Skip trace for router healthz endpoint (#1400)

Jaeger preserves the trace data of router healthz endpoints
which is not so helpful for monitoring function metrics and
consumes storage to store such trace data.

This PR uses `GetStartOptions` to examine the request's path and
check if it's a request to healthz endpoint. If yes, skip and not
to trace it.

charts/fission-all/templates/router.yaml

@@ -61,6 +61,8 @@ spec:
             value: {{ .Values.router.useEncodedPath | default false | quote }}
           - name: DEBUG_ENV
             value: {{ .Values.debugEnv | quote }}
+          - name: DISPLAY_ACCESS_LOG
+            value: {{ .Values.router.displayAccessLog | default false | quote }}
 {{- if .Values.analytics }}
           - name: ANALYTICS_URL
             value: "https://g.fission.sh/metrics"

charts/fission-all/values.yaml

@@ -63,6 +63,12 @@ router:
   deployAsDaemonSet: false
   svcAddressMaxRetries: 5
   svcAddressUpdateTimeout: 30s
+  
+  ## Display endpoint access logs
+  ## To be aware of enabling logging endpoint access log, it increases
+  ## router resource utilization when under heavy workloads.
+  displayAccessLog: false
+  
   ## Add annotations for router
   # svcAnnotations:
   #   cloud.google.com/load-balancer-type: Internal

charts/fission-core/templates/router.yaml

@@ -61,6 +61,8 @@ spec:
             value: {{ .Values.router.useEncodedPath | default false | quote }}
           - name: DEBUG_ENV
             value: {{ .Values.debugEnv | quote }}
+          - name: DISPLAY_ACCESS_LOG
+            value: {{ .Values.router.displayAccessLog | default false | quote }}
 {{- if .Values.analytics }}
           - name: ANALYTICS_URL
             value: "https://g.fission.sh/metrics"

charts/fission-core/values.yaml

@@ -50,6 +50,12 @@ router:
   deployAsDaemonSet: false
   svcAddressMaxRetries: 5
   svcAddressUpdateTimeout: 30s
+  
+  ## Display endpoint access logs
+  ## To be aware of enabling logging endpoint access log, it increases
+  ## router resource utilization when under heavy workloads.
+  displayAccessLog: false
+  
   ## Add annotations for router
   # svcAnnotations:
   #   cloud.google.com/load-balancer-type: Internal

pkg/router/router.go

@@ -45,6 +45,7 @@ import (
 	"net/http"
 	"os"
 	"strconv"
+	"strings"
 	"time"
 
 	"github.com/gorilla/mux"
@@ -77,14 +78,27 @@ func router(ctx context.Context, logger *zap.Logger, httpTriggerSet *HTTPTrigger
 	return mr
 }
 
-func serve(ctx context.Context, logger *zap.Logger, port int, tracingSamplingRate float64, httpTriggerSet *HTTPTriggerSet, resolver *functionReferenceResolver) {
+func serve(ctx context.Context, logger *zap.Logger, port int, tracingSamplingRate float64,
+	httpTriggerSet *HTTPTriggerSet, resolver *functionReferenceResolver, displayAccessLog bool) {
 	mr := router(ctx, logger, httpTriggerSet, resolver)
 	url := fmt.Sprintf(":%v", port)
 
 	http.ListenAndServe(url, &ochttp.Handler{
 		Handler: mr,
-		StartOptions: trace.StartOptions{
+		GetStartOptions: func(r *http.Request) trace.StartOptions {
-			Sampler: trace.ProbabilitySampler(tracingSamplingRate),
+			// do not trace router healthz endpoint
+			if strings.Compare(r.URL.Path, "/router-healthz") == 0 {
+				return trace.StartOptions{
+					Sampler: trace.NeverSample(),
+				}
+			}
+			if displayAccessLog {
+				logger.Info("path", zap.String("path", r.URL.Path),
+					zap.String("method", r.Method), zap.Any("header", r.Header))
+			}
+			return trace.StartOptions{
+				Sampler: trace.ProbabilitySampler(tracingSamplingRate),
+			}
 		},
 	})
 }
@@ -202,6 +216,16 @@ func Start(logger *zap.Logger, port int, executorUrl string) {
 			zap.Float64("default", tracingSamplingRate))
 	}
 
+	displayAccessLogStr := os.Getenv("DISPLAY_ACCESS_LOG")
+	displayAccessLog, err := strconv.ParseBool(displayAccessLogStr)
+	if err != nil {
+		displayAccessLog = false
+		logger.Error("failed to parse 'DISPLAY_ACCESS_LOG' - set to the default value",
+			zap.Error(err),
+			zap.String("value", displayAccessLogStr),
+			zap.Bool("default", displayAccessLog))
+	}
+
 	triggers, _, fnStore := makeHTTPTriggerSet(logger.Named("triggerset"), fmap, frmap, trmap, fissionClient, kubeClient, executor, restClient, &tsRoundTripperParams{
 		timeout:           timeout,
 		timeoutExponent:   timeoutExponent,
@@ -218,5 +242,5 @@ func Start(logger *zap.Logger, port int, executorUrl string) {
 	logger.Info("starting router", zap.Int("port", port))
 	ctx, cancel := context.WithCancel(context.Background())
 	defer cancel()
-	serve(ctx, logger, port, tracingSamplingRate, triggers, resolver)
+	serve(ctx, logger, port, tracingSamplingRate, triggers, resolver, displayAccessLog)
 }

pkg/router/router_test.go

@@ -99,7 +99,7 @@ func TestRouter(t *testing.T) {
 	tracingSamplingRate := .5
 	ctx, cancel := context.WithCancel(context.Background())
 	defer cancel()
-	go serve(ctx, logger, port, tracingSamplingRate, triggers, frr)
+	go serve(ctx, logger, port, tracingSamplingRate, triggers, frr, false)
 	time.Sleep(100 * time.Millisecond)
 
 	// hit the router