feat(ydbcp): do not call export with empty source paths

cmd/integration/make_backup/main.go

@@ -2,6 +2,8 @@ package main
 
 import (
 	"context"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/status"
 	"log"
 	"time"
 
@@ -45,6 +47,24 @@ func main() {
 	if len(backups.Backups) > 0 {
 		log.Panicf("got backup from empty YDBCP: %s", backups.Backups[0].String())
 	}
+
+	_, err = client.MakeBackup(
+		context.Background(), &pb.MakeBackupRequest{
+			ContainerId:          containerID,
+			DatabaseName:         databaseName,
+			DatabaseEndpoint:     databaseEndpoint,
+			SourcePaths:          nil,
+			SourcePathsToExclude: []string{".+"}, // exclude all paths
+		},
+	)
+	if err == nil {
+		log.Panicf("backup with empty source paths was created")
+	}
+
+	if status.Code(err) != codes.FailedPrecondition {
+		log.Panicf("unexpected error code: %v", err)
+	}
+
 	backupOperation, err := client.MakeBackup(
 		context.Background(), &pb.MakeBackupRequest{
 			ContainerId:          containerID,

internal/backup_operations/make_backup.go

@@ -128,6 +128,11 @@ func MakeBackup(
 		return nil, nil, status.Errorf(codes.Unknown, "error preparing paths for export, dsn %s", dsn)
 	}
 
+	if len(pathsForExport) == 0 {
+		xlog.Error(ctx, "empty list of paths for export")
+		return nil, nil, status.Error(codes.FailedPrecondition, "empty list of paths for export")
+	}
+
 	s3Settings := types.ExportSettings{
 		Endpoint:          s3.Endpoint,
 		Region:            s3.Region,

internal/handlers/schedule_backup_test.go

@@ -26,6 +26,7 @@ func TestBackupScheduleHandler(t *testing.T) {
 		Status:           types.BackupScheduleStateActive,
 		DatabaseName:     "mydb",
 		DatabaseEndpoint: "mydb.valid.com",
+		SourcePaths:      []string{"/path/to/table"},
 		ScheduleSettings: &pb.BackupScheduleSettings{
 			SchedulePattern: &pb.BackupSchedulePattern{Crontab: "* * * * * *"},
 		},

internal/watchers/schedule_watcher/schedule_watcher_test.go

@@ -46,6 +46,7 @@ func TestScheduleWatcherSimple(t *testing.T) {
 		Status:           types.BackupScheduleStateActive,
 		DatabaseName:     "mydb",
 		DatabaseEndpoint: "mydb.valid.com",
+		SourcePaths:      []string{"/path/to/table"},
 		ScheduleSettings: &pb.BackupScheduleSettings{
 			SchedulePattern: &pb.BackupSchedulePattern{Crontab: "* * * * *"}, //every minute
 		},