apache/cassandra · error · ProtocolException

Unknown kind id in RESULT message

Error message

Unknown kind id %d in RESULT message

What it means

Every RESULT message body starts with a kind id (Rows 0x02, SetKeyspace 0x03, Prepared 0x04, SchemaChange 0x05, Void 0x01). Kind.fromId throws a ProtocolException when the id does not map to a known kind — meaning the server produced, or the client decoded, a result payload with an unrecognized kind byte.

Solutions

1. Verify the client driver version matches the server protocol version and upgrade it
2. Inspect the raw frame (hex dump) to confirm the message body wasn't truncated or corrupted in transit
3. Check for intermediaries (proxies, LBs) that rewrite/mangle frames
4. If writing a custom codec, only emit ids from the protocol spec's RESULT kind table

Example fix

// before
int kind = buffer.readInt(); // garbage due to truncated frame
// after
if (buffer.readableBytes() < 4)
    throw new DecoderException("truncated RESULT frame");
int kind = buffer.readInt();

if (buffer.readableBytes() < 4)
    throw new DecoderException("RESULT frame truncated before kind id");

boolean isKnownResultKind(int id) {
    return id >= 0x01 && id <= 0x05; // Void..SchemaChange
}

try {
    ResultMessage msg = ResultMessage.decoder.decode(frame);
} catch (ProtocolException e) {
    if (e.getMessage().contains("Unknown kind id")) {
        log.warn("malformed RESULT frame; reconnecting", e);
        reconnect();
    } else throw e;
}

When it happens

Trigger: Decoding a RESULT frame whose first int is not one of the registered kind ids — a corrupt/truncated frame, a client and server with mismatched protocol expectations, or a hand-rolled client crafting an invalid kind id.

Common situations: Buggy third-party drivers or proxies generating malformed result frames; version skew between a custom parser and the server protocol; fuzzers/protocol conformance tests sending arbitrary ids.

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

• Missing value CQL_VERSION in STARTUP message
• The page size cannot be 0
• The page size cannot be 0
• There were markers(?) in CQL but bound variables
• A TTL must be greater or equal to 0, but was

AI-assisted analysis of apache/cassandra@88fd0f6a0e (2026-09-10). Data as JSON: /api/errors/2b6d057e3d1cdbf6. Report an issue: GitHub.

Appendix: source

Thrown at src/java/org/apache/cassandra/transport/messages/ResultMessage.java:91

            for (Kind k : Kind.values())
            {
                if (ids[k.id] != null)
                    throw new IllegalStateException("Duplicate kind id");
                ids[k.id] = k;
            }
        }

        private Kind(int id, Message.Codec<ResultMessage> subcodec)
        {
            this.id = id;
            this.subcodec = subcodec;
        }

        public static Kind fromId(int id)
        {
            Kind k = ids[id];
            if (k == null)
                throw new ProtocolException(String.format("Unknown kind id %d in RESULT message", id));
            return k;
        }
    }

    public final Kind kind;

    protected ResultMessage(Kind kind)
    {
        super(Message.Type.RESULT);
        this.kind = kind;
    }

    public static class Void extends ResultMessage
    {
        // Even though we have no specific information here, don't make a
        // singleton since as each message it has in fact a streamid and connection.
        public Void()
        {

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