Smarter caches #46
8 changed files with 126 additions and 59 deletions
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@ -29,6 +29,7 @@ func getStreamCmd(cmd *cobra.Command, args []string) {
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sdHash := args[1]
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s := store.NewCachingStore(
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"getstream",
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peer.NewStore(peer.StoreOpts{Address: addr}),
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store.NewDiskStore("/tmp/lbry_downloaded_blobs", 2),
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)
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@ -153,13 +153,19 @@ func wrapWithCache(s store.BlobStore) store.BlobStore {
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if err != nil {
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log.Fatal(err)
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}
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wrapped = store.NewCachingStore(wrapped,
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store.NewLRUStore(store.NewDiskStore(diskCachePath, 2), diskCacheMaxSize))
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wrapped = store.NewCachingStore(
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"reflector",
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wrapped,
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store.NewLRUStore("peer_server", store.NewDiskStore(diskCachePath, 2), diskCacheMaxSize),
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)
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}
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if reflectorCmdMemCache > 0 {
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wrapped = store.NewCachingStore(wrapped,
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store.NewLRUStore(store.NewMemStore(), reflectorCmdMemCache))
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wrapped = store.NewCachingStore(
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"reflector",
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wrapped,
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store.NewLRUStore("peer_server", store.NewMemStore(), reflectorCmdMemCache),
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)
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}
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return wrapped
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@ -12,6 +12,7 @@ import (
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ee "github.com/lbryio/lbry.go/v2/extras/errors"
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"github.com/lbryio/lbry.go/v2/extras/stop"
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"github.com/prometheus/client_golang/prometheus"
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"github.com/prometheus/client_golang/prometheus/promauto"
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"github.com/prometheus/client_golang/prometheus/promhttp"
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@ -67,6 +68,7 @@ const (
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DirectionDownload = "download" // from reflector
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LabelCacheType = "cache_type"
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LabelComponent = "component"
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LabelSource = "source"
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errConnReset = "conn_reset"
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@ -116,37 +118,42 @@ var (
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Help: "Total number of blobs downloaded from reflector through QUIC protocol",
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})
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CacheHitCount = promauto.NewCounter(prometheus.CounterOpts{
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CacheHitCount = promauto.NewCounterVec(prometheus.CounterOpts{
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Namespace: ns,
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Subsystem: subsystemCache,
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Name: "hit_total",
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Help: "Total number of blobs retrieved from the cache storage",
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})
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CacheMissCount = promauto.NewCounter(prometheus.CounterOpts{
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}, []string{LabelCacheType, LabelComponent})
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CacheMissCount = promauto.NewCounterVec(prometheus.CounterOpts{
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Namespace: ns,
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Subsystem: subsystemCache,
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Name: "miss_total",
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Help: "Total number of blobs retrieved from origin rather than cache storage",
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})
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CacheOriginRequestsCount = promauto.NewGauge(prometheus.GaugeOpts{
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}, []string{LabelCacheType, LabelComponent})
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CacheOriginRequestsCount = promauto.NewGaugeVec(prometheus.GaugeOpts{
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Namespace: ns,
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Subsystem: subsystemCache,
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Name: "origin_requests_total",
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Help: "How many Get requests are in flight from the cache to the origin",
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})
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}, []string{LabelCacheType, LabelComponent})
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// during thundering-herd situations, the metric below should be a lot smaller than the metric above
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CacheWaitingRequestsCount = promauto.NewGauge(prometheus.GaugeOpts{
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CacheWaitingRequestsCount = promauto.NewGaugeVec(prometheus.GaugeOpts{
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Namespace: ns,
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Subsystem: subsystemCache,
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Name: "waiting_requests_total",
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Help: "How many cache requests are waiting for an in-flight origin request",
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})
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}, []string{LabelCacheType, LabelComponent})
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CacheLRUEvictCount = promauto.NewCounterVec(prometheus.CounterOpts{
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Namespace: ns,
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Subsystem: subsystemCache,
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Name: "evict_total",
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Help: "Count of blobs evicted from cache",
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}, []string{LabelCacheType})
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}, []string{LabelCacheType, LabelComponent})
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CacheRetrievalSpeed = promauto.NewGaugeVec(prometheus.GaugeOpts{
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Namespace: ns,
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Name: "speed_mbps",
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Help: "Speed of blob retrieval from cache or from origin",
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}, []string{LabelCacheType, LabelComponent, LabelSource})
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BlobUploadCount = promauto.NewCounter(prometheus.CounterOpts{
