swarm: initial instrumentation (#15969)

* swarm: initial instrumentation with go-metrics

* swarm: initialise metrics collection and add ResettingTimer to HTTP requests

* swarm: update metrics flags names. remove redundant Timer.

* swarm: rename method for periodically updating gauges

* swarm: finalise metrics after feedback

* swarm/network: always init kad metrics containers

* swarm/network: off-by-one index in metrics containers

* swarm, metrics: resolved conflicts

1 files changed, 9 insertions, 0 deletions

diff --git a/swarm/api/http/error.go b/swarm/api/http/error.go
index dbd97182f..831cf23fe 100644
--- a/swarm/api/http/error.go
+++ b/swarm/api/http/error.go
@@ -29,12 +29,19 @@ import (
 	"time"
 
 	"github.com/ethereum/go-ethereum/log"
+	"github.com/ethereum/go-ethereum/metrics"
 	"github.com/ethereum/go-ethereum/swarm/api"
 )
 
 //templateMap holds a mapping of an HTTP error code to a template
 var templateMap map[int]*template.Template
 
+//metrics variables
+var (
+	htmlCounter = metrics.NewRegisteredCounter("api.http.errorpage.html.count", nil)
+	jsonCounter = metrics.NewRegisteredCounter("api.http.errorpage.json.count", nil)
+)
+
 //parameters needed for formatting the correct HTML page
 type ErrorParams struct {
 	Msg       string
@@ -132,6 +139,7 @@ func respond(w http.ResponseWriter, r *http.Request, params *ErrorParams) {
 
 //return a HTML page
 func respondHtml(w http.ResponseWriter, params *ErrorParams) {
+	htmlCounter.Inc(1)
 	err := params.template.Execute(w, params)
 	if err != nil {
 		log.Error(err.Error())
@@ -140,6 +148,7 @@ func respondHtml(w http.ResponseWriter, params *ErrorParams) {
 
 //return JSON
 func respondJson(w http.ResponseWriter, params *ErrorParams) {
+	jsonCounter.Inc(1)
 	w.Header().Set("Content-Type", "application/json")
 	json.NewEncoder(w).Encode(params)
 }