Update comments

- updates comments and adds where missing
- updates locks so that unlock is done via defer instead of
at the end of the statement
- extracts timeout variable in two places
- remove makeClient() unused method from metrics package

No-harm changes tested via go build.

Signed-off-by: Alex Ellis (VMware) <alexellis2@gmail.com>

gateway/metrics/add_metrics.go

@@ -13,16 +13,10 @@ import (
 	"github.com/openfaas/faas/gateway/requests"
 )
 
-func makeClient() http.Client {
-	// Fine-tune the client to fail fast.
-	return http.Client{}
-}
-
 // AddMetricsHandler wraps a http.HandlerFunc with Prometheus metrics
 func AddMetricsHandler(handler http.HandlerFunc, prometheusQuery PrometheusQueryFetcher) http.HandlerFunc {
 
 	return func(w http.ResponseWriter, r *http.Request) {
-		// log.Printf("Calling upstream for function info\n")
 
 		recorder := httptest.NewRecorder()
 		handler.ServeHTTP(recorder, r)
@@ -56,7 +50,6 @@ func AddMetricsHandler(handler http.HandlerFunc, prometheusQuery PrometheusQuery
 			return
 		}
 
-		// log.Printf("Querying Prometheus API\n")
 		expr := url.QueryEscape(`sum(gateway_function_invocation_total{function_name=~".*", code=~".*"}) by (function_name, code)`)
 		// expr := "sum(gateway_function_invocation_total%7Bfunction_name%3D~%22.*%22%2C+code%3D~%22.*%22%7D)+by+(function_name%2C+code)"
 		results, fetchErr := prometheusQuery.Fetch(expr)
@@ -76,7 +69,6 @@ func AddMetricsHandler(handler http.HandlerFunc, prometheusQuery PrometheusQuery
 			return
 		}
 
-		// log.Printf("Writing bytesOut: %s\n", bytesOut)
 		w.Header().Set("Content-Type", "application/json")
 		w.WriteHeader(http.StatusOK)
 		w.Write(bytesOut)