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Namespace: ns,
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@ -159,12 +166,6 @@ var (
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Help: "Total number of SD blobs (and therefore streams) uploaded to reflector",
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})
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RetrieverSpeed = promauto.NewGaugeVec(prometheus.GaugeOpts{
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Namespace: ns,
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Name: "speed_mbps",
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Help: "Speed of blob retrieval",
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}, []string{LabelSource})
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MtrInBytesTcp = promauto.NewCounter(prometheus.CounterOpts{
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Namespace: ns,
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Name: "tcp_in_bytes",
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@ -202,6 +203,13 @@ var (
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})
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)
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func CacheLabels(name, component string) prometheus.Labels {
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return prometheus.Labels{
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LabelCacheType: name,
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LabelComponent: component,
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}
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}
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func TrackError(direction string, e error) (shouldLog bool) { // shouldLog is a hack, but whatever
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if e == nil {
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return
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@ -7,8 +7,6 @@ import (
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"github.com/lbryio/lbry.go/v2/stream"
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"github.com/lbryio/reflector.go/internal/metrics"
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"golang.org/x/sync/singleflight"
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)
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// CachingStore combines two stores, typically a local and a remote store, to improve performance.
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@ -16,13 +14,16 @@ import (
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// are retrieved from the origin and cached. Puts are cached and also forwarded to the origin.
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type CachingStore struct {
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origin, cache BlobStore
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sf *singleflight.Group
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component string
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}
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// NewCachingStore makes a new caching disk store and returns a pointer to it.
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func NewCachingStore(origin, cache BlobStore) *CachingStore {
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return &CachingStore{origin: origin, cache: cache, sf: new(singleflight.Group)}
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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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}
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}
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const nameCaching = "caching"
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@ -45,41 +46,25 @@ func (c *CachingStore) Get(hash string) (stream.Blob, error) {
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start := time.Now()
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blob, err := c.cache.Get(hash)
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if err == nil || !errors.Is(err, ErrBlobNotFound) {
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metrics.CacheHitCount.Inc()
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metrics.CacheHitCount.With(metrics.CacheLabels(c.cache.Name(), c.component)).Inc()
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rate := float64(len(blob)) / 1024 / 1024 / time.Since(start).Seconds()
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metrics.RetrieverSpeed.With(map[string]string{metrics.LabelSource: "cache"}).Set(rate)
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metrics.CacheRetrievalSpeed.With(map[string]string{
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metrics.LabelCacheType: c.cache.Name(),
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metrics.LabelComponent: c.component,
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metrics.LabelSource: "cache",
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}).Set(rate)
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return blob, err
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}
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metrics.CacheMissCount.Inc()
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return c.getFromOrigin(hash)
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}
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metrics.CacheMissCount.With(metrics.CacheLabels(c.cache.Name(), c.component)).Inc()
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// getFromOrigin ensures that only one Get 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 (c *CachingStore) getFromOrigin(hash string) (stream.Blob, error) {
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metrics.CacheWaitingRequestsCount.Inc()
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defer metrics.CacheWaitingRequestsCount.Dec()
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originBlob, err, _ := c.sf.Do(hash, func() (interface{}, error) {
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metrics.CacheOriginRequestsCount.Inc()
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defer metrics.CacheOriginRequestsCount.Dec()
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start := time.Now()
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blob, err := c.origin.Get(hash)
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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.RetrieverSpeed.With(map[string]string{metrics.LabelSource: "origin"}).Set(rate)
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err = c.cache.Put(hash, blob)
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return blob, err
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})
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blob, err = c.origin.Get(hash)
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if err != nil {
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return nil, err
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}
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return originBlob.(stream.Blob), nil
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err = c.cache.Put(hash, blob)
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return blob, err
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}
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// Put stores the blob in the origin and the cache
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@ -12,7 +12,7 @@ import (
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func TestCachingStore_Put(t *testing.T) {
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origin := NewMemStore()
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cache := NewMemStore()
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s := NewCachingStore(origin, cache)
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s := NewCachingStore("test", origin, cache)
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b := []byte("this is a blob of stuff")
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hash := "hash"
