googleapis/mcp-toolbox · error

failed to register custom client: %w

Error message

failed to register custom client: %w

What it means

trinogo.RegisterCustomClient failed while registering the insecure HTTP client created because disableSslVerification was set — the derived client name (insecure_trino_client_<name>) collides with an already-registered client.

Source

Thrown at internal/sources/trino/trino.go:190

	dsn, err := buildTrinoDSN(host, port, user, password, catalog, schema, queryTimeout, accessToken, kerberosEnabled, sslEnabled, sslCertPath, sslCert)
	if err != nil {
		return nil, fmt.Errorf("failed to build DSN: %w", err)
	}

	logger, err := util.LoggerFromContext(ctx)
	if err != nil {
		return nil, fmt.Errorf("unable to get logger from ctx: %s", err)
	}

	if disableSslVerification {
		logger.WarnContext(ctx, "SSL verification is disabled for trino source %s. This is an insecure setting and should not be used in production.\n", name)
		tr := &http.Transport{
			TLSClientConfig: &tls.Config{InsecureSkipVerify: true},
		}
		client := &http.Client{Transport: tr}
		clientName := fmt.Sprintf("insecure_trino_client_%s", name)
		if err := trinogo.RegisterCustomClient(clientName, client); err != nil {
			return nil, fmt.Errorf("failed to register custom client: %w", err)
		}
		dsn = fmt.Sprintf("%s&custom_client=%s", dsn, clientName)
	}

	db, err := sql.Open("trino", dsn)
	if err != nil {
		return nil, fmt.Errorf("failed to open connection: %w", err)
	}

	// Configure connection pool
	db.SetMaxOpenConns(10)
	db.SetMaxIdleConns(5)
	db.SetConnMaxLifetime(time.Hour)

	return db, nil
}

func buildTrinoDSN(host, port, user, password, catalog, schema, queryTimeout, accessToken string, kerberosEnabled, sslEnabled bool, sslCertPath, sslCert string) (string, error) {

View on GitHub (pinned to 8cc6e09de2)

Solutions

1. Use unique source names when multiple sources disable SSL verification
2. Restart the process to clear the global client registry
3. Prefer proper TLS certificates over disabling verification

When it happens

Trigger: Thrown at internal/sources/trino/trino.go:190 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of googleapis/mcp-toolbox@8cc6e09de2 (2026-09-05). Data as JSON: /api/errors/e1b74d7fbb75acfa. Report an issue: GitHub.