apache/druid · error · IllegalArgumentException

Descriptor string does not have valid Base64 encoding

Error message

Descriptor string does not have valid Base64 encoding

What it means

Encoding validation in InlineDescriptorProtobufBytesDecoder.loadFileDescriptorSet: the descriptor string could not be base64-decoded, so the inline descriptor spec contains characters outside the base64 alphabet or invalid padding, and no descriptor can be built.

Solutions

1. Re-encode the descriptor file with standard base64 (with padding) and paste the full string into descriptor.
2. Check for whitespace/newlines or truncation introduced when copying the spec.

When it happens

Trigger: Thrown at extensions-core/protobuf-extensions/src/main/java/org/apache/druid/data/input/protobuf/InlineDescriptorProtobufBytesDecoder.java:71 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of apache/druid@9b90983fd2 (2026-09-07). Data as JSON: /api/errors/d84331472ba04fc3. Report an issue: GitHub.

Appendix: source

Thrown at extensions-core/protobuf-extensions/src/main/java/org/apache/druid/data/input/protobuf/InlineDescriptorProtobufBytesDecoder.java:71

  {
    return descriptorString;
  }

  @Override
  protected DescriptorProtos.FileDescriptorSet loadFileDescriptorSet()
  {
    try {
      byte[] decodedDesc = StringUtils.decodeBase64String(descriptorString);

      final var descriptorSet = DescriptorProtos.FileDescriptorSet.parseFrom(decodedDesc);
      if (descriptorSet.getFileCount() == 0) {
        throw new ParseException(null, "No file descriptors found in the descriptor set");
      }

      return descriptorSet;
    }
    catch (IllegalArgumentException e) {
      throw new IAE("Descriptor string does not have valid Base64 encoding");
    }
    catch (IOException e) {
      throw new ParseException(descriptorString, e, "Failed to initialize descriptor");
    }
  }

  @Override
  public boolean equals(Object o)
  {
    if (this == o) {
      return true;
    }
    if (o == null || getClass() != o.getClass()) {
      return false;
    }
    if (!super.equals(o)) {
      return false;
    }

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