y/watermark.go
func (w *WaterMark) Begin(index uint64) {
	atomic.StoreUint64(&w.lastIndex, index)
	w.markCh <- mark{index: index, done: false}
}
func (w *WaterMark) Begin(index uint64) {
	atomic.StoreUint64(&w.lastIndex, index)
	w.markCh <- mark{index: index, done: false}
}
func ( w * WaterMark ) Begin ( index uint64 ) { atomic . StoreUint64 ( & w . lastIndex , index ) w . markCh <- mark { index : index , done : false } }
// Begin sets the last index to the given value.
Begin sets the last index to the given value .