vitessio/vitess · error

no dialer registered for VTGate protocol %s

Error message

no dialer registered for VTGate protocol %s

What it means

vtgateconn.DialProtocol looks up a client dialer in a registry keyed by protocol name (e.g. 'grpc'). If no dialer has been registered for the given protocol string, dialing cannot proceed and this error is returned. It is a pure client-side configuration/naming error.

Source

Thrown at go/vt/vtgate/vtgateconn/vtgateconn.go:270

// DeregisterDialer removes the named DialerFunc from the registered list of
// dialers. If the named DialerFunc does not exist, it is a noop.
//
// This is useful to avoid unbounded memory use if many different dialer
// implementations are used throughout the lifetime of a program.
func DeregisterDialer(name string) {
	dialersM.Lock()
	defer dialersM.Unlock()
	delete(dialers, name)
}

// DialProtocol dials a specific protocol, and returns the *VTGateConn
func DialProtocol(ctx context.Context, protocol string, address string) (*VTGateConn, error) {
	dialersM.Lock()
	dialer, ok := dialers[protocol]
	dialersM.Unlock()

	if !ok {
		return nil, fmt.Errorf("no dialer registered for VTGate protocol %s", protocol)
	}
	impl, err := dialer(ctx, address)
	if err != nil {
		return nil, err
	}
	return &VTGateConn{
		impl: impl,
	}, nil
}

// Dial dials using the command-line specified protocol, and returns
// the *VTGateConn.
func Dial(ctx context.Context, address string) (*VTGateConn, error) {
	return DialProtocol(ctx, vtgateProtocol, address)
}

// DialCustom creates a new VTGateConn with the given DialerFunc.
func DialCustom(ctx context.Context, dialer DialerFunc, address string) (*VTGateConn, error) {

View on GitHub (pinned to 01a25a7d17)

Solutions

1. Use the exact registered protocol name, typically "grpc": vtgateconn.DialProtocol(ctx, "grpc", address)
2. Verify your binary imports the dialer package (e.g. _ "vitess.io/vitess/go/vt/vtgate/grpcvtgateconn") so its init registers the dialer
3. Print registered keys or check code: dialers map keys in vtgateconn
4. If using a smart client (DialVTGate / go/vt/discovery), confirm the vtgate address scheme matches a supported protocol

Example fix

// before
conn, err := vtgateconn.DialProtocol(ctx, "grpcs", "localhost:15991")
// after
import _ "vitess.io/vitess/go/vt/vtgate/grpcvtgateconn"
conn, err := vtgateconn.DialProtocol(ctx, "grpc", "localhost:15991")

// Go: verify the grpc dialer is registered before dialing
import _ "vitess.io/vitess/go/vt/vtgate/grpcvtgateconn"

func protocolSupported(p string) bool {
    return p == "grpc" // dialers registry keys; check vtgateconn source for others
}

conn, err := vtgateconn.DialProtocol(ctx, "grpc", addr)
if err != nil {
    if strings.Contains(err.Error(), "no dialer registered") {
        return nil, fmt.Errorf("protocol %q unavailable: ensure grpcvtgateconn is imported", addr)
    }
    return nil, err
}

When it happens

Trigger: Calling vtgateconn.DialProtocol(ctx, protocol, address) with a protocol string that was never registered via RegisterDialer, e.g. typo 'grpcs', or a build/tag that excludes the grpc dialer registration.

Common situations: Typos in the protocol part of a vtgate address ('grpc' vs 'grpc+' prefix confusion), using a custom binary that does not import the grpc dialer package, or tests/tools built without the expected dialer registration.

Related errors

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• --buffer-window must be >= 1s (specified value: %v)
• --buffer-window must be <= --buffer-max-failover-duration: %

AI-assisted analysis of vitessio/vitess@01a25a7d17 (2026-09-01). Data as JSON: /api/errors/54daa7354af8cd69. Report an issue: GitHub.