rpc: remove 1 sprintf from hot-path (#19471)

remove 1 sprintf for metrics label creation from hot-path

Author: AskAlexSharov

rpc/handler.go

@@ -575,8 +575,10 @@ func (h *handler) handleCall(cp *callProc, msg *jsonrpcMessage, stream jsonstrea
 		rpcRequestGauge.Inc()
 		if answer != nil && answer.Error != nil {
 			failedReqeustGauge.Inc()
+			callb.timerFailure.ObserveDuration(start)
+		} else {
+			callb.timerSuccess.ObserveDuration(start)
 		}
-		newRPCServingTimerMS(msg.Method, answer == nil || answer.Error == nil).ObserveDuration(start)
 	}
 	return answer
 }

rpc/json.go

@@ -93,8 +93,8 @@ func (msg *jsonrpcMessage) isUnsubscribe() bool {
 }
 
 func (msg *jsonrpcMessage) namespace() string {
-	elem := strings.SplitN(msg.Method, serviceMethodSeparator, 2)
-	return elem[0]
+	ns, _, _ := strings.Cut(msg.Method, serviceMethodSeparator)
+	return ns
 }
 
 func (msg *jsonrpcMessage) String() string {

rpc/service.go

@@ -30,6 +30,7 @@ import (
 
 	"github.com/erigontech/erigon/common/dbg"
 	"github.com/erigontech/erigon/common/log/v3"
+	"github.com/erigontech/erigon/diagnostics/metrics"
 	"github.com/erigontech/erigon/rpc/jsonstream"
 )
 
@@ -64,6 +65,9 @@ type callback struct {
 	isSubscribe bool           // true if this is a subscription callback
 	streamable  bool           // support JSON streaming (more efficient for large responses)
 	logger      log.Logger
+
+	timerSuccess metrics.Summary // pre-cached success timer, avoids per-call GetOrCreateSummary
+	timerFailure metrics.Summary // pre-cached failure timer
 }
 
 func (r *serviceRegistry) registerName(name string, rcvr any) error {
@@ -90,25 +94,30 @@ func (r *serviceRegistry) registerName(name string, rcvr any) error {
 		}
 		r.services[name] = svc
 	}
-	for name, cb := range callbacks {
+	for shortName, cb := range callbacks {
+		// Pre-cache metrics timers using the full "namespace_method" name so the
+		// hot call path never needs to call GetOrCreateSummary or fmt.Sprintf.
+		fullMethod := name + serviceMethodSeparator + shortName
+		cb.timerSuccess = newRPCServingTimerMS(fullMethod, true)
+		cb.timerFailure = newRPCServingTimerMS(fullMethod, false)
 		if cb.isSubscribe {
-			svc.subscriptions[name] = cb
+			svc.subscriptions[shortName] = cb
 		} else {
-			svc.callbacks[name] = cb
+			svc.callbacks[shortName] = cb
 		}
 	}
 	return nil
 }
 
 // callback returns the callback corresponding to the given RPC method name.
 func (r *serviceRegistry) callback(method string) *callback {
-	elem := strings.SplitN(method, serviceMethodSeparator, 2)
-	if len(elem) != 2 {
+	svc, name, ok := strings.Cut(method, serviceMethodSeparator)
+	if !ok {
 		return nil
 	}
 	r.mu.Lock()
 	defer r.mu.Unlock()
-	return r.services[elem[0]].callbacks[elem[1]]
+	return r.services[svc].callbacks[name]
 }
 
 // subscription returns a subscription callback in the given service.