apache/beam · error · UnsupportedOperationException

Cannot outputWithTimestamp from TruncateRestriction

Error message

Cannot outputWithTimestamp from TruncateRestriction

What it means

The receiver provided to the @TruncateRestriction callback of a Splittable DoFn cannot emit elements with timestamps. TruncateRestriction only produces a replacement restriction when checkpointing/truncation occurs, so any element output is a model violation and throws UnsupportedOperationException.

Solutions

1. Remove element output from @TruncateRestriction; only output a new restriction (or return nothing to signal no truncation).
2. Move result emission into @ProcessElement where the restriction tracker permits output.
3. If partial-result flushing is needed, use bundle finalization or state/timers instead.

Example fix

// before
@TruncateRestriction void truncate(@Restriction Restriction r, OutputReceiver<Restriction> out) { out.outputWithTimestamp(r, now); }
// after
@TruncateRestriction void truncate(@Restriction Restriction r, OutputReceiver<Restriction> out) { /* no output or out.output(newRestriction) */ }

boolean isTruncateRestrictionContext = ctx instanceof SplittableTruncateSizedRestrictionsDoFnRunner.TruncateRestrictionContext; // do not emit if true

try { out.outputWithTimestamp(r, ts); } catch (UnsupportedOperationException e) { LOG.error("Emitting from truncateRestriction is unsupported"); }

When it happens

Trigger: Calling outputWithTimestamp from inside a @TruncateRestriction method's OutputReceiver.

Common situations: Attempting to flush partial results during truncation/checkpoint; developers confusing truncateRestriction with processElement output semantics.

Understand the failure class

Background: UnsupportedOperationException and "is not supported" errors: when a library deliberately refuses a call — this error's family across 30 libraries.

Related errors

• Cannot outputWindowedValue from TruncateRestriction
• Cannot outputWithTimestamp from SplitRestriction
• RecordId unsupported in
• RecordOffset unsupported in
• Restriction unsupported in

AI-assisted analysis of apache/beam@12126d8942 (2026-09-13). Data as JSON: /api/errors/c747ccab8d0671ef. Report an issue: GitHub.

Appendix: source

Thrown at sdks/java/harness/src/main/java/org/apache/beam/fn/harness/SplittableTruncateSizedRestrictionsDoFnRunner.java:925

    @Override
    @SuppressWarnings("nullness")
    public Object watermarkEstimatorState() {
      return getCurrentWatermarkEstimatorState();
    }

    @Override
    public RestrictionTracker<?, ?> restrictionTracker() {
      return getCurrentTracker();
    }

    @Override
    public PipelineOptions pipelineOptions() {
      return pipelineOptions;
    }

    @Override
    public void outputWithTimestamp(RestrictionT output, Instant timestamp) {
      throw new UnsupportedOperationException(
          "Cannot outputWithTimestamp from TruncateRestriction");
    }

    @Override
    public void outputWindowedValue(
        RestrictionT output,
        Instant timestamp,
        Collection<? extends BoundedWindow> windows,
        PaneInfo paneInfo) {
      throw new UnsupportedOperationException(
          "Cannot outputWindowedValue from TruncateRestriction");
    }
  }

  /**
   * Passes split requests downstream, by way of trySplit on the overall runner, which will split
   * per window if needed.
   */

View on GitHub (pinned to 12126d8942)