Cleanup and document hacky sql interaction

internal/component/sql/connect.go

@@ -0,0 +1,139 @@
+package sql
+
+import (
+	"context"
+	"database/sql"
+	"fmt"
+	"net"
+	"sync/atomic"
+
+	mysqldriver "github.com/go-sql-driver/mysql"
+
+	"gorm.io/driver/mysql"
+	"gorm.io/gorm"
+	"gorm.io/gorm/logger"
+
+	"github.com/FAU-CDI/wisski-distillery/internal/models"
+	"github.com/FAU-CDI/wisski-distillery/pkg/wait"
+)
+
+//
+// ========== low-level connection ==========
+//
+
+// Query performs a database query, outside a database contect
+func (sql *SQL) Query(query string, args ...interface{}) error {
+	// connect to the server
+	conn, err := sql.connect("")
+	if err != nil {
+		return err
+	}
+
+	// do the query!
+	{
+		_, err := conn.Exec(query, args...)
+		if err != nil {
+			return err
+		}
+		return nil
+	}
+}
+
+// WaitQuery waits for the query interface to be able to connect to the database
+func (sql *SQL) WaitQuery() error {
+	return wait.Wait(func() bool {
+		err := sql.Query("select 1;")
+		// log.Printf("[WaitQuery] %s\n", err) // debug
+		return err == nil
+	}, sql.PollInterval, sql.PollContext)
+}
+
+//
+// ========== connection via gorm ==========
+//
+
+// QueryTable returns a gorm.DB to connect to the provided gorm database table
+func (sql *SQL) QueryTable(silent bool, name string) (*gorm.DB, error) {
+	conn, err := sql.connect(sql.Config.DistilleryDatabase)
+	if err != nil {
+		return nil, err
+	}
+
+	// gorm configuration
+	config := &gorm.Config{}
+	if silent {
+		config.Logger = logger.Default.LogMode(logger.Silent)
+	}
+
+	// mysql connection
+	cfg := mysql.Config{
+		Conn: conn,
+
+		DefaultStringSize: 256,
+	}
+
+	// open the gorm connection!
+	db, err := gorm.Open(mysql.New(cfg), config)
+	if err != nil {
+		return nil, err
+	}
+
+	// set the table
+	db = db.Table(name)
+
+	// check that nothing went wrong
+	if db.Error != nil {
+		return nil, db.Error
+	}
+	return db, nil
+}
+
+// WaitQueryTable waits for a connection to succeed via QueryTable
+func (sql *SQL) WaitQueryTable() error {
+	return wait.Wait(func() bool {
+		_, err := sql.QueryTable(true, models.InstanceTable)
+		return err == nil
+	}, sql.PollInterval, sql.PollContext)
+}
+
+//
+// ========== low-level database connection ==========
+//
+
+func (ssql *SQL) connect(database string) (*sql.DB, error) {
+	conn, err := sql.Open("mysql", ssql.dsn(database))
+	if err != nil {
+		return nil, err
+	}
+
+	conn.SetMaxIdleConns(0)
+
+	return conn, nil
+}
+
+// dsn returns a dsn fof connecting to the database
+func (sql *SQL) dsn(database string) string {
+	user := sql.Config.MysqlAdminUser
+	pass := sql.Config.MysqlAdminPassword
+	network := sql.network()
+	server := sql.ServerURL
+
+	return fmt.Sprintf("%s:%s@%s(%s)/%s?charset=utf8&parseTime=True&loc=Local", user, pass, network, server, database)
+}
+
+var proxyNameCounter uint64
+
+// network returns the network to use to connect to the database
+func (sql *SQL) network() string {
+	return sql.lazyNetwork.Get(func() (name string) {
+		network := "tcp"
+
+		// register a new DialContext function to use the environment.
+		// this seems like a bit of a hack, but it works for now.
+		name = fmt.Sprintf("sql-network-%d", atomic.AddUint64(&proxyNameCounter, 1))
+		mysqldriver.RegisterDialContext(name, func(ctx context.Context, addr string) (net.Conn, error) {
+			return sql.Core.Environment.DialContext(ctx, network, addr)
+		})
+		return
+	})
+}