vitessio/vitess · error

error dialing vtgate: %w

Error message

error dialing vtgate: %w

What it means

The vtadmin vtsql package dials vtgate over gRPC when constructing a V3 connection (New -> dial). If the dial function (grpc.DialContext) returns an error — typically network or TLS-level — it is wrapped as 'error dialing vtgate'. This happens during client construction, before any query is executed.

Source

Thrown at go/vt/vtadmin/vtsql/vtsql.go:160

	vtadminproto.AnnotateClusterSpan(vtgate.cluster, span)
	span.Annotate("is_using_credentials", vtgate.creds != nil)

	conf := vitessdriver.Configuration{
		Protocol:        "grpc_" + vtgate.cluster.Id,
		Address:         resolver.DialAddr(vtgate.resolver, "vtgate"),
		Target:          target,
		GRPCDialOptions: append(opts, grpc.WithTransportCredentials(insecure.NewCredentials()), grpc.WithResolvers(vtgate.resolver)),
	}

	if vtgate.creds != nil {
		conf.GRPCDialOptions = append([]grpc.DialOption{
			grpc.WithPerRPCCredentials(vtgate.creds),
		}, conf.GRPCDialOptions...)
	}

	vtgate.conn, err = vtgate.dialFunc(conf)
	if err != nil {
		return fmt.Errorf("error dialing vtgate: %w", err)
	}

	log.Info("Established gRPC connection to vtgate\n")

	vtgate.m.Lock()
	defer vtgate.m.Unlock()

	vtgate.closed = false
	vtgate.dialedAt = time.Now()

	return nil
}

// ShowTablets is part of the DB interface.
func (vtgate *VTGateProxy) ShowTablets(ctx context.Context) (*sql.Rows, error) {
	span, ctx := trace.NewSpan(ctx, "VTGateProxy.ShowTablets")
	defer span.Finish()

View on GitHub (pinned to 01a25a7d17)

Solutions

1. Confirm vtgate is running and the vtadmin config's hostname/port point at it (nc/curl the gRPC port).
2. If TLS is enabled, verify the CA cert, client cert/key, and server name match; check vtgate's -grpc_cert/-grpc_key flags.
3. Check DNS/network reachability from the vtadmin host/pod to the vtgate address.
4. Review dialFunc options and grpc.Dial timeout/lazy-connect behavior; with WithBlock semantics, connectivity errors surface here.

Example fix

// before
vtsql.New(ctx, cfg) // cfg.VtgateHost = "vtgate:15991" (stale port)
// after
vtsql.New(ctx, cfg) // cfg.VtgateHost = "vtgate:15999" (actual vtgate grpc port)

// Go: probe vtgate reachability before dialing
func vtgateReachable(host string, port int, timeout time.Duration) bool {
    conn, err := net.DialTimeout("tcp", fmt.Sprintf("%s:%d", host, port), timeout)
    if err != nil { return false }
    conn.Close()
    return true
}

vtg, err := vtsql.New(ctx, cfg)
if err != nil {
    if strings.Contains(err.Error(), "error dialing vtgate") {
        // backoff and retry; verify vtgate address/TLS in the meantime
    }
}

When it happens

Trigger: Creating a new vtsql connection (vtsql.New with Parse'd config) where vtgate is unreachable: wrong hostname/port, vtgate process down, TLS handshake failure, or DNS resolution failure in dialFunc.

Common situations: vtgate not running or restarted; wrong --vtctld/vtgate port in vtadmin config; firewall or NetworkPolicy blocking the gRPC port; certificate/key mismatch when TLS is enabled; DNS name not resolvable from the vtadmin pod.

Understand the failure class

Background: ECONNREFUSED and "connection refused" / "could not connect to server" errors: what they mean and how to fix them — this error's family across 44 libraries.

Related errors

• gRPC connection wait time exceeded
• error dialing binlog server: %v
• error received from Stream %v
• failed to GetCellInfos for cluster %s: %w
• GetKeyspaces(cluster = %s): %w

AI-assisted analysis of vitessio/vitess@01a25a7d17 (2026-09-01). Data as JSON: /api/errors/cdf8e15a5825fb28. Report an issue: GitHub.