t8y2/dbx · error

ZooKeeper connection is nil

Error message

ZooKeeper connection is nil

What it means

newProtocolZooKeeperClient wraps an established net.Conn into the protocol-level ZooKeeper client and immediately rejects a nil connection. This guards against constructing a client whose subsequent writes would panic on nil. Note the same error symbol exists in both hive-go and argo-go driver copies.

Source

Thrown at agents/drivers/hive-go/zookeeper_protocol.go:143

		events := make(chan zk.Event, 1)
		events <- zk.Event{State: zk.StateHasSession, Server: address}
		close(events)
		return client, events, nil
	}
	return nil, nil, fmt.Errorf("connect and authenticate to ZooKeeper: %s", strings.Join(failures, "; "))
}

type protocolZooKeeperClient struct {
	connection net.Conn
	timeout    time.Duration
	xid        int32
	mutex      sync.Mutex
	closed     bool
}

func newProtocolZooKeeperClient(connection net.Conn, timeout time.Duration) (*protocolZooKeeperClient, error) {
	if connection == nil {
		return nil, errors.New("ZooKeeper connection is nil")
	}
	if timeout <= 0 {
		timeout = defaultConnectTimeout
	}
	client := &protocolZooKeeperClient{connection: connection, timeout: timeout}
	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)
	}

View on GitHub (pinned to c0390bff16)

Solutions

1. Always check the error from the dial/connect step before calling newProtocolZooKeeperClient
2. Fix callers that ignore the (conn, err) pair from connectKerberosZooKeeper/connectZooKeeper
3. Ensure dial helpers never return nil conn with nil error
4. In tests, pass a real or stub net.Conn (e.g. net.Pipe) rather than nil

Example fix

// before
conn, _, _ := connectKerberosZooKeeper(ctx, servers, timeout, tls, cfg)
client, err := newProtocolZooKeeperClient(conn, timeout)
// after
conn, _, err := connectKerberosZooKeeper(ctx, servers, timeout, tls, cfg)
if err != nil {
    return err
}
client, err := newProtocolZooKeeperClient(conn, timeout)

// Go
if conn == nil {
    return errors.New("cannot create ZooKeeper client: connection is nil")
}

// Go
func isLiveConn(c net.Conn) bool { return c != nil }

if isLiveConn(conn) {
    client, err := newProtocolZooKeeperClient(conn, timeout)
    ...
}

When it happens

Trigger: Calling newProtocolZooKeeperClient with a nil net.Conn — usually because the preceding dial/ZooKeeper connect returned (nil, nil, err) and the error was ignored or the nil conn was passed through unconditionally.

Common situations: Caller does `conn, _, _ := connectKerberosZooKeeper(...)` discarding the error and then builds the client; a helper returns nil conn on a non-error path by mistake; test scaffolding passes a stub that is nil.

Related errors

• ZooKeeper sent an unexpected token after GSSAPI completion
• decode ZooKeeper SASL round %d: %w
• ZooKeeper GSSAPI negotiation exceeded %d rounds
• ZooKeeper response XID %d does not match request XID %d
• ZooKeeper session closed because SASL authentication is requ

AI-assisted analysis of t8y2/dbx@c0390bff16 (2026-09-05). Data as JSON: /api/errors/40ab09f7642f1fe8. Report an issue: GitHub.