apache/beam · error · IllegalStateException

translated with URN ' ' but payload was not a

Error message

%s translated %s with URN '%s' but payload was not a %s

What it means

WindowIntoTranslation.getWindowIntoPayload() parses the payload of a PTransform whose URN is ASSIGN_WINDOWS, expecting a serialized WindowIntoPayload protobuf. If protobuf parsing fails (InvalidProtocolBufferException), it throws this IllegalStateException indicating the transform that claimed to be a window-assignment transform has a payload of the wrong type.

Solutions

  1. Regenerate/retranslate the pipeline with the same Beam SDK version so the payload is a proper WindowIntoPayload.
  2. Verify no code manually writes PTransform specs with the assign-windows URN and a foreign payload.
  3. Check runner/SDK version compatibility; upgrade the runner harness to a matching Beam version.
  4. Inspect the failing transform's spec payload bytes to identify what actually got serialized.

Example fix

// before: manually building an assign-windows transform with a foreign payload
PTransform.newBuilder().setSpec(FunctionSpec.newBuilder().setUrn(ASSIGN_WINDOWS_URN)
    .setPayload(anyOtherProtoBytes)).build();
// after: let translation build it from WindowInto
pc.apply(Window.into(FixedWindows.of(Duration.standardMinutes(1))));
Defensive patterns

Strategy: try-catch

Validate before calling

// Validate the transform proto payload parses before translating
try {
  WindowIntoPayload.parseFrom(transformProto.getSpec().getPayload());
} catch (InvalidProtocolBufferException e) {
  throw new IllegalStateException("Assign-windows transform payload is not a WindowIntoPayload", e);
}

Try / catch

try {
  strategy = WindowingStrategyTranslation.fromProto(windowingStrategyProto);
} catch (IllegalStateException e) {
  if (String.valueOf(e.getMessage()).contains("payload was not a")) {
    // regenerate/retranslate the pipeline with a matching Beam version
  }
  throw e;
}

Prevention

When it happens

Trigger: Rehydrating a pipeline proto (e.g. a runner reading a submitted job graph, or BeamFnApi translation) where the transform with URN 'beam:transform:assign_windows:v1' has a spec payload that is not a valid serialized WindowIntoPayload — corrupted graph, hand-crafted proto, or a runner/SDK version mismatch producing a different payload message.

Common situations: Custom runners deserializing job protos produced by a different Beam version; pipelines built/modified programmatically that put the wrong payload into an assign-windows PTransform; corrupted job submissions.

Understand the failure class

Background: "cannot parse invalid wire-format data", "cannot unmarshal", "failed unmarshalling": protobuf unmarshal errors explained — this error's family across 10 libraries.

Related errors

AI-assisted analysis of apache/beam@12126d8942 (2026-09-13). Data as JSON: /api/errors/d55088a06bb43cad. Report an issue: GitHub.

Appendix: source

Thrown at sdks/java/core/src/main/java/org/apache/beam/sdk/util/construction/WindowIntoTranslation.java:93

      transformProto =
          PTransformTranslation.toProto(application, Collections.emptyList(), components);
    } catch (IOException exc) {
      throw new RuntimeException(exc);
    }

    checkArgument(
        PTransformTranslation.ASSIGN_WINDOWS_TRANSFORM_URN.equals(
            transformProto.getSpec().getUrn()),
        "Illegal attempt to extract %s from transform %s with name \"%s\" and URN \"%s\"",
        Window.Assign.class.getSimpleName(),
        application.getTransform(),
        application.getFullName(),
        transformProto.getSpec().getUrn());

    try {
      return WindowIntoPayload.parseFrom(transformProto.getSpec().getPayload());
    } catch (InvalidProtocolBufferException exc) {
      throw new IllegalStateException(
          String.format(
              "%s translated %s with URN '%s' but payload was not a %s",
              PTransformTranslation.class.getSimpleName(),
              application,
              PTransformTranslation.ASSIGN_WINDOWS_TRANSFORM_URN,
              WindowIntoPayload.class.getSimpleName()),
          exc);
    }
  }

  public static @Nullable WindowFn<?, ?> getWindowFn(AppliedPTransform<?, ?, ?> application) {
    return WindowingStrategyTranslation.windowFnFromProto(
        getWindowIntoPayload(application).getWindowFn());
  }

  /** A {@link PTransformTranslation.TransformPayloadTranslator} for {@link Window}. */
  public static class WindowIntoPayloadTranslator
      implements PTransformTranslation.TransformPayloadTranslator<Window.Assign<?>> {

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