[#312] wc: Add metrics

Signed-off-by: Dmitrii Stepanov <d.stepanov@yadro.com>

pkg/local_object_storage/writecache/get.go

@@ -2,6 +2,7 @@ package writecache
 
 import (
 	"context"
+	"time"
 
 	"git.frostfs.info/TrueCloudLab/frostfs-api-go/v2/pkg/tracing"
 	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/blobstor/common"
@@ -27,9 +28,22 @@ func (c *cache) Get(ctx context.Context, addr oid.Address) (*objectSDK.Object, e
 		))
 	defer span.End()
 
+	return c.getInternal(ctx, saddr, addr)
+}
+
+func (c *cache) getInternal(ctx context.Context, saddr string, addr oid.Address) (*objectSDK.Object, error) {
+	found := false
+	storageType := storageTypeUndefined
+	startedAt := time.Now()
+	defer func() {
+		c.metrics.Get(time.Since(startedAt), found, storageType)
+	}()
+
 	value, err := Get(c.db, []byte(saddr))
 	if err == nil {
 		obj := objectSDK.New()
+		found = true
+		storageType = storageTypeDB
 		return obj, obj.Unmarshal(value)
 	}
 
@@ -38,6 +52,8 @@ func (c *cache) Get(ctx context.Context, addr oid.Address) (*objectSDK.Object, e
 		return nil, logicerr.Wrap(apistatus.ObjectNotFound{})
 	}
 
+	found = true
+	storageType = storageTypeFSTree
 	return res.Object, nil
 }
 
@@ -45,13 +61,15 @@ func (c *cache) Get(ctx context.Context, addr oid.Address) (*objectSDK.Object, e
 //
 // Returns an error of type apistatus.ObjectNotFound if the requested object is missing in write-cache.
 func (c *cache) Head(ctx context.Context, addr oid.Address) (*objectSDK.Object, error) {
+	saddr := addr.EncodeToString()
+
 	ctx, span := tracing.StartSpanFromContext(ctx, "writecache.Head",
 		trace.WithAttributes(
-			attribute.String("address", addr.EncodeToString()),
+			attribute.String("address", saddr),
 		))
 	defer span.End()
 
-	obj, err := c.Get(ctx, addr)
+	obj, err := c.getInternal(ctx, saddr, addr)
 	if err != nil {
 		return nil, err
 	}