Add single flight for cache not just origin
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parent
4ecce75e23
commit
45130499cd
2 changed files with 38 additions and 1 deletions
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@ -24,7 +24,7 @@ func NewCachingStore(component string, origin, cache BlobStore) *CachingStore {
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return &CachingStore{
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component: component,
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origin: WithSingleFlight(component, origin),
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cache: cache,
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cache: WithSingleFlight(component, cache),
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}
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}
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@ -80,6 +80,43 @@ func (s *singleflightStore) getter(hash string) func() (interface{}, error) {
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}
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}
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// Put ensures that only one request per hash is sent to the origin at a time,
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// thereby protecting against https://en.wikipedia.org/wiki/Thundering_herd_problem
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func (s *singleflightStore) Put(hash string, blob stream.Blob) error {
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metrics.CacheWaitingRequestsCount.With(metrics.CacheLabels(s.Name(), s.component)).Inc()
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defer metrics.CacheWaitingRequestsCount.With(metrics.CacheLabels(s.Name(), s.component)).Dec()
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_, err, _ := s.sf.Do(hash, s.putter(hash, blob))
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if err != nil {
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return err
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}
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return nil
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}
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// putter returns a function that puts a blob from the origin
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// only one putter per hash will be executing at a time
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func (s *singleflightStore) putter(hash string, blob stream.Blob) func() (interface{}, error) {
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return func() (interface{}, error) {
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metrics.CacheOriginRequestsCount.With(metrics.CacheLabels(s.Name(), s.component)).Inc()
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defer metrics.CacheOriginRequestsCount.With(metrics.CacheLabels(s.Name(), s.component)).Dec()
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start := time.Now()
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err := s.BlobStore.Put(hash, blob)
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if err != nil {
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return nil, err
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}
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rate := float64(len(blob)) / 1024 / 1024 / time.Since(start).Seconds()
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metrics.CacheRetrievalSpeed.With(map[string]string{
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metrics.LabelCacheType: s.Name(),
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metrics.LabelComponent: s.component,
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metrics.LabelSource: "origin",
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}).Set(rate)
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return nil, nil
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}
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}
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// Shutdown shuts down the store gracefully
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func (s *singleflightStore) Shutdown() {
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s.BlobStore.Shutdown()
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