t8y2/dbx · error

decode ZooKeeper session timeout: %w

Error message

decode ZooKeeper session timeout: %w

What it means

The second int32 in the ZooKeeper connect response is the negotiated session timeout; if the decoder cannot extract it, this wrapped error is returned. Like the protocol-version decode, it indicates the response frame is too short or does not follow the ConnectResponse wire format.

Source

Thrown at agents/drivers/argo-go/zookeeper_protocol.go:167

	request := &zooKeeperEncoder{}
	request.int32(zooKeeperProtocolVersion)
	request.int64(0)
	request.int32(zooKeeperTimeoutMillis(timeout))
	request.int64(0)
	request.bytes(make([]byte, 16))
	if err := client.writeFrame(request.data()); err != nil {
		return nil, fmt.Errorf("send ZooKeeper connect request: %w", err)
	}
	response, err := client.readFrame()
	if err != nil {
		return nil, fmt.Errorf("read ZooKeeper connect response: %w", err)
	}
	decoder := newZooKeeperDecoder(response)
	if _, err := decoder.int32(); err != nil {
		return nil, fmt.Errorf("decode ZooKeeper protocol version: %w", err)
	}
	if _, err := decoder.int32(); err != nil {
		return nil, fmt.Errorf("decode ZooKeeper session timeout: %w", err)
	}
	sessionID, err := decoder.int64()
	if err != nil {
		return nil, fmt.Errorf("decode ZooKeeper session ID: %w", err)
	}
	if _, err := decoder.bytes(); err != nil {
		return nil, fmt.Errorf("decode ZooKeeper session password: %w", err)
	}
	if sessionID == 0 {
		return nil, zk.ErrSessionExpired
	}
	return client, nil
}

func zooKeeperTimeoutMillis(timeout time.Duration) int32 {
	milliseconds := timeout.Milliseconds()
	if milliseconds < 1 {
		return 1

View on GitHub (pinned to c0390bff16)

Solutions

1. Verify the response frame length against the expected ConnectResponse layout (negotiated timeout, session id, passwd)
2. Bypass or reconfigure any TCP proxy/middleware and test a direct connection to ZooKeeper
3. Fix the test fake to emit a complete, well-formed connect response
4. Ensure client and server ZooKeeper protocol versions are compatible

func frameHasTimeout(decoder *zooKeeperDecoder) bool {
    return decoder.remaining() >= 4 // timeout int32 after the version field
}

client, err := newProtocolZooKeeperClient(conn, timeout)
if err != nil {
    if strings.Contains(err.Error(), "decode ZooKeeper session timeout") {
        log.Error("truncated ZK connect response; check proxy MTU/framing")
        return err
    }
    return err
}

When it happens

Trigger: newProtocolZooKeeperClient decoding a response whose payload ends after the first int32 (fewer than 8 bytes total in the expected positions) — truncated frames from a broken proxy or a fake/test server emitting malformed data.

Common situations: Custom or middlebox proxies truncating frames; hand-rolled test doubles returning incomplete responses; memory corruption/short writes between server and client; version skew producing a different field order.

Understand the failure class

• Timeouts: ETIMEDOUT, deadlines, and hung requests — what actually expires when a request times out.

Related errors

• decode ZooKeeper protocol version: %w
• decode ZooKeeper session ID: %w
• decode ZooKeeper session password: %w
• decode ZooKeeper SASL round %d: %w
• ZooKeeper sent an unexpected token after GSSAPI completion

AI-assisted analysis of t8y2/dbx@c0390bff16 (2026-09-05). Data as JSON: /api/errors/b343639bca186875. Report an issue: GitHub.