Automatic pre-migration DB backups

common.go

@@ -30,7 +30,7 @@ type UserError struct {
 	Err  error
 }
 
-func (e *UserError) Error() string {
+func (e UserError) Error() string {
 	return e.Err.Error()
 }
 

config.go

@@ -81,6 +81,7 @@ type Config struct {
 	ListenAddress              string
 	LogRequests                bool
 	MinPasswordLength          int
+	PreMigrationBackups        bool
 	RateLimit                  rateLimitConfig
 	RegistrationExistingPlayer registrationExistingPlayerConfig
 	RegistrationNewPlayer      registrationNewPlayerConfig
@@ -128,6 +129,7 @@ func DefaultConfig() Config {
 		LogRequests:              true,
 		MinPasswordLength:        8,
 		OfflineSkins:             true,
+		PreMigrationBackups:      true,
 		RateLimit:                defaultRateLimitConfig,
 		RegistrationExistingPlayer: registrationExistingPlayerConfig{
 			Allow: false,

db.go

@@ -5,12 +5,14 @@ import (
 	"errors"
 	"fmt"
 	mapset "github.com/deckarep/golang-set/v2"
+	"github.com/samber/mo"
 	"gorm.io/driver/sqlite"
 	"gorm.io/gorm"
 	"gorm.io/gorm/logger"
 	"log"
 	"os"
 	"path"
+	"path/filepath"
 	"time"
 )
 
@@ -47,6 +49,14 @@ func IsErrorPlayerNameTakenByUsername(err error) bool {
 	return err.Error() == PLAYER_NAME_TAKEN_BY_USERNAME_ERROR
 }
 
+type BackwardsMigrationError struct {
+	Err error
+}
+
+func (e BackwardsMigrationError) Error() string {
+	return e.Err.Error()
+}
+
 type V1User struct {
 	IsAdmin           bool
 	IsLocked          bool
@@ -137,7 +147,7 @@ func OpenDB(config *Config) (*gorm.DB, error) {
 	db := Unwrap(gorm.Open(sqlite.Open(dbPath), &gorm.Config{
 		Logger: logger.Default.LogMode(logger.Silent),
 	}))
-	err = Migrate(config, db, alreadyExisted, CURRENT_USER_VERSION)
+	err = Migrate(config, mo.Some(dbPath), db, alreadyExisted, CURRENT_USER_VERSION)
 	if err != nil {
 		return nil, fmt.Errorf("Error migrating database: %w", err)
 	}
@@ -150,7 +160,7 @@ func setUserVersion(tx *gorm.DB, userVersion uint) error {
 	return tx.Exec(fmt.Sprintf("PRAGMA user_version = %d", userVersion)).Error
 }
 
-func Migrate(config *Config, db *gorm.DB, alreadyExisted bool, targetUserVersion uint) error {
+func Migrate(config *Config, dbPath mo.Option[string], db *gorm.DB, alreadyExisted bool, targetUserVersion uint) error {
 	var userVersion uint
 
 	if alreadyExisted {
@@ -162,10 +172,29 @@ func Migrate(config *Config, db *gorm.DB, alreadyExisted bool, targetUserVersion
 	}
 
