MyCATApache/Mycat-Server · error · RuntimeException

Unknown packet

Error message

Unknown packet

What it means

PacketUtils.parsePacket(byte[], int) parses a stream of PostgreSQL backend messages by their leading type byte, dispatching to parsers like AuthenticationRequest, DataRow, CopyOutResponse, ParseComplete. A type byte with no case in the switch hits default and throws RuntimeException("Unknown packet").

Solutions

1. Add a case for the unknown type byte (from the MyCat log / PG protocol docs) parsing the corresponding packet class
2. Upgrade MyCat to a version with a more complete PG packet parser
3. Patch parsePacket to skip unknown message types gracefully using pg.getLength() instead of throwing
4. Avoid triggering paths that emit unhandled messages (e.g. disable client-side notices, avoid LISTEN/NOTIFY through MyCat)

Example fix

// before
default:
    throw new RuntimeException("Unknown packet");
// after
case 'S':
    pg = ParameterStatus.parse(bytes, offset);
    break;
default:
    LOGGER.warn("Unknown packet type: " + (char) bytes[offset]);
    break;

try { packets = PacketUtils.parsePacket(bytes, offset); } catch (RuntimeException e) { if ("Unknown packet".equals(e.getMessage())) { /* log first type byte, skip or upgrade parser */ } else { throw e; } }

When it happens

Trigger: The PostgreSQL server sends a message type (e.g. 'N' NOTICE, 'S' ParameterStatus, 'K' BackendKeyData, 'A' NotificationResponse, 'G' CopyInResponse, extended-protocol frames) that this byte[]-based switch does not handle.

Common situations: PG servers emitting frequent notices/parameter-status updates; applications using LISTEN/NOTIFY; extended query protocol (Parse/Bind) sessions; mismatched PG server version emitting messages the old MyCat parser lacks.

Related errors

• the select proess err ,the SelectResponse is empty
• Tried to send an out-of-range integer as a 2-byte value
• not a query sql statement
• Unknown Packet!
• unknown status!

AI-assisted analysis of MyCATApache/Mycat-Server@65f8d8beb7 (2026-09-11). Data as JSON: /api/errors/9adb245f84e964a5. Report an issue: GitHub.

Appendix: source

Thrown at src/main/java/io/mycat/backend/postgresql/utils/PacketUtils.java:75

			case 'D':
				pg = DataRow.parse(bytes, offset);
				break;

			case 'I':
				pg = EmptyQueryResponse.parse(bytes, offset);
				break;

			case 'G':
				pg = CopyInResponse.parse(bytes, offset);
				break;
			case 'H':
				pg = CopyOutResponse.parse(bytes, offset);
				break;
			case '1':
				pg = ParseComplete.parse(bytes, offset);
				break;
			default:
				throw new RuntimeException("Unknown packet");
			}
			if (pg != null) {
				offset = offset + pg.getLength() + 1;
				pgs.add(pg);
			}
			
		}
		return pgs;
	}
	
	@Deprecated
	private static List<PostgreSQLPacket> parsePacket(byte[] bytes, int offset,
			int readLength) throws IOException {
		List<PostgreSQLPacket> pgs = new ArrayList<>();
		while (offset < readLength) {
			char MAKE = (char) bytes[offset];
			PostgreSQLPacket pg = null;
			switch (MAKE) {

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