backup interval should have a minimal value (#13)

pkg/controller/backup-operator/async.go

@@ -32,6 +32,10 @@ func (b *Backup) handle(spec *api.BackupSpec) (*api.BackupStatus, error) {
 func (b *Backup) handleBackupSchedule(spec *api.BackupSpec) {
 	interval := spec.BackupSchedule.BackupIntervalInSecond
 	if interval >= 0 {
+		// we can only support BackupInterval greater than a certain value
+		if interval < minBackupIntervalInSecond {
+			interval = minBackupIntervalInSecond
+		}
 		go func() {
 			if spec.BackupSchedule.MaxBackups == 0 {
 				return

pkg/controller/backup-operator/sync.go

@@ -26,6 +26,8 @@ const (
 	//
 	// 5ms, 10ms, 20ms, 40ms, 80ms, 160ms, 320ms, 640ms, 1.3s, 2.6s, 5.1s, 10.2s, 20.4s, 41s, 82s
 	maxRetries = 15
+	// Minimal backup interval we can use
+	minBackupIntervalInSecond = 60
 )
 
 func (b *Backup) runWorker() {