check.go

package sqlserver

import (
	"context"
	"database/sql"
	"fmt"

	"github.com/microsoft/go-mssqldb/azuread"
)

// Config is the SQL Server checker configuration settings container.
type Config struct {
	// DSN is the SQL Server instance connection DSN. Required.
	DSN string
}

// New creates new SQL Server health check that verifies the following:
// - connection establishing
// - doing the ping command
// - selecting SQL Server version
func New(config Config) func(ctx context.Context) error {
	return func(ctx context.Context) (checkErr error) {
		db, err := sql.Open(azuread.DriverName, config.DSN)
		if err != nil {
			checkErr = fmt.Errorf("SQL Server health check failed on connect: %w", err)
			return
		}

		defer func() {
			// override checkErr only if there were no other errors
			if err = db.Close(); err != nil && checkErr == nil {
				checkErr = fmt.Errorf("SQL Server health check failed on connection closing: %w", err)
			}
		}()

		err = db.PingContext(ctx)
		if err != nil {
			checkErr = fmt.Errorf("SQL Server health check failed on ping: %w", err)
			return
		}

		rows, err := db.QueryContext(ctx, `SELECT @@VERSION`)
		if err != nil {
			checkErr = fmt.Errorf("SQL Server health check failed on select: %w", err)
			return
		}
		if err = rows.Close(); err != nil {
			checkErr = fmt.Errorf("SQL Server health check failed on rows closing: %w", err)
		}

		return
	}
}