apache/beam · error · java.lang.RuntimeException

Unable to decode constant members from payload for ParamWind

Error message

Unable to decode constant members from payload for ParamWindowedValueCoder: 

What it means

The mirror of error 881: ParamWindowedValueCoder deserializes its constant members from a byte payload in its readObject path; an IOException during decode is wrapped in this RuntimeException. It means the coder payload produced at serialization time cannot be decoded.

Source

Thrown at sdks/java/core/src/main/java/org/apache/beam/sdk/values/WindowedValues.java:1481

    public static WindowedValues.ParamWindowedValueCoder<?> fromComponents(
        List<Coder<?>> components, byte[] payload) {
      Coder<? extends BoundedWindow> windowCoder =
          (Coder<? extends BoundedWindow>) components.get(1);
      WindowedValues.FullWindowedValueCoder<byte[]> windowedValueCoder =
          WindowedValues.FullWindowedValueCoder.of(ByteArrayCoder.of(), windowCoder);

      try {
        ByteArrayInputStream bais = new ByteArrayInputStream(payload);
        WindowedValue<byte[]> windowedValue = windowedValueCoder.decode(bais);
        return WindowedValues.ParamWindowedValueCoder.of(
            components.get(0),
            windowCoder,
            windowedValue.getTimestamp(),
            windowedValue.getWindows(),
            windowedValue.getPaneInfo(),
            windowedValue.getValueKind());
      } catch (IOException e) {
        throw new RuntimeException(
            "Unable to decode constant members from payload for ParamWindowedValueCoder: ", e);
      }
    }

    private void writeObject(ObjectOutputStream out) throws IOException {
      out.defaultWriteObject();
      out.writeObject(getPayload(this));
    }

    private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException {
      in.defaultReadObject();
      byte[] payload = (byte[]) in.readObject();
      ParamWindowedValueCoder<?> paramWindowedValueCoder =
          fromComponents(Arrays.asList(valueCoder, getWindowCoder()), payload);
      this.windowedValuePrototype = paramWindowedValueCoder.windowedValuePrototype;
    }
  }
}

View on GitHub (pinned to 12126d8942)

Solutions

1. Read the 'Caused by' IOException to identify which field failed to decode
2. Ensure identical Beam SDK versions on all environments that serialize/deserialize the coder
3. Re-register custom coders in the deserializing environment
4. Clear stale serialized caches or job artifacts built with older coder versions

Example fix

// before: mismatched SDK versions between submission and worker
// pom.xml: beam-sdks-java-core 2.40.0 (submitter), 2.50.0 (worker)
// after: pin one version everywhere
<dependency>
  <groupId>org.apache.beam</groupId>
  <artifactId>beam-sdks-java-core</artifactId>
  <version>2.50.0</version>
</dependency>

try { decodePayload(bytes); } catch (RuntimeException e) { if (e.getCause() instanceof IOException) { /* rebuild/re-serialize coder with matching SDK version */ } throw e; }

When it happens

Trigger: Deserializing a ParamWindowedValueCoder from its byte payload when the encoded windowed value cannot be decoded - corrupted payload, coder version mismatch, or window coder unable to decode the encoded windows.

Common situations: Beam version differences between serialization and deserialization environments; deserialized coder crossing JVM/worker boundaries with incompatible registered coders; corrupted cached coder payloads.

Understand the failure class

Background: "failed to unmarshal" / json.Unmarshal errors: why parsing a response into a Go struct fails and how to fix it — this error's family across 23 libraries.

• Parsing and encoding errors: unexpected token, malformed input — why parsers reject input and how to find the real culprit.

Related errors

• Invalid encoded string length: {}
• error when decoding a textual integer
• EOF encountered decoding a ValueKind
• Unknown ValueKind number: {}
• Unable to encode constant members of ParamWindowedValueCoder

AI-assisted analysis of apache/beam@12126d8942 (2026-09-13). Data as JSON: /api/errors/3273f4cbcf0d8594. Report an issue: GitHub.