fix: allow resume without download state file

pkg/backup/download.go

@@ -40,6 +40,16 @@ var (
 	ErrBackupIsAlreadyExists = errors.New("backup is already exists")
 )
 
+func (b *Backuper) resumeExistingBackup(backupName string) bool {
+	_, checkDownloadErr := os.Stat(path.Join(b.DefaultDataPath, "backup", backupName, "download.state2"))
+	if errors.Is(checkDownloadErr, os.ErrNotExist) {
+		log.Warn().Msgf("%s already exists but no download.state2 found, will resume download from scratch", backupName)
+	} else {
+		log.Warn().Msgf("%s already exists will try to resume download", backupName)
+	}
+	return true
+}
+
 func (b *Backuper) Download(backupName string, tablePattern string, partitions []string, schemaOnly, rbacOnly, configsOnly, namedCollectionsOnly, resume bool, hardlinkExistsFiles bool, backupVersion string, commandId int) error {
 	if pidCheckErr := pidlock.CheckAndCreatePidFile(backupName, "download"); pidCheckErr != nil {
 		return errors.WithMessage(pidCheckErr, "CheckAndCreatePidFile")
@@ -87,14 +97,8 @@ func (b *Backuper) Download(backupName string, tablePattern string, partitions [
 			}
 			if !b.resume {
 				return ErrBackupIsAlreadyExists
-			} else {
-				_, checkDownloadErr := os.Stat(path.Join(b.DefaultDataPath, "backup", backupName, "download.state2"))
-				if errors.Is(checkDownloadErr, os.ErrNotExist) {
-					return ErrBackupIsAlreadyExists
-				}
-				isResumeExists = true
-				log.Warn().Msgf("%s already exists will try to resume download", backupName)
 			}
+			isResumeExists = b.resumeExistingBackup(backupName)
 		}
 	}
 	startDownload := time.Now()

pkg/backup/download_test.go

@@ -1,6 +1,8 @@
 package backup
 
 import (
+	"os"
+	"path"
 	"regexp"
 	"testing"
 	"time"
@@ -91,6 +93,16 @@ var remoteBackup = storage.Backup{
 	UploadDate: time.Now(),
 }
 
+func TestResumeExistingBackupAllowsMissingStateFile(t *testing.T) {
+	backupName := "test_resume_crash"
+	defaultDataPath := t.TempDir()
+	assert.NoError(t, os.MkdirAll(path.Join(defaultDataPath, "backup", backupName), 0o750))
+
+	backuper := &Backuper{DefaultDataPath: defaultDataPath}
+
+	assert.True(t, backuper.resumeExistingBackup(backupName))
+}
+
 func TestReBalanceTablesMetadataIfDiskNotExists_Files_NoErrors(t *testing.T) {
 	remoteBackup.DataFormat = "tar"
 	baseTable := metadata.TableMetadata{