What causes "Unexpected progress shape: %s" in apache/beam?

Inspect the SyntheticOptions in your test pipeline and set the progress shape to LINEAR or LINEAR_REGRESSING.

apache/beam · error · AssertionError

Unexpected progress shape

Error message

Unexpected progress shape: %s

What it means

SyntheticBoundedSource's reader supports configurable progress-reporting shapes (LINEAR, LINEAR_REGRESSING) used to test runner watermark/fraction-consumed handling. getFractionConsumed() throws AssertionError when the configured SyntheticOptions progress shape is not one of the supported enum values, indicating an internal invariant violation or an added enum case not handled in the switch.

Solutions

Inspect the SyntheticOptions in your test pipeline and set the progress shape to LINEAR or LINEAR_REGRESSING.
Fix the options JSON/flag so the parsed enum matches a supported value (watch for typos or parsing producing an unexpected default).
If you added a new shape enum value, add the corresponding case to getFractionConsumed().

Example fix

// before (options JSON)
{"numRecords": 1000, "progressShape": "EXPONENTIAL"}
// after
{"numRecords": 1000, "progressShape": "LINEAR"}

Defensive patterns

Strategy: validation

Validate before calling

// Java — validate progress shape before launching synthetic pipeline
String shape = optionsJson.get("progressShape").asText();
if (!shape.equals("LINEAR") && !shape.equals("LINEAR_REGRESSING")) {
  throw new IllegalArgumentException("Unsupported progressShape: " + shape);
}

Prevention

Only use progress shapes documented for your Beam version (LINEAR, LINEAR_REGRESSING).
Copy option JSON from the matching Beam version's test resources.
If extending the enum, update every switch over it.

When it happens

Trigger: Setting a progress shape in SyntheticOptions (e.g., via synthetic source options JSON in test pipelines) that is neither LINEAR nor LINEAR_REGRESSING, then having the runner call getFractionConsumed(); also hit when a new ProgressDirection enum value is added without updating this switch.

Common situations: Running Beam perf-test harnesses with synthetic source option JSON specifying an unsupported/typo'd shape; internal Beam development when extending progress directions.

Understand the failure class

Background: Invalid enum value errors: "Unknown type", "Invalid scope", "must be one of" — when a string is not on the library's allowed list — this error's family across 23 libraries.

Related errors

AI-assisted analysis of apache/beam@12126d8942 (2026-09-13). Data as JSON: /api/errors/6bb18f6bfdeca090. Report an issue: GitHub.

Appendix: source

Thrown at sdks/java/io/synthetic/src/main/java/org/apache/beam/sdk/io/synthetic/SyntheticBoundedSource.java:248

      return true;
    }

    private boolean shouldSourceSplit() {
      return (splitPointFrequencyRecords == 0) || (currentOffset % splitPointFrequencyRecords == 0);
    }

    @Override
    public Double getFractionConsumed() {
      double realFractionConsumed = super.getFractionConsumed();
      SyntheticSourceOptions.ProgressShape shape = getCurrentSource().sourceOptions.progressShape;
      switch (shape) {
        case LINEAR:
          return realFractionConsumed;
        case LINEAR_REGRESSING:
          return 0.9 - 0.8 * realFractionConsumed;
        default:
          throw new AssertionError("Unexpected progress shape: " + shape);
      }
    }

    @Override
    protected boolean isAtSplitPoint() throws NoSuchElementException {
      return isAtSplitPoint;
    }

    @Override
    public void close() {
      // Nothing
    }
  }
}

View on GitHub (pinned to 12126d8942)