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@ -42,7 +42,7 @@ func TestCachingStore_Put(t *testing.T) {
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func TestCachingStore_CacheMiss(t *testing.T) {
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origin := NewMemStore()
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cache := NewMemStore()
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s := NewCachingStore(origin, cache)
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s := NewCachingStore("test", origin, cache)
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b := []byte("this is a blob of stuff")
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hash := "hash"
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@ -80,7 +80,7 @@ func TestCachingStore_ThunderingHerd(t *testing.T) {
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storeDelay := 100 * time.Millisecond
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origin := NewSlowBlobStore(storeDelay)
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cache := NewMemStore()
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s := NewCachingStore(origin, cache)
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s := NewCachingStore("test", origin, cache)
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b := []byte("this is a blob of stuff")
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hash := "hash"
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@ -17,9 +17,9 @@ type LRUStore struct {
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}
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// NewLRUStore initialize a new LRUStore
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func NewLRUStore(store BlobStore, maxItems int) *LRUStore {
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func NewLRUStore(component string, store BlobStore, maxItems int) *LRUStore {
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lru, err := golru.NewWithEvict(maxItems, func(key interface{}, value interface{}) {
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metrics.CacheLRUEvictCount.WithLabelValues(store.Name()).Inc()
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metrics.CacheLRUEvictCount.With(metrics.CacheLabels(store.Name(), component)).Inc()
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_ = store.Delete(key.(string)) // TODO: log this error. may happen if underlying entry is gone but cache entry still there
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})
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if err != nil {
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@ -17,7 +17,7 @@ const cacheMaxBlobs = 3
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func getTestLRUStore() (*LRUStore, *DiskStore) {
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d := NewDiskStore("/", 2)
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d.fs = afero.NewMemMapFs()
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return NewLRUStore(d, 3), d
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return NewLRUStore("test", d, 3), d
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}
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func countOnDisk(t *testing.T, disk *DiskStore) int {
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@ -134,7 +134,7 @@ func TestLRUStore_loadExisting(t *testing.T) {
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require.Equal(t, 1, len(existing), "blob should exist in cache")
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assert.Equal(t, hash, existing[0])
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lru := NewLRUStore(d, 3) // lru should load existing blobs when it's created
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lru := NewLRUStore("test", d, 3) // lru should load existing blobs when it's created
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has, err := lru.Has(hash)
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require.NoError(t, err)
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assert.True(t, has, "hash should be loaded from disk store but it's not")
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67
store/singleflight.go
Normal file
67
store/singleflight.go
Normal file
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@ -0,0 +1,67 @@
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package store
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import (
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"time"
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"github.com/lbryio/reflector.go/internal/metrics"
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"github.com/lbryio/lbry.go/v2/stream"
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"golang.org/x/sync/singleflight"
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)
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func WithSingleFlight(component string, origin BlobStore) BlobStore {
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return &singleflightStore{
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BlobStore: origin,
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component: component,
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sf: new(singleflight.Group),
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}
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}
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type singleflightStore struct {
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BlobStore
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component string
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sf *singleflight.Group
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}
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func (s *singleflightStore) Name() string {
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return "sf_" + s.BlobStore.Name()
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}
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// Get 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) Get(hash string) (stream.Blob, error) {
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metrics.CacheWaitingRequestsCount.With(metrics.CacheLabels(s.BlobStore.Name(), s.component)).Inc()
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defer metrics.CacheWaitingRequestsCount.With(metrics.CacheLabels(s.BlobStore.Name(), s.component)).Dec()
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blob, err, _ := s.sf.Do(hash, s.getter(hash))
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if err != nil {
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return nil, err
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}
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return blob.(stream.Blob), nil
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}
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// getter returns a function that gets a blob from the origin
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// only one getter per hash will be executing at a time
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func (s *singleflightStore) getter(hash string) func() (interface{}, error) {
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return func() (interface{}, error) {
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metrics.CacheOriginRequestsCount.With(metrics.CacheLabels(s.BlobStore.Name(), s.component)).Inc()
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defer metrics.CacheOriginRequestsCount.With(metrics.CacheLabels(s.BlobStore.Name(), s.component)).Dec()
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start := time.Now()
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blob, err := s.BlobStore.Get(hash)
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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.BlobStore.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 blob, nil
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}
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}
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