Make sending client httpstartstopevents configurable

#159

Switching off these events reduces the CPU load on gorouter and
doppler VMS significantly.

These events are of type "timer".

Note that they should not be switched off when the app-autoscaler
is used.

config/config.go

@@ -277,6 +277,8 @@ type Config struct {
 	PerRequestMetricsReporting bool `yaml:"per_request_metrics_reporting,omitempty"`
 
 	SendHttpStartStopServerEvent bool `yaml:"send_http_start_stop_server_event,omitempty"`
+
+	SendHttpStartStopClientEvent bool `yaml:"send_http_start_stop_client_event,omitempty"`
 }
 
 var defaultConfig = Config{
@@ -334,6 +336,8 @@ var defaultConfig = Config{
 	PerRequestMetricsReporting: true,
 
 	SendHttpStartStopServerEvent: true,
+
+	SendHttpStartStopClientEvent: true,
 }
 
 func DefaultConfig() (*Config, error) {

config/config_test.go

@@ -639,6 +639,17 @@ backends:
 			Expect(config.SendHttpStartStopServerEvent).To(BeFalse())
 		})
 
+		It("defaults SendHttpStartStopClientEvent to true", func() {
+			Expect(config.SendHttpStartStopClientEvent).To(Equal(true))
+		})
+
+		It("sets SendHttpStartStopClientEvent", func() {
+			var b = []byte(`send_http_start_stop_client_event: false`)
+			err := config.Initialize(b)
+			Expect(err).ToNot(HaveOccurred())
+			Expect(config.SendHttpStartStopClientEvent).To(BeFalse())
+		})
+
 	})
 
 	Describe("Process", func() {

proxy/proxy.go

@@ -125,6 +125,7 @@ func NewProxy(
 			DisableCompression:  true,
 			TLSClientConfig:     routeServiceTLSConfig,
 		},
+		IsInstrumented: cfg.SendHttpStartStopClientEvent,
 	}
 
 	prt := round_tripper.NewProxyRoundTripper(

proxy/round_tripper/dropsonde_round_tripper.go

@@ -30,6 +30,7 @@ func (d *dropsondeRoundTripper) CancelRequest(r *http.Request) {
 type FactoryImpl struct {
 	BackendTemplate      *http.Transport
 	RouteServiceTemplate *http.Transport
+	IsInstrumented       bool
 }
 
 func (t *FactoryImpl) New(expectedServerName string, isRouteService bool) ProxyRoundTripper {
@@ -52,5 +53,10 @@ func (t *FactoryImpl) New(expectedServerName string, isRouteService bool) ProxyR
 		TLSClientConfig:     customTLSConfig,
 		TLSHandshakeTimeout: template.TLSHandshakeTimeout,
 	}
-	return NewDropsondeRoundTripper(newTransport)
+	if t.IsInstrumented {
+		return NewDropsondeRoundTripper(newTransport)
+	} else {
+		return newTransport
+	}
+
 }