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[Prism] Fix race condition and nil pointer dereferencing #36370

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Merged
shunping merged 3 commits into from
Oct 3, 2025
Merged

[Prism] Fix race condition and nil pointer dereferencing #36370

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10653c0
Fix race condition when injecting processing-time bundle
shunping Oct 3, 2025
a2b78f6
Fix an issue of dereferencing nil.
shunping Oct 3, 2025
3f88c27
Add comments to explain the nil pointer case.
shunping Oct 3, 2025
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10 changes: 10 additions & 0 deletions sdks/go/pkg/beam/runners/prism/internal/engine/elementmanager.go
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Original file line number Diff line number Diff line change
Expand Up @@ -384,6 +384,7 @@ func (em *ElementManager) Bundles(ctx context.Context, upstreamCancelFn context.
defer func() {
// In case of panics in bundle generation, fail and cancel the job.
if e := recover(); e != nil {
slog.Error("panic in ElementManager.Bundles watermark evaluation goroutine", "error", e, "traceback", string(debug.Stack()))
upstreamCancelFn(fmt.Errorf("panic in ElementManager.Bundles watermark evaluation goroutine: %v\n%v", e, string(debug.Stack())))
}
}()
Expand Down Expand Up @@ -1366,7 +1367,9 @@ func (ss *stageState) injectTriggeredBundlesIfReady(em *ElementManager, window t
// TODO: how to deal with watermark holds for this implicit processing time timer
// ss.watermarkHolds.Add(timer.holdTimestamp, 1)
ss.processingTimeTimers.Persist(firingTime, timer, notYetHolds)
em.refreshCond.L.Lock()
em.processTimeEvents.Schedule(firingTime, ss.ID)
em.refreshCond.L.Unlock()
em.wakeUpAt(firingTime)
}
}
Expand Down Expand Up @@ -1566,6 +1569,13 @@ func (ss *stageState) savePanes(bundID string, panesInBundle []bundlePane) {
func (ss *stageState) buildTriggeredBundle(em *ElementManager, key string, win typex.Window) ([]element, int) {
var toProcess []element
dnt := ss.pendingByKeys[key]
if dnt == nil {
// If we set an after-processing-time trigger, but some other triggers fire or
// the end of window is reached before the first trigger could fire, then
// the pending elements are processed in other bundles, leaving a nil when
// we try to build this triggered bundle.
return toProcess, 0
}
var notYet []element

// Look at all elements for this key, and only for this window.
Expand Down
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