 	initialUserVersion := userVersion
+	if initialUserVersion > targetUserVersion {
+		return BackwardsMigrationError{
+			Err: fmt.Errorf("Database is version %d, migration target version is %d, cannot continue. Are you trying to run an older version of %s with a newer database?", userVersion, targetUserVersion, config.ApplicationName),
+		}
+	}
+
 	if initialUserVersion < targetUserVersion {
-		log.Printf("Started migration of database version %d to %d", userVersion, targetUserVersion)
+		log.Printf("Started migration of database version %d to %d.", userVersion, targetUserVersion)
-	} else if initialUserVersion > targetUserVersion {
+		if !config.PreMigrationBackups {
-		return fmt.Errorf("Database is version %d, migration target version is %d, cannot continue. Are you trying to run an older version of %s with a newer database?", userVersion, targetUserVersion, config.ApplicationName)
+			log.Printf("PreMigrationBackups disabled, skipping backup.")
+		} else if p, ok := dbPath.Get(); ok {
+			dbDir := filepath.Dir(p)
+			datetime := time.Now().UTC().Format("2006-01-02T15-04-05Z")
+			backupPath := path.Join(dbDir, fmt.Sprintf("drasl.%d.%s.db", userVersion, datetime))
+			log.Printf("Backing up old database to %s", backupPath)
+			_, err := CopyPath(p, backupPath)
+			if err != nil {
+				return fmt.Errorf("Error backing up database: %w", err)
+			}
+			log.Printf("Database backed up, proceeding.")
+		} else {
+			log.Printf("Database path not specified, skipping backup.")
+		}
 	}
 
 	err := db.Transaction(func(tx *gorm.DB) error {

db_test.go

@@ -1,6 +1,8 @@
 package main
 
 import (
+	"errors"
+	"github.com/samber/mo"
 	"github.com/stretchr/testify/assert"
 	"gorm.io/driver/sqlite"
 	"gorm.io/gorm"
@@ -8,16 +10,11 @@ import (
 	"io"
 	"log"
 	"os"
-	"path"
 	"testing"
 )
 
 func (ts *TestSuite) getFreshDatabase(t *testing.T) *gorm.DB {
-	dbPath := path.Join(ts.Config.StateDirectory, "drasl.db")
+	db, err := gorm.Open(sqlite.Open(":memory:"), &gorm.Config{
-	if err := os.Remove(dbPath); err != nil {
-		assert.True(t, os.IsNotExist(err))
-	}
-	db, err := gorm.Open(sqlite.Open(dbPath), &gorm.Config{
 		Logger: logger.Default.LogMode(logger.Silent),
 	})
 	assert.Nil(t, err)
@@ -45,11 +42,12 @@ func TestDB(t *testing.T) {
 	t.Run("Test 2->3 migration", ts.testMigrate2To3)
 	t.Run("Test 3->4 migration", ts.testMigrate3To4)
 	t.Run("Test 3->4 migration, username/player name collision", ts.testMigrate3To4Collision)
+	t.Run("Test backwards migration", ts.testMigrateBackwards)
 }
 
 func (ts *TestSuite) testFreshDatabase(t *testing.T) {
 	db := ts.getFreshDatabase(t)
-	err := Migrate(ts.Config, db, false, CURRENT_USER_VERSION)
+	err := Migrate(ts.Config, mo.None[string](), db, false, CURRENT_USER_VERSION)
 	assert.Nil(t, err)
 }
 
@@ -63,7 +61,7 @@ func (ts *TestSuite) testMigrate1To2(t *testing.T) {
 	var v1Client V1Client
 	assert.Nil(t, db.First(&v1Client).Error)
 
-	err = Migrate(ts.Config, db, true, 2)
+	err = Migrate(ts.Config, mo.None[string](), db, true, 2)
 	assert.Nil(t, err)
 
 	var v2Client V2Client
@@ -83,7 +81,7 @@ func (ts *TestSuite) testMigrate2To3(t *testing.T) {
 	var v2User V2User
 	assert.Nil(t, db.First(&v2User).Error)
 
-	err = Migrate(ts.Config, db, true, 3)
+	err = Migrate(ts.Config, mo.None[string](), db, true, 3)
 	assert.Nil(t, err)
 
 	var v3User V3User
@@ -101,7 +99,7 @@ func (ts *TestSuite) testMigrate3To4(t *testing.T) {
 	var v3User V3User
 	assert.Nil(t, db.First(&v3User).Error)
 
