redis metrics

* redis metrics

it is working but metrics are not very useful since default buckets
start from 5ms and almost all of them are in that range.

* remove extra comment

(cherry picked from commit ba1a1d74e7eb047dd1056548ccf0695e8846782c)
Signed-off-by: Derek McGowan <derek@mcgstyle.net>

registry/storage/cache/metrics/prom.go

@@ -0,0 +1,68 @@
+package metrics
+
+import (
+	"context"
+	"github.com/docker/distribution"
+	"github.com/docker/distribution/registry/storage/cache"
+	"github.com/docker/go-metrics"
+	"github.com/opencontainers/go-digest"
+	prometheus "github.com/docker/distribution/metrics"
+	"time"
+)
+
+type prometheusCacheProvider struct {
+	cache.BlobDescriptorCacheProvider
+	latencyTimer metrics.LabeledTimer
+}
+
+func NewPrometheusCacheProvider(wrap cache.BlobDescriptorCacheProvider, name, help string) cache.BlobDescriptorCacheProvider {
+	return &prometheusCacheProvider{
+		wrap,
+		// TODO: May want to have fine grained buckets since redis calls are generally <1ms and the default minimum bucket is 5ms.
+		prometheus.StorageNamespace.NewLabeledTimer(name, help, "operation"),
+	}
+}
+
+func (p *prometheusCacheProvider) Stat(ctx context.Context, dgst digest.Digest) (distribution.Descriptor, error) {
+	start := time.Now()
+	d, e := p.BlobDescriptorCacheProvider.Stat(ctx, dgst)
+	p.latencyTimer.WithValues("Stat").UpdateSince(start)
+	return d, e
+}
+
+func (p *prometheusCacheProvider) SetDescriptor(ctx context.Context, dgst digest.Digest, desc distribution.Descriptor) error {
+	start := time.Now()
+	e := p.BlobDescriptorCacheProvider.SetDescriptor(ctx, dgst, desc)
+	p.latencyTimer.WithValues("SetDescriptor").UpdateSince(start)
+	return e
+}
+
+type prometheusRepoCacheProvider struct {
+	distribution.BlobDescriptorService
+	latencyTimer metrics.LabeledTimer
+}
+
+func (p *prometheusRepoCacheProvider) Stat(ctx context.Context, dgst digest.Digest) (distribution.Descriptor, error) {
+	start := time.Now()
+	d, e := p.BlobDescriptorService.Stat(ctx, dgst)
+	p.latencyTimer.WithValues("RepoStat").UpdateSince(start)
+	return d, e
+}
+
+func (p *prometheusRepoCacheProvider) SetDescriptor(ctx context.Context, dgst digest.Digest, desc distribution.Descriptor) error {
+	start := time.Now()
+	e := p.BlobDescriptorService.SetDescriptor(ctx, dgst, desc)
+	p.latencyTimer.WithValues("RepoSetDescriptor").UpdateSince(start)
+	return e
+}
+
+func (p *prometheusCacheProvider) RepositoryScoped(repo string) (distribution.BlobDescriptorService, error) {
+	s, err := p.BlobDescriptorCacheProvider.RepositoryScoped(repo)
+	if err != nil {
+		return nil, err
+	}
+	return &prometheusRepoCacheProvider{
+		s,
+		p.latencyTimer,
+	}, nil
+}

registry/storage/cache/redis/redis.go

@@ -3,6 +3,7 @@ package redis
 import (
 	"context"
 	"fmt"
+	"github.com/docker/distribution/registry/storage/cache/metrics"
 
 	"github.com/docker/distribution"
 	"github.com/docker/distribution/reference"
@@ -34,9 +35,13 @@ type redisBlobDescriptorService struct {
 // NewRedisBlobDescriptorCacheProvider returns a new redis-based
 // BlobDescriptorCacheProvider using the provided redis connection pool.
 func NewRedisBlobDescriptorCacheProvider(pool *redis.Pool) cache.BlobDescriptorCacheProvider {
-	return &redisBlobDescriptorService{
+	return metrics.NewPrometheusCacheProvider(
+		&redisBlobDescriptorService{
 			pool: pool,
-	}
+		},
+		"cache_redis",
+		"Number of seconds taken by redis",
+	)
 }
 
 // RepositoryScoped returns the scoped cache.