[#312] wc: Add metrics

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

pkg/local_object_storage/writecache/put.go

@@ -3,6 +3,7 @@ package writecache
 import (
 	"context"
 	"errors"
+	"time"
 
 	"git.frostfs.info/TrueCloudLab/frostfs-api-go/v2/pkg/tracing"
 	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/blobstor/common"
@@ -33,6 +34,13 @@ func (c *cache) Put(ctx context.Context, prm common.PutPrm) (common.PutRes, erro
 		))
 	defer span.End()
 
+	startedAt := time.Now()
+	added := false
+	storageType := storageTypeUndefined
+	defer func() {
+		c.metrics.Put(time.Since(startedAt), added, storageType)
+	}()
+
 	c.modeMtx.RLock()
 	defer c.modeMtx.RUnlock()
 	if c.readOnly() {
@@ -51,9 +59,20 @@ func (c *cache) Put(ctx context.Context, prm common.PutPrm) (common.PutRes, erro
 	}
 
 	if sz <= c.smallObjectSize {
-		return common.PutRes{}, c.putSmall(oi)
+		storageType = storageTypeDB
+		err := c.putSmall(oi)
+		if err == nil {
+			added = true
+		}
+		return common.PutRes{}, err
 	}
-	return common.PutRes{}, c.putBig(ctx, oi.addr, prm)
+
+	storageType = storageTypeFSTree
+	err := c.putBig(ctx, oi.addr, prm)
+	if err == nil {
+		added = true
+	}
+	return common.PutRes{}, err
 }
 
 // putSmall persists small objects to the write-cache database and