From d1b6ab46d6974b177309df2ffdec218fc33a6f24 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E5=90=B4=E6=9D=A8=E5=B8=86?=
 <39647285+leno23@users.noreply.github.com>
Date: Sun, 17 May 2026 15:53:16 +0800
Subject: [PATCH] fix: allow resume without download state file

Treat download.state2 as optional for --resume so an existing backup
directory without state can be validated and resumed from scratch.
---
 pkg/backup/download.go      | 18 +++++++++++-------
 pkg/backup/download_test.go | 12 ++++++++++++
 2 files changed, 23 insertions(+), 7 deletions(-)

diff --git a/pkg/backup/download.go b/pkg/backup/download.go
index c469e488..b091f2b4 100644
--- a/pkg/backup/download.go
+++ b/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()
diff --git a/pkg/backup/download_test.go b/pkg/backup/download_test.go
index 27ea7434..ac7c5f7e 100644
--- a/pkg/backup/download_test.go
+++ b/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{