grpc/grpc-java · error · IllegalArgumentException

Unknown Value type:

Error message

Unknown Value type: 

What it means

ProtobufJsonConverter.convertValue converts a google.protobuf.Value into a plain Java object by switching on the Value's kind case. When the kind is not a recognized case (struct/list/number/string/bool/null), it throws an IllegalArgumentException naming the KindCase. This indicates a malformed or unsupported protobuf Value.

Solutions

1. Ensure every google.protobuf.Value in the source config has exactly one kind set
2. Fix the config producer that emitted the unset Value
3. Upgrade the protobuf/grpc-xds libraries if a new Value kind is involved
4. Add upstream validation rejecting Values with KIND_NOT_SET

Example fix

// before: Value with no kind set
Value.newBuilder().build()
// after
Value.newBuilder().setStringValue("prod").build()

if (value.getKindCase() == Value.KindCase.KIND_NOT_SET) { reject("Value has no kind set"); }

null

try { json = ProtobufJsonConverter.convertToJson(struct); }
catch (IllegalArgumentException e) { log.error("Unsupported Value kind", e); treatAsEmpty(); }

When it happens

Trigger: convertToJson encounters a google.protobuf.Value whose kind is KIND_NOT_SET or an unrecognized case from a newer protobuf API version.

Common situations: Proto built without setting any kind field; custom metadata in xDS config carrying an unset Value; protobuf runtime version mismatch between producer and consumer.

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

• ${structOrError.getErrorDetail()}
• ClusterSpecifierPlugin
• Could not parse HttpConnectionManager config from…
• Failed to parse access token credentials: " + e.getMessage()
• Failed to parse channel credentials: " + e.getMessage()

AI-assisted analysis of grpc/grpc-java@64daddc1f3 (2026-09-08). Data as JSON: /api/errors/dced9cf63fbdc5da. Report an issue: GitHub.

Appendix: source

Thrown at xds/src/main/java/io/grpc/xds/internal/ProtobufJsonConverter.java:58

  private static Object convertValue(Value value) {
    switch (value.getKindCase()) {
      case STRUCT_VALUE:
        return convertToJson(value.getStructValue());
      case LIST_VALUE:
        return value.getListValue().getValuesList().stream()
            .map(ProtobufJsonConverter::convertValue)
            .collect(Collectors.toList());
      case NUMBER_VALUE:
        return value.getNumberValue();
      case STRING_VALUE:
        return value.getStringValue();
      case BOOL_VALUE:
        return value.getBoolValue();
      case NULL_VALUE:
        return null;
      default:
        throw new IllegalArgumentException("Unknown Value type: " + value.getKindCase());
    }
  }
}

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