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/handlers/alerthandler.go

@@ -14,23 +14,25 @@ import (
 	"github.com/openfaas/faas/gateway/requests"
 )
 
-// DefaultMinReplicas is the minimal amount of replicas for a service.
-const DefaultMinReplicas = 1
+const (
+	// DefaultMinReplicas is the minimal amount of replicas for a service.
+	DefaultMinReplicas = 1
 
-// DefaultMaxReplicas is the amount of replicas a service will auto-scale up to.
-const DefaultMaxReplicas = 20
+	// DefaultMaxReplicas is the amount of replicas a service will auto-scale up to.
+	DefaultMaxReplicas = 20
 
-// DefaultScalingFactor is the defining proportion for the scaling increments.
-const DefaultScalingFactor = 20
+	// DefaultScalingFactor is the defining proportion for the scaling increments.
+	DefaultScalingFactor = 20
 
-// MinScaleLabel label indicating min scale for a function
-const MinScaleLabel = "com.openfaas.scale.min"
+	// MinScaleLabel label indicating min scale for a function
+	MinScaleLabel = "com.openfaas.scale.min"
 
-// MaxScaleLabel label indicating max scale for a function
-const MaxScaleLabel = "com.openfaas.scale.max"
+	// MaxScaleLabel label indicating max scale for a function
+	MaxScaleLabel = "com.openfaas.scale.max"
 
-// ScalingFactorLabel label indicates the scaling factor for a function
-const ScalingFactorLabel = "com.openfaas.scale.factor"
+	// ScalingFactorLabel label indicates the scaling factor for a function
+	ScalingFactorLabel = "com.openfaas.scale.factor"
+)
 
 // MakeAlertHandler handles alerts from Prometheus Alertmanager
 func MakeAlertHandler(service ServiceQuery) http.HandlerFunc {
@@ -130,5 +132,6 @@ func CalculateReplicas(status string, currentReplicas uint64, maxReplicas uint64
 	} else { // Resolved event.
 		newReplicas = minReplicas
 	}
+
 	return newReplicas
 }

gateway/handlers/forwarding_proxy.go

@@ -23,7 +23,7 @@ import (
 // functionMatcher parses out the service name (group 1) and rest of path (group 2).
 var functionMatcher = regexp.MustCompile("^/?(?:async-)?function/([^/?]+)([^?]*)")
 
-// Indicies and meta-data for functionMatcher regex parts
+// Indices and meta-data for functionMatcher regex parts
 const (
 	hasPathCount = 3
 	routeIndex   = 0 // routeIndex corresponds to /function/ or /async-function/

gateway/handlers/function_cache.go

@@ -31,6 +31,7 @@ type FunctionCache struct {
 // Set replica count for functionName
 func (fc *FunctionCache) Set(functionName string, serviceQueryResponse ServiceQueryResponse) {
 	fc.Sync.Lock()
+	defer fc.Sync.Unlock()
 
 	if _, exists := fc.Cache[functionName]; !exists {
 		fc.Cache[functionName] = &FunctionMeta{}
@@ -40,23 +41,23 @@ func (fc *FunctionCache) Set(functionName string, serviceQueryResponse ServiceQu
 	entry.LastRefresh = time.Now()
 	entry.ServiceQueryResponse = serviceQueryResponse
 
-	fc.Sync.Unlock()
 }
 
 // Get replica count for functionName
 func (fc *FunctionCache) Get(functionName string) (ServiceQueryResponse, bool) {
+
+	fc.Sync.Lock()
+	defer fc.Sync.Unlock()
+
 	replicas := ServiceQueryResponse{
 		AvailableReplicas: 0,
 	}
 
 	hit := false
-	fc.Sync.Lock()
-
 	if val, exists := fc.Cache[functionName]; exists {
 		replicas = val.ServiceQueryResponse
 		hit = !val.Expired(fc.Expiry)
 	}
 
-	fc.Sync.Unlock()
 	return replicas, hit
 }

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)

gateway/metrics/exporter.go

@@ -60,11 +60,14 @@ func (e *Exporter) Collect(ch chan<- prometheus.Metric) {
 func (e *Exporter) StartServiceWatcher(endpointURL url.URL, metricsOptions MetricOptions, label string, interval time.Duration) {
 	ticker := time.NewTicker(interval)
 	quit := make(chan struct{})
+
+	timeout := 3 * time.Second
+
 	proxyClient := http.Client{
 		Transport: &http.Transport{
 			Proxy: http.ProxyFromEnvironment,
 			DialContext: (&net.Dialer{
-				Timeout:   3 * time.Second,
+				Timeout:   timeout,
 				KeepAlive: 0,
 			}).DialContext,
 			MaxIdleConns:          1,

gateway/plugin/external.go

@@ -24,11 +24,13 @@ import (
 
 // NewExternalServiceQuery proxies service queries to external plugin via HTTP
 func NewExternalServiceQuery(externalURL url.URL, credentials *auth.BasicAuthCredentials) handlers.ServiceQuery {
+	timeout := 3 * time.Second
+
 	proxyClient := http.Client{
 		Transport: &http.Transport{
 			Proxy: http.ProxyFromEnvironment,
 			DialContext: (&net.Dialer{
-				Timeout:   3 * time.Second,
+				Timeout:   timeout,
 				KeepAlive: 0,
 			}).DialContext,
 			MaxIdleConns:          1,

gateway/requests/requests.go

@@ -1,6 +1,8 @@
 // Copyright (c) Alex Ellis 2017. All rights reserved.
 // Licensed under the MIT license. See LICENSE file in the project root for full license information.
 
+// Package requests package provides a client SDK or library for
+// the OpenFaaS gateway REST API
 package requests
 
 // CreateFunctionRequest create a function in the swarm.

gateway/types/readconfig.go

@@ -51,7 +51,7 @@ func parseIntOrDurationValue(val string, fallback time.Duration) time.Duration {
 	return duration
 }
 
-// Read fetches config from environmental variables.
+// Read fetches gateway server configuration from environmental variables
 func (ReadConfig) Read(hasEnv HasEnv) GatewayConfig {
 	cfg := GatewayConfig{
 		PrometheusHost: "prometheus",
@@ -117,7 +117,7 @@ func (ReadConfig) Read(hasEnv HasEnv) GatewayConfig {
 	return cfg
 }
 
-// GatewayConfig for the process.
+// GatewayConfig provides config for the API Gateway server process
 type GatewayConfig struct {
 
 	// HTTP timeout for reading a request from clients.

gateway/version/version.go

@@ -1,17 +1,20 @@
 package version
 
 var (
-	//Version release version of the provider
+	// Version release version of the provider
 	Version string
-	//GitCommit SHA of the last git commit
+
+	// GitCommitSHA is the Git SHA of the latest tag/release
 	GitCommitSHA string
-	//GitCommit message of the last commit
+
+	// GitCommitMessage as read from the latest tag/release
 	GitCommitMessage string
-	//DevVersion string for the development version
+
+	// DevVersion string for the development version
 	DevVersion = "dev"
 )
 
-//BuildVersion returns current version of the provider
+// BuildVersion returns current version of the provider
 func BuildVersion() string {
 	if len(Version) == 0 {
 		return DevVersion