Add some timing histogram stats (#2482)

Previously our gRPC client code called the wrong function, enabling server-side instead of client-side histograms.

Also, add a timing stat for the generate / store combination in OCSP Updater.

cmd/ocsp-updater/main.go

@@ -488,19 +488,20 @@ func (updater *OCSPUpdater) generateOCSPResponses(ctx context.Context, statuses
 	wait := func() {
 		sem <- 1 // Block until there's capacity.
 	}
-	done := func() {
+	done := func(start time.Time) {
 		<-sem // Indicate there's more capacity.
+		stats.TimingDuration("GenerateAndStore", time.Since(start))
 	}
 
 	work := func(status core.CertificateStatus) {
-		defer done()
+		defer done(updater.clk.Now())
 		meta, err := updater.generateResponse(ctx, status)
 		if err != nil {
 			updater.log.AuditErr(fmt.Sprintf("Failed to generate OCSP response: %s", err))
 			stats.Inc("Errors.ResponseGeneration", 1)
 			return
 		}
-		updater.stats.Inc("GeneratedResponses", 1)
+		stats.Inc("GeneratedResponses", 1)
 		err = updater.storeResponse(meta)
 		if err != nil {
 			updater.log.AuditErr(fmt.Sprintf("Failed to store OCSP response: %s", err))

grpc/client.go

@@ -28,7 +28,7 @@ func ClientSetup(c *cmd.GRPCClientConfig, tls *tls.Config, stats metrics.Scope)
 		return nil, errNilTLS
 	}
 
-	grpc_prometheus.EnableHandlingTimeHistogram()
+	grpc_prometheus.EnableClientHandlingTimeHistogram()
 
 	ci := clientInterceptor{stats.NewScope("gRPCClient"), clock.Default(), c.Timeout.Duration}
 	creds := bcreds.NewClientCredentials(tls.RootCAs, tls.Certificates)