Basic server app with WS connection.

server/internal/services/core/database/connection.go

@@ -0,0 +1,83 @@
+package database
+
+import (
+	"errors"
+	"fmt"
+	"net/url"
+	"os"
+	"strconv"
+	"strings"
+
+	"github.com/jmoiron/sqlx"
+	// postgresql driver.
+	_ "github.com/jackc/pgx/v5/stdlib"
+)
+
+const (
+	databaseDSNEnvVar            = "BUNKERD_DATABASE_DSN"
+	databaseMaxIdleConnsEnvVar   = "BUNKERD_DATABASE_MAX_IDLE_CONNS"
+	databaseMaxOpenedConnsEnvVar = "BUNKERD_DATABASE_MAX_OPENED_CONNS"
+)
+
+var (
+	errDSNInvalid            = errors.New("BUNKERD_DATABASE_DSN environment variable is empty or invalid")
+	errNoMaxIdleConns        = errors.New("no BUNKERD_DATABASE_MAX_IDLE_CONNS defined")
+	errNoMaxOpenedConns      = errors.New("no BUNKERD_DATABASE_MAX_OPENED_CONNS defined")
+	errPostgresOnlySupported = errors.New("only PostgreSQL database is currently supported")
+)
+
+func (d *database) initializeConnection() error {
+	// Getting database DSN from environment as well as other required settings.
+	dsn, found := os.LookupEnv(databaseDSNEnvVar)
+	if !found {
+		return fmt.Errorf("initialize connection: getting database DSN: %w", errDSNInvalid)
+	}
+
+	maxOpenedConnsRaw, found := os.LookupEnv(databaseMaxOpenedConnsEnvVar)
+	if !found {
+		return fmt.Errorf("initialize connection: getting maximum number of opened conections: %w", errNoMaxOpenedConns)
+	}
+
+	maxOpenedConns, err := strconv.ParseInt(maxOpenedConnsRaw, 10, 64)
+	if err != nil {
+		return fmt.Errorf("initialize connection: parsing maximum number of opened conections: %w", err)
+	}
+
+	maxIdleConnsRaw, found := os.LookupEnv(databaseMaxIdleConnsEnvVar)
+	if !found {
+		return fmt.Errorf("initialize connection: getting maximum number of idle conections: %w", errNoMaxIdleConns)
+	}
+
+	maxIdleConns, err := strconv.ParseInt(maxIdleConnsRaw, 10, 64)
+	if err != nil {
+		return fmt.Errorf("initialize connection: parsing maximum number of opened conections: %w", err)
+	}
+
+	// While database/sql (and sqlx) supports all possible DSN formats, we will force user to use DSN in form
+	// "proto://user:passowrd@host:port/dbname" as it is easier to parse.
+	if _, err := url.Parse(dsn); err != nil {
+		return fmt.Errorf("initialize connection: validate DSN: %w", err)
+	}
+
+	// Currently we're support only postgresql, but this may change in future.
+	if !strings.HasPrefix(dsn, "postgres://") {
+		return fmt.Errorf("initialize connection: validate DSN: %w", errPostgresOnlySupported)
+	}
+
+	proto := strings.Split(dsn, ":")[0]
+	if proto == "postgres" {
+		proto = "pgx"
+	}
+
+	db, err := sqlx.Open(proto, dsn)
+	if err != nil {
+		return fmt.Errorf("initialize connection: open database: %w", err)
+	}
+
+	d.db = db
+
+	d.db.SetMaxOpenConns(int(maxOpenedConns))
+	d.db.SetMaxIdleConns(int(maxIdleConns))
+
+	return nil
+}