-	err = Migrate(ts.Config, db, true, 4)
+	err = Migrate(ts.Config, mo.None[string](), db, true, 4)
 	assert.Nil(t, err)
 
 	var v4User V4User
@@ -133,7 +131,7 @@ func (ts *TestSuite) testMigrate3To4Collision(t *testing.T) {
 	assert.Nil(t, db.First(&v3qux, "username = ?", "qux").Error)
 	assert.Equal(t, "foo", v3qux.PlayerName)
 
-	err = Migrate(ts.Config, db, true, 4)
+	err = Migrate(ts.Config, mo.None[string](), db, true, 4)
 	assert.Nil(t, err)
 
 	var v4foo V4User
@@ -146,3 +144,16 @@ func (ts *TestSuite) testMigrate3To4Collision(t *testing.T) {
 	assert.Equal(t, 1, len(v4qux.Players))
 	assert.Equal(t, "qux", v4qux.Players[0].Name)
 }
+
+func (ts *TestSuite) testMigrateBackwards(t *testing.T) {
+	db := ts.getFreshDatabase(t)
+
+	query, err := os.ReadFile("sql/1.sql")
+	assert.Nil(t, err)
+	assert.Nil(t, db.Exec(string(query)).Error)
+	setUserVersion(db, CURRENT_USER_VERSION+1)
+
+	err = Migrate(ts.Config, mo.None[string](), db, true, CURRENT_USER_VERSION)
+	var backwardsMigrationError BackwardsMigrationError
+	assert.True(t, errors.As(err, &backwardsMigrationError))
+}

doc/configuration.md

@@ -20,6 +20,7 @@ Other available options:
 - `ListenAddress`: IP address and port to listen on. Depending on how you configure your reverse proxy and whether you run Drasl in a container, you should consider setting the listen address to `"127.0.0.1:25585"` to ensure Drasl is only accessible through the reverse proxy. If your reverse proxy is unable to connect to Drasl, try setting this back to the default value. String. Default value: `"0.0.0.0:25585"`.
 - `DefaultAdmins`: Usernames of the instance's permanent admins. Admin rights can be granted to other accounts using the web UI, but admins defined via `DefaultAdmins` cannot be demoted unless they are removed from the config file. Array of strings. Default value: `[]`.
 - `DefaultMaxPlayerCount`: Number of players each user is allowed to own by default. Admins can increase or decrease each user's individual limit. Use `-1` to allow creating an unlimited number of players. Integer. Default value: `1`.
+- `PreMigrationBackups`: Back up the database to `/path/to/StateDirectory/drasl.X.YYYY-mm-ddTHH-MM-SSZ.db` (where `X` is the old database version) before migrating to a new database version. Boolean. Default value: `true`.
 - `EnableBackgroundEffect`: Whether to enable the 3D background animation in the web UI. Boolean. Default value: `true`.
 - `EnableFooter`: Whether to enable the page footer in the web UI. Boolean. Default value: `true`.
 - `[RateLimit]`: Rate-limit requests per IP address to limit abuse. Only applies to certain web UI routes, not any Yggdrasil routes. Requests for skins, capes, and web pages are also unaffected. Uses [Echo](https://echo.labstack.com)'s [rate limiter middleware](https://echo.labstack.com/middleware/rate-limiter/).

util.go

@@ -8,7 +8,9 @@ import (
 	"crypto/sha256"
 	"encoding/hex"
 	"github.com/jxskiss/base62"
+	"io"
 	"log"
+	"os"
 	"strings"
 	"sync"
 )
@@ -141,3 +143,23 @@ func (m *KeyedMutex) Lock(key string) func() {
 
 	return func() { mtx.Unlock() }
 }
+
+func CopyPath(sourcePath string, destinationPath string) (int64, error) {
+	source, err := os.Open(sourcePath)
+	if err != nil {
+		return 0, err
+	}
+	defer source.Close()
+
+	destination, err := os.Create(destinationPath)
+	if err != nil {
+		return 0, err
+	}
+	defer destination.Close()
+
+	bytesWritten, err := io.Copy(destination, source)
+	if err != nil {
+		return 0, err
+	}
+	return bytesWritten, nil
+}