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Change FnApiDoFnRunner to skip trySplit checkpoint requests if not draining and nothing has yet been claimed by the tracker. #32044

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merged 4 commits into from
Aug 14, 2024
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Change FnApiDoFnRunner to skip trySplit checkpoint requests if not draining and nothing has yet been claimed by the tracker. #32044

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20dc4dc
Change FnApiDoFnRunner to skip trySplit checkpoint requests if not dr…
scwhittle Jul 29, 2024
36c6e05
address comments
scwhittle Aug 12, 2024
d474fa7
spotless
scwhittle Aug 13, 2024
1b73a0e
Split to residual when no claim is performed in processElement
scwhittle Aug 13, 2024
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40 changes: 37 additions & 3 deletions sdks/java/harness/src/main/java/org/apache/beam/fn/harness/FnApiDoFnRunner.java
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Original file line number Diff line number Diff line change
Expand Up @@ -34,6 +34,7 @@
import java.util.Map;
import java.util.NavigableSet;
import java.util.Set;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.function.BiConsumer;
import java.util.function.BiFunction;
import java.util.function.Consumer;
Expand Down Expand Up @@ -327,6 +328,11 @@ static class Factory<InputT, RestrictionT, PositionT, WatermarkEstimatorStateT,
* otherwise.
*/
private RestrictionTracker<RestrictionT, PositionT> currentTracker;
/**
* If non-null, set to true after currentTracker has had a tryClaim issued on it. Used to ignore
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If it can be null, mark @Nullable and document the meaning of a null value. (it looks to me like it is just "in between calls or during calls where it is not used" but it is hard to ascertain design intent of this class TBH)

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Done, I was being consistent with existing currentTracker but agree it is confusing and me might as well improve it a little.

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Totally makes sense. I might do a pass on this file to narrow the scope of the suppressions. It seems like an important file to leave vulnerable. Thanks!

* checkpoint split requests if no progress was made.
*/
private AtomicBoolean currentTrackerClaimed;

/**
* Only valid during {@link #processTimer} and {@link #processOnWindowExpiration}, null otherwise.
Expand Down Expand Up @@ -877,12 +883,15 @@ private void processElementForSplitRestriction(
currentElement = elem.withValue(elem.getValue().getKey());
currentRestriction = elem.getValue().getValue().getKey();
currentWatermarkEstimatorState = elem.getValue().getValue().getValue();
currentTrackerClaimed = new AtomicBoolean(false);
currentTracker =
RestrictionTrackers.observe(
doFnInvoker.invokeNewTracker(processContext),
new ClaimObserver<PositionT>() {
@Override
public void onClaimed(PositionT position) {}
public void onClaimed(PositionT position) {
currentTrackerClaimed.lazySet(true);
}

@Override
public void onClaimFailed(PositionT position) {}
Expand All @@ -894,6 +903,7 @@ public void onClaimFailed(PositionT position) {}
currentRestriction = null;
currentWatermarkEstimatorState = null;
currentTracker = null;
currentTrackerClaimed = null;
}

this.stateAccessor.finalizeState();
Expand All @@ -909,12 +919,15 @@ private void processElementForWindowObservingSplitRestriction(
(Iterator<BoundedWindow>) elem.getWindows().iterator();
while (windowIterator.hasNext()) {
currentWindow = windowIterator.next();
currentTrackerClaimed = new AtomicBoolean(false);
currentTracker =
RestrictionTrackers.observe(
doFnInvoker.invokeNewTracker(processContext),
new ClaimObserver<PositionT>() {
@Override
public void onClaimed(PositionT position) {}
public void onClaimed(PositionT position) {
currentTrackerClaimed.lazySet(true);
}

@Override
public void onClaimFailed(PositionT position) {}
Expand All @@ -927,6 +940,7 @@ public void onClaimFailed(PositionT position) {}
currentWatermarkEstimatorState = null;
currentWindow = null;
currentTracker = null;
currentTrackerClaimed = null;
}

this.stateAccessor.finalizeState();
Expand All @@ -937,6 +951,8 @@ private void processElementForTruncateRestriction(
currentElement = elem.withValue(elem.getValue().getKey().getKey());
currentRestriction = elem.getValue().getKey().getValue().getKey();
currentWatermarkEstimatorState = elem.getValue().getKey().getValue().getValue();
// For truncation, we don't set currentTrackerClaimed so that we enable checkpointing even if no
// progress is made.
currentTracker =
RestrictionTrackers.observe(
doFnInvoker.invokeNewTracker(processContext),
Expand Down Expand Up @@ -989,6 +1005,8 @@ private void processElementForWindowObservingTruncateRestriction(
currentRestriction = elem.getValue().getKey().getValue().getKey();
currentWatermarkEstimatorState = elem.getValue().getKey().getValue().getValue();
currentWindow = currentWindows.get(windowCurrentIndex);
// We leave currentTrackerClaimed unset as we want to split regardless of if tryClaim is
// called.
currentTracker =
RestrictionTrackers.observe(
doFnInvoker.invokeNewTracker(processContext),
Expand Down Expand Up @@ -1081,12 +1099,15 @@ private void processElementForWindowObservingSizedElementAndRestriction(
currentRestriction = elem.getValue().getKey().getValue().getKey();
currentWatermarkEstimatorState = elem.getValue().getKey().getValue().getValue();
currentWindow = currentWindows.get(windowCurrentIndex);
currentTrackerClaimed = new AtomicBoolean(false);
currentTracker =
RestrictionTrackers.observe(
doFnInvoker.invokeNewTracker(processContext),
new ClaimObserver<PositionT>() {
@Override
public void onClaimed(PositionT position) {}
public void onClaimed(PositionT position) {
currentTrackerClaimed.lazySet(true);
}

@Override
public void onClaimFailed(PositionT position) {}
Expand Down Expand Up @@ -1278,6 +1299,13 @@ private HandlesSplits.SplitResult trySplitForWindowObservingTruncateRestriction(
if (currentWindow == null) {
return null;
}
// We are requesting a checkpoint but have not yet progressed on the restriction, skip
// request.
if (fractionOfRemainder == 0
&& currentTrackerClaimed != null
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Given it is not marked volatile those could be out of date, right? Based on this and your use of lazySet that seems to align with your intent, but I don't have a holistic understanding of this code.

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I think that the setting of the atomicboolean object being consulted is protected by splitLock happensafter ordering. This is the same as currentTracker synchronization.

AtomicBoolean is used since the restriction tracker observing can happen in the background but the laziness is ok since the split would be retried and the real value should be eventually observed.

&& !currentTrackerClaimed.get()) {
return null;
}

SplitResultsWithStopIndex splitResult =
computeSplitForProcessOrTruncate(
Expand Down Expand Up @@ -1628,6 +1656,12 @@ private HandlesSplits.SplitResult trySplitForElementAndRestriction(
if (currentTracker == null) {
return null;
}
// The tracker has not yet been claimed meaning that a checkpoint won't meaningfully advance.
if (fractionOfRemainder == 0
&& currentTrackerClaimed != null
&& !currentTrackerClaimed.get()) {
return null;
}
// Make sure to get the output watermark before we split to ensure that the lower bound
// applies to the residual.
watermarkAndState = currentWatermarkEstimator.getWatermarkAndState();
Expand Down
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