What causes "Unknown identifier int name" in dianping/cat?

Enable a hex/UTF-8 dump of the buffer at the failure point to see which character was read (the exception does not include it).

dianping/cat · critical · RuntimeException

Unknown identifier int name

Error message

Unknown identifier int name

What it means

PlainTextMessageCodec.decodeLine switches on a single-byte identifier at the start of each line ('t','T','E','M','H','L'...). The default branch throws RuntimeException("Unknown identifier int name") — the message text is garbled ('int name' for 'identifier') and omits the byte value, but the cause is always a line that starts with an unexpected character.

Source

Thrown at cat-core/src/main/java/com/dianping/cat/message/codec/PlainTextMessageCodec.java:268

			tree.findOrCreateHeartbeats().add(heartbeat);

			String heartbeatStatus = helper.read(ctx, TAB);
			String heartbeatData = helper.read(ctx, TAB);

			helper.read(ctx, LF); // get rid of line feed
			heartbeat.setTimestamp(m_dateHelper.parse(timestamp));
			heartbeat.setStatus(heartbeatStatus);
			heartbeat.addData(heartbeatData);

			if (parent != null) {
				parent.addChild(heartbeat);
				return parent;
			} else {
				return heartbeat;
			}
		default:
			throw new RuntimeException("Unknown identifier int name");
		}
	}

	protected void decodeMessage(Context ctx, MessageTree tree) {
		Stack<DefaultTransaction> stack = new Stack<DefaultTransaction>();
		Message parent = decodeLine(ctx, null, stack, tree);

		tree.setMessage(parent);

		while (ctx.getBuffer().readableBytes() > 0) {
			Message message = decodeLine(ctx, (DefaultTransaction) parent, stack, tree);

			if (message instanceof DefaultTransaction) {
				parent = message;
			} else {
				break;
			}
		}

View on GitHub (pinned to e815e74d4c)

Solutions

Enable a hex/UTF-8 dump of the buffer at the failure point to see which character was read (the exception does not include it).
Strip or escape CR/LF in message data strings on the producer side so lines stay intact.
Align client and server versions so both understand the same identifier set.
If constructing payloads manually, start each line with a valid identifier byte ('t','T','E','M','H','L').

Example fix

// before: raw newline inside data breaks next line's identifier
String data = "a\nb"; // next line begins 'b' -> Unknown identifier

// after: sanitize
String data = raw.replace('\n', ' ').replace('\r', ' ');

Defensive patterns

Strategy: try-catch

Try / catch

catch (RuntimeException e) { if ("Unknown identifier int name".equals(e.getMessage())) { abort decoding this payload; log buffer hexdump; } else throw e; }

Prevention

Sanitize CR/LF out of all message data fields before they enter the wire format.
Keep identifier byte vocabulary in sync across versions.
Log the failing byte offset — the exception omits the offending character.

When it happens

Trigger: Decoding a PT1 payload where a line's leading byte is not a known identifier: line desynchronization (a field containing an embedded newline), truncation, or version drift adding a new line type this codec does not support.

Common situations: Event/transaction data strings containing raw newline characters that break the line-oriented format; mixed client/server versions introducing new record types; hand-crafted test payloads with wrong tags.

Related errors

AI-assisted analysis of dianping/cat@e815e74d4c (2026-08-14). Data as JSON: /api/errors/01bad5a7e4c99a10. Report an issue: GitHub.