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fix: Do not cache futures as they can be cancelled on timeout #26367

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Merged
arhimondr merged 2 commits into from
Oct 23, 2025
+22 −18
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fix: Do not cache futures as they can be cancelled on timeout #26367

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1763bd9
fix: Avoid re-creating future in ScaledWriterScheduler
arhimondr Oct 20, 2025
8a6713b
fix: Do not cache futures as they can be cancelled on timeout
arhimondr Oct 20, 2025
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20 changes: 15 additions & 5 deletions ...ain-base/src/main/java/com/facebook/presto/execution/scheduler/ScaledWriterScheduler.java
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Original file line number Diff line number Diff line change
Expand Up @@ -34,6 +34,7 @@
import static com.facebook.presto.execution.scheduler.ScheduleResult.BlockedReason.WRITER_SCALING;
import static com.facebook.presto.spi.StandardErrorCode.NO_NODES_AVAILABLE;
import static com.facebook.presto.util.Failures.checkCondition;
import static com.google.common.util.concurrent.Futures.nonCancellationPropagating;
import static java.util.Objects.requireNonNull;
import static java.util.concurrent.TimeUnit.MILLISECONDS;

Expand Down Expand Up @@ -73,6 +74,8 @@ public ScaledWriterScheduler(
this.writerMinSizeBytes = requireNonNull(writerMinSize, "minWriterSize is null").toBytes();
this.optimizedScaleWriterProducerBuffer = optimizedScaleWriterProducerBuffer;
this.initialTaskCount = requireNonNull(initialTaskCount, "initialTaskCount is null");

future.set(null);
}

public void finish()
Expand All @@ -84,13 +87,20 @@ public void finish()
@Override
public ScheduleResult schedule()
{
List<RemoteTask> writers = scheduleTasks(getNewTaskCount());
List<RemoteTask> writers = ImmutableList.of();

future.set(null);
future = SettableFuture.create();
executor.schedule(() -> future.set(null), 200, MILLISECONDS);
if (future.isDone()) {
writers = scheduleTasks(getNewTaskCount());
future = SettableFuture.create();
executor.schedule(() -> future.set(null), 200, MILLISECONDS);
}

return ScheduleResult.blocked(done.get(), writers, future, WRITER_SCALING, 0);
return ScheduleResult.blocked(
done.get(),
writers,
nonCancellationPropagating(future),
WRITER_SCALING,
0);
}

private int getNewTaskCount()
Expand Down
20 changes: 7 additions & 13 deletions ...to-main-base/src/main/java/com/facebook/presto/execution/scheduler/SqlQueryScheduler.java
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Original file line number Diff line number Diff line change
Expand Up @@ -27,7 +27,6 @@
import com.facebook.presto.execution.RemoteTask;
import com.facebook.presto.execution.RemoteTaskFactory;
import com.facebook.presto.execution.SqlStageExecution;
import com.facebook.presto.execution.StageExecutionId;
import com.facebook.presto.execution.StageExecutionInfo;
import com.facebook.presto.execution.StageExecutionState;
import com.facebook.presto.execution.StageId;
Expand Down Expand Up @@ -424,7 +423,6 @@ private void schedule()
Set<StageId> completedStages = new HashSet<>();

List<ExecutionSchedule> sectionExecutionSchedules = new LinkedList<>();
Map<StageExecutionId, ListenableFuture<?>> blockedStages = new HashMap<>();

while (!Thread.currentThread().isInterrupted()) {
// remove finished section
Expand All @@ -447,6 +445,8 @@ private void schedule()
.forEach(sectionExecutionSchedules::add);

while (sectionExecutionSchedules.stream().noneMatch(ExecutionSchedule::isFinished)) {
List<ListenableFuture<?>> blockedStages = new ArrayList<>();
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@sourcery-ai sourcery-ai bot Oct 20, 2025

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issue (bug_risk): Switching from a Map to a List for blockedStages may affect duplicate handling.

The previous Map structure ensured each stage was only tracked once, preventing duplicates. With a List, the same stage could be added multiple times, potentially causing redundant actions. Please review if this could introduce bugs when a stage is scheduled more than once before completion.


List<StageExecutionAndScheduler> executionsToSchedule = sectionExecutionSchedules.stream()
.flatMap(schedule -> schedule.getStagesToSchedule().stream())
.collect(toImmutableList());
Expand All @@ -459,12 +459,6 @@ private void schedule()
SqlStageExecution stageExecution = stageExecutionAndScheduler.getStageExecution();
stageExecution.beginScheduling();

ListenableFuture<?> stillBlocked = blockedStages.get(stageExecution.getStageExecutionId());
if (stillBlocked != null && !stillBlocked.isDone()) {
continue;
}
blockedStages.remove(stageExecution.getStageExecutionId());

// perform some scheduling work
ScheduleResult result = stageExecutionAndScheduler.getStageScheduler()
.schedule();
Expand All @@ -482,7 +476,7 @@ private void schedule()
stageExecution.schedulingComplete();
}
else if (!result.getBlocked().isDone()) {
blockedStages.put(stageExecution.getStageExecutionId(), result.getBlocked());
blockedStages.add(result.getBlocked());
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issue (bug_risk): Adding blocked futures to a List may allow duplicates for the same stage.

Previously, the Map ensured only one future per stage; switching to a List allows multiple futures for the same stage if schedule() is called repeatedly before completion. This may lead to redundant cancellations and missed wake-ups if futures aren't managed correctly.

}
else {
allBlocked = false;
Expand Down Expand Up @@ -547,12 +541,12 @@ else if (!result.getBlocked().isDone()) {
// wait for a state change and then schedule again
if (allBlocked && !blockedStages.isEmpty()) {
try (TimeStat.BlockTimer timer = schedulerStats.getSleepTime().time()) {
tryGetFutureValue(whenAnyComplete(blockedStages.values()), 1, SECONDS);
}
for (ListenableFuture<?> blockedStage : blockedStages.values()) {
blockedStage.cancel(true);
tryGetFutureValue(whenAnyComplete(blockedStages), 1, SECONDS);
}
}
for (ListenableFuture<?> blockedStage : blockedStages) {
blockedStage.cancel(true);
}
}
}

Expand Down
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