Remove deprecated cache metrics code

The metrics tracker in cached blob statter was replaced with prometheus
metrics and no longer needed.
Remove unused log wrapping.

Signed-off-by: Derek McGowan <derek@mcgstyle.net>

registry/storage/blobcachemetrics.go

@@ -1,66 +0,0 @@
-package storage
-
-import (
-	"context"
-	"expvar"
-	"sync/atomic"
-
-	dcontext "github.com/docker/distribution/context"
-	"github.com/docker/distribution/registry/storage/cache"
-)
-
-type blobStatCollector struct {
-	metrics cache.Metrics
-}
-
-func (bsc *blobStatCollector) Hit() {
-	atomic.AddUint64(&bsc.metrics.Requests, 1)
-	atomic.AddUint64(&bsc.metrics.Hits, 1)
-}
-
-func (bsc *blobStatCollector) Miss() {
-	atomic.AddUint64(&bsc.metrics.Requests, 1)
-	atomic.AddUint64(&bsc.metrics.Misses, 1)
-}
-
-func (bsc *blobStatCollector) Metrics() cache.Metrics {
-	return bsc.metrics
-}
-
-func (bsc *blobStatCollector) Logger(ctx context.Context) cache.Logger {
-	return dcontext.GetLogger(ctx)
-}
-
-// blobStatterCacheMetrics keeps track of cache metrics for blob descriptor
-// cache requests. Note this is kept globally and made available via expvar.
-// For more detailed metrics, its recommend to instrument a particular cache
-// implementation.
-var blobStatterCacheMetrics cache.MetricsTracker = &blobStatCollector{}
-
-func init() {
-	registry := expvar.Get("registry")
-	if registry == nil {
-		registry = expvar.NewMap("registry")
-	}
-
-	cache := registry.(*expvar.Map).Get("cache")
-	if cache == nil {
-		cache = &expvar.Map{}
-		cache.(*expvar.Map).Init()
-		registry.(*expvar.Map).Set("cache", cache)
-	}
-
-	storage := cache.(*expvar.Map).Get("storage")
-	if storage == nil {
-		storage = &expvar.Map{}
-		storage.(*expvar.Map).Init()
-		cache.(*expvar.Map).Set("storage", storage)
-	}
-
-	storage.(*expvar.Map).Set("blobdescriptor", expvar.Func(func() interface{} {
-		// no need for synchronous access: the increments are atomic and
-		// during reading, we don't care if the data is up to date. The
-		// numbers will always *eventually* be reported correctly.
-		return blobStatterCacheMetrics
-	}))
-}

registry/storage/cache/cachedblobdescriptorstore.go

@@ -9,35 +9,9 @@ import (
 	"github.com/opencontainers/go-digest"
 )
 
-// Metrics is used to hold metric counters
-// related to the number of times a cache was
-// hit or missed.
-type Metrics struct {
-	Requests uint64
-	Hits     uint64
-	Misses   uint64
-}
-
-// Logger can be provided on the MetricsTracker to log errors.
-//
-// Usually, this is just a proxy to dcontext.GetLogger.
-type Logger interface {
-	Errorf(format string, args ...interface{})
-}
-
-// MetricsTracker represents a metric tracker
-// which simply counts the number of hits and misses.
-type MetricsTracker interface {
-	Hit()
-	Miss()
-	Metrics() Metrics
-	Logger(context.Context) Logger
-}
-
 type cachedBlobStatter struct {
 	cache   distribution.BlobDescriptorService
 	backend distribution.BlobDescriptorService
-	tracker MetricsTracker
 }
 
 var (
@@ -54,16 +28,6 @@ func NewCachedBlobStatter(cache distribution.BlobDescriptorService, backend dist
 	}
 }
 
-// NewCachedBlobStatterWithMetrics creates a new statter which prefers a cache and
-// falls back to a backend. Hits and misses will send to the tracker.
-func NewCachedBlobStatterWithMetrics(cache distribution.BlobDescriptorService, backend distribution.BlobDescriptorService, tracker MetricsTracker) distribution.BlobStatter {
-	return &cachedBlobStatter{
-		cache:   cache,
-		backend: backend,
-		tracker: tracker,
-	}
-}
-
 func (cbds *cachedBlobStatter) Stat(ctx context.Context, dgst digest.Digest) (distribution.Descriptor, error) {
 	cacheCount.WithValues("Request").Inc(1)
 
@@ -71,9 +35,6 @@ func (cbds *cachedBlobStatter) Stat(ctx context.Context, dgst digest.Digest) (di
 	desc, cacheErr := cbds.cache.Stat(ctx, dgst)
 	if cacheErr == nil {
 		cacheCount.WithValues("Hit").Inc(1)
-		if cbds.tracker != nil {
-			cbds.tracker.Hit()
-		}
 		return desc, nil
 	}
 
@@ -86,19 +47,15 @@ func (cbds *cachedBlobStatter) Stat(ctx context.Context, dgst digest.Digest) (di
 	if cacheErr == distribution.ErrBlobUnknown {
 		// cache doesn't have info. update it with info got from backend
 		cacheCount.WithValues("Miss").Inc(1)
-		if cbds.tracker != nil {
-			cbds.tracker.Miss()
-		}
 		if err := cbds.cache.SetDescriptor(ctx, dgst, desc); err != nil {
 			dcontext.GetLoggerWithField(ctx, "blob", dgst).WithError(err).Error("error from cache setting desc")
 		}
 		// we don't need to return cache error upstream if any. continue returning value from backend
-		return desc, nil
-	}
-
+	} else {
 		// unknown error from cache. just log and error. do not store cache as it may be trigger many set calls
 		dcontext.GetLoggerWithField(ctx, "blob", dgst).WithError(cacheErr).Error("error from cache stat(ing) blob")
 		cacheCount.WithValues("Error").Inc(1)
+	}
 
 	return desc, nil
 }
@@ -122,15 +79,3 @@ func (cbds *cachedBlobStatter) SetDescriptor(ctx context.Context, dgst digest.Di
 	}
 	return nil
 }
-
-func logErrorf(ctx context.Context, tracker MetricsTracker, format string, args ...interface{}) {
-	if tracker == nil {
-		return
-	}
-
-	logger := tracker.Logger(ctx)
-	if logger == nil {
-		return
-	}
-	logger.Errorf(format, args...)
-}