What causes "unable to connect successfully: %w" in googleapis/mcp-toolbox?

Verify user/password with a direct MySQL client against the MindsDB server

unable to connect successfully: %w

Error message

unable to connect successfully: %w

What it means

After successfully creating the pool, Initialize calls PingContext to verify a real connection can be established; failure means the pool exists but MindsDB rejected or timed out the connection. The pool is closed and initialization fails. This is distinct from pool-creation failure: auth or network problems happen at ping time.

Source

Thrown at internal/sources/mindsdb/mindsdb.go:73

	Password     string `yaml:"password"`
	Database     string `yaml:"database" validate:"required"`
	QueryTimeout string `yaml:"queryTimeout"`
}

func (r Config) SourceConfigType() string {
	return SourceType
}

func (r Config) Initialize(ctx context.Context, tracer trace.Tracer) (sources.Source, error) {
	pool, err := initMindsDBConnectionPool(ctx, tracer, r.Name, r.Host, r.Port, r.User, r.Password, r.Database, r.QueryTimeout)
	if err != nil {
		return nil, fmt.Errorf("unable to create pool: %w", err)
	}

	err = pool.PingContext(ctx)
	if err != nil {
		pool.Close()
		return nil, fmt.Errorf("unable to connect successfully: %w", err)
	}

	s := &Source{
		Config: r,
		Pool:   pool,
	}
	return s, nil
}

var _ sources.Source = &Source{}

type Source struct {
	Config
	Pool *sql.DB
}

func (s *Source) IsReadOnly() bool {
	return false

View on GitHub (pinned to 8cc6e09de2)

Solutions

Verify user/password with a direct MySQL client against the MindsDB server
Confirm the configured database exists in MindsDB (SHOW DATABASES)
Increase the query timeout / extend the context deadline if pings time out under load
Ensure MindsDB is fully started and reachable before launching the toolbox

Example fix

// before
database: myproj  # not created yet
// after
# run in MindsDB: CREATE DATABASE myproj;
database: myproj

Defensive patterns

Strategy: retry

Validate before calling

db, err := sql.Open("mysql", dsn)
if err != nil { return err }
ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
defer cancel()
if err := db.PingContext(ctx); err != nil {
    return fmt.Errorf("cannot reach mindsdb with given credentials: %w", err)
}

Try / catch

err = pool.PingContext(ctx)
if err != nil {
    if mysqlErr, ok := err.(*mysql.MySQLError); ok && mysqlErr.Number == 1045 {
        // access denied: fix user/password
    }
    // retry with backoff for transient failures
}

Prevention

Create the database/project in MindsDB before wiring the config
Add a readiness check (ping) with backoff at startup for containerized MindsDB
Validate credentials with a mysql CLI one-liner before deploying

When it happens

Trigger: pool.PingContext(ctx) fails because credentials are wrong, the database name is unknown, the server is down/overloaded, or the context deadline (query timeout) expires before the handshake completes.

Common situations: Incorrect MindsDB user/password; database/project name not yet created in MindsDB; MindsDB container not ready at startup; firewall dropping the MySQL-protocol port.

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

AI-assisted analysis of googleapis/mcp-toolbox@8cc6e09de2 (2026-09-05). Data as JSON: /api/errors/ee322aae5e9a4fdf. Report an issue: GitHub.