(mixedHash % 180) * 1000;
}

registerStateCleanup(
(WindowingStrategy<?, BoundedWindow>) getDoFnInfo().getWindowingStrategy(),
(Collection<BoundedWindow>) elem.getWindows());
(Collection<BoundedWindow>) elem.getWindows(),
jitterMs);
}

outputsPerElementTracker.onProcessElement();
Expand Down Expand Up @@ -477,18 +489,17 @@ private void processTimers(
}

private <W extends BoundedWindow> void registerStateCleanup(
WindowingStrategy<?, W> windowingStrategy, Collection<W> windowsToCleanup) {
WindowingStrategy<?, W> windowingStrategy, Collection<W> windowsToCleanup, int jitterMs) {
Coder<W> windowCoder = windowingStrategy.getWindowFn().windowCoder();

for (W window : windowsToCleanup) {
// The stepContext is the thing that know if it is batch or streaming, hence
// whether state needs to be cleaned up or will simply be discarded so the
// timer can be ignored
stepContext.setStateCleanupTimer(
CLEANUP_TIMER_ID,
window,
windowCoder,
earliestAllowableCleanupTime(window, windowingStrategy));
Instant jitteredCleanupTime =
earliestAllowableCleanupTime(window, windowingStrategy).plus(jitterMs);

stepContext.setStateCleanupTimer(CLEANUP_TIMER_ID, window, windowCoder, jitteredCleanupTime);
}
}

Expand Down