apache/beam · error · java.lang.RuntimeException

Failed to get field from proto. field

Error message

Failed to get field from proto. field: %s

What it means

FromProtoGetter.getFromProto reads a field value off a proto Message and converts it to a Beam value. Any RuntimeException raised while reading/converting the field is wrapped in a RuntimeException identifying the schema field name, so the original cause (type mismatch, null handling, converter failure) is preserved as the cause chain.

Solutions

  1. Read the cause of the wrapped RuntimeException to find the actual failure
  2. Verify the proto Message class and descriptor match the schema the converter was built from
  3. Rebuild the schema/converter after changing the proto definition (stale descriptors are common)
  4. Log field.getName() and check the offending field's type/optional-ness

Example fix

// before
Row row = ProtoUtils.rowFromMessage(msg); // throws 'Failed to get field from proto. field: foo'
// after
try { Row row = ProtoUtils.rowFromMessage(msg); } catch (RuntimeException e) { LOG.error("field {} failed: ", e.getCause()); }
Defensive patterns

Strategy: try-catch

Validate before calling

// ensure message descriptor matches the one used to build the schema
if (!message.getDescriptorForType().getFullName().equals(expectedDescriptor.getFullName())) throw new IllegalStateException("descriptor mismatch");

Try / catch

try { Row row = converter.apply(message); } catch (RuntimeException e) { LOG.error("proto->Beam failed on field {}, cause: {}", e.getMessage(), e.getCause()); throw e; }

Prevention

When it happens

Trigger: Calling getFromProto during proto-to-Beam Row conversion when message.getField(fieldDescriptor) or the field's converter throws (e.g. field descriptor not found on the message, conversion type error).

Common situations: Schema/proto descriptor drift (message class changed after schema was built); passing a Message instance that doesn't match the descriptor; a custom converter for the field failing.

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/348f38ce404ca4b3. Report an issue: GitHub.

Appendix: source

Thrown at sdks/java/extensions/protobuf/src/main/java/org/apache/beam/sdk/extensions/protobuf/ProtoBeamConverter.java:412

        Descriptors.Descriptor descriptor = message.getDescriptorForType();
        Descriptors.FieldDescriptor fieldDescriptor =
            Preconditions.checkNotNull(descriptor.findFieldByName(field.getName()));

        @Nullable Object protoValue;
        if (field.getType().getNullable()
            && ProtoSchemaTranslator.isNullable(fieldDescriptor)
            && !message.hasField(fieldDescriptor)) {
          // Set null field value only if the Beam field type is nullable and the proto value is
          // null,
          protoValue = null;
        } else {
          // can be a default value. e.g., an optional field.
          protoValue = message.getField(fieldDescriptor);
        }

        return protoValue != null ? converter.convert((@NonNull ProtoT) protoValue) : null;
      } catch (RuntimeException e) {
        throw new RuntimeException(
            String.format("Failed to get field from proto. field: %s", field.getName()), e);
      }
    }
  }

  static class FromProtoOneOfGetter implements FromProtoGetter<OneOfType.@Nullable Value> {
    private final Schema.Field field;
    private final OneOfType oneOfType;
    private final Map<String, ProtoToBeamConverter<Object, Object>> converter;

    FromProtoOneOfGetter(Schema.Field field) {
      this.field = field;
      this.oneOfType = Preconditions.checkNotNull(field.getType().getLogicalType(OneOfType.class));
      this.converter = createConverters(oneOfType.getOneOfSchema());
    }

    private static Map<String, ProtoToBeamConverter<Object, Object>> createConverters(
        Schema schema) {

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