diff --git a/pkg/storage/cacher/watch_cache.go b/pkg/storage/cacher/watch_cache.go index 783cf4524..4d86018e5 100644 --- a/pkg/storage/cacher/watch_cache.go +++ b/pkg/storage/cacher/watch_cache.go @@ -156,14 +156,15 @@ type watchCache struct { // getAttrsFunc is used to get labels and fields of an object. getAttrsFunc func(runtime.Object) (labels.Set, fields.Set, error) - // cache is used a cyclic buffer - its first element (with the smallest - // resourceVersion) is defined by startIndex, its last element is defined - // by endIndex (if cache is full it will be startIndex + capacity). - // Both startIndex and endIndex can be greater than buffer capacity - - // you should always apply modulo capacity to get an index in cache array. + // cache is used a cyclic buffer - the "current" contents of it are + // stored in [start_index%capacity, end_index%capacity) - so the + // "current" contents have exactly end_index-start_index items. cache []*watchCacheEvent startIndex int endIndex int + // removedEventSinceRelist holds the information whether any of the events + // were already removed from the `cache` cyclic buffer since the last relist + removedEventSinceRelist bool // store will effectively support LIST operation from the "end of cache // history" i.e. from the moment just after the newest cached watched event. @@ -346,6 +347,7 @@ func (w *watchCache) updateCache(event *watchCacheEvent) { if w.isCacheFullLocked() { // Cache is full - remove the oldest element. w.startIndex++ + w.removedEventSinceRelist = true } w.cache[w.endIndex%w.capacity] = event w.endIndex++ @@ -572,8 +574,15 @@ func (w *watchCache) Replace(objs []interface{}, resourceVersion string) error { w.Lock() defer w.Unlock() - w.startIndex = 0 - w.endIndex = 0 + // Ensure startIndex never decreases, so that existing watchCacheInterval + // instances get "invalid" errors if the try to download from the buffer + // using their own start/end indexes calculated from previous buffer + // content. + + // Empty the cyclic buffer, ensuring startIndex doesn't decrease. + w.startIndex = w.endIndex + w.removedEventSinceRelist = false + if err := w.store.Replace(toReplace, resourceVersion); err != nil { return err } @@ -664,7 +673,7 @@ func (w *watchCache) getAllEventsSinceLocked(resourceVersion uint64) (*watchCach size := w.endIndex - w.startIndex var oldest uint64 switch { - case w.listResourceVersion > 0 && w.startIndex == 0: + case w.listResourceVersion > 0 && !w.removedEventSinceRelist: // If no event was removed from the buffer since last relist, the oldest watch // event we can deliver is one greater than the resource version of the list. oldest = w.listResourceVersion + 1