Add namespace in function name for metrics

This commit adds namespace in function names while logging metrics to
prometheus, irrespective of the function is invoked with namespace suffix
or not.

This is also required to add multiple namespace support to faas-idler

https://github.com/openfaas-incubator/faas-idler/issues/37 which is part
of https://github.com/openfaas/faas-netes/issues/511

Signed-off-by: Vivek Singh <vivekkmr45@yahoo.in>

gateway/metrics/exporter.go

@@ -6,10 +6,12 @@ package metrics
 
 import (
 	"encoding/json"
+	"fmt"
 	"io/ioutil"
 	"net"
 	"net/http"
 	"net/url"
+	"path"
 	"time"
 
 	"log"
@@ -56,8 +58,14 @@ func (e *Exporter) Collect(ch chan<- prometheus.Metric) {
 
 	e.metricOptions.ServiceReplicasGauge.Reset()
 	for _, service := range e.services {
+		var serviceName string
+		if len(service.Namespace) > 0 {
+			serviceName = fmt.Sprintf("%s.%s", service.Name, service.Namespace)
+		} else {
+			serviceName = service.Name
+		}
 		e.metricOptions.ServiceReplicasGauge.
-			WithLabelValues(service.Name).
+			WithLabelValues(serviceName).
 			Set(float64(service.Replicas))
 	}
 
@@ -72,9 +80,46 @@ func (e *Exporter) StartServiceWatcher(endpointURL url.URL, metricsOptions Metri
 	ticker := time.NewTicker(interval)
 	quit := make(chan struct{})
 
-	timeout := 3 * time.Second
+	go func() {
+		for {
+			select {
+			case <-ticker.C:
 
-	proxyClient := http.Client{
+				namespaces, err := e.getNamespaces(endpointURL)
+				if err != nil {
+					log.Println(err)
+				}
+
+				if len(namespaces) == 0 {
+					emptyNamespace := ""
+					services, err := e.getFunctions(endpointURL, emptyNamespace)
+					if err != nil {
+						log.Println(err)
+						continue
+					}
+					e.services = services
+				} else {
+					for _, namespace := range namespaces {
+						services, err := e.getFunctions(endpointURL, namespace)
+						if err != nil {
+							log.Println(err)
+							continue
+						}
+						e.services = append(e.services, services...)
+					}
+				}
+
+				break
+			case <-quit:
+				return
+			}
+		}
+	}()
+}
+
+func (e *Exporter) getHTTPClient(timeout time.Duration) http.Client {
+
+	return http.Client{
 		Transport: &http.Transport{
 			Proxy: http.ProxyFromEnvironment,
 			DialContext: (&net.Dialer{
@@ -87,45 +132,70 @@ func (e *Exporter) StartServiceWatcher(endpointURL url.URL, metricsOptions Metri
 			ExpectContinueTimeout: 1500 * time.Millisecond,
 		},
 	}
-
-	go func() {
-		for {
-			select {
-			case <-ticker.C:
-
-				get, err := http.NewRequest(http.MethodGet, endpointURL.String()+"system/functions", nil)
-				if err != nil {
-					log.Println(err)
-					return
-				}
-
-				if e.credentials != nil {
-					get.SetBasicAuth(e.credentials.User, e.credentials.Password)
-				}
-
-				services := []types.FunctionStatus{}
-				res, err := proxyClient.Do(get)
-				if err != nil {
-					log.Println(err)
-					continue
-				}
-				bytesOut, readErr := ioutil.ReadAll(res.Body)
-				if readErr != nil {
-					log.Println(err)
-					continue
-				}
-				unmarshalErr := json.Unmarshal(bytesOut, &services)
-				if unmarshalErr != nil {
-					log.Println(err)
-					continue
-				}
-
-				e.services = services
-
-				break
-			case <-quit:
-				return
-			}
-		}
-	}()
+}
+
+func (e *Exporter) getFunctions(endpointURL url.URL, namespace string) ([]types.FunctionStatus, error) {
+	timeout := 3 * time.Second
+	proxyClient := e.getHTTPClient(timeout)
+
+	endpointURL.Path = path.Join(endpointURL.Path, "/system/functions")
+	if len(namespace) > 0 {
+		q := endpointURL.Query()
+		q.Set("namespace", namespace)
+		endpointURL.RawQuery = q.Encode()
+	}
+
+	get, _ := http.NewRequest(http.MethodGet, endpointURL.String(), nil)
+	if e.credentials != nil {
+		get.SetBasicAuth(e.credentials.User, e.credentials.Password)
+	}
+
+	services := []types.FunctionStatus{}
+	res, err := proxyClient.Do(get)
+	if err != nil {
+		return services, err
+	}
+
+	bytesOut, readErr := ioutil.ReadAll(res.Body)
+	if readErr != nil {
+		return services, readErr
+	}
+
+	unmarshalErr := json.Unmarshal(bytesOut, &services)
+	if unmarshalErr != nil {
+		return services, unmarshalErr
+	}
+	return services, nil
+}
+
+func (e *Exporter) getNamespaces(endpointURL url.URL) ([]string, error) {
+	namespaces := []string{}
+
+	get, _ := http.NewRequest(http.MethodGet, endpointURL.String()+"system/namespaces", nil)
+	if e.credentials != nil {
+		get.SetBasicAuth(e.credentials.User, e.credentials.Password)
+	}
+
+	timeout := 3 * time.Second
+	proxyClient := e.getHTTPClient(timeout)
+
+	res, err := proxyClient.Do(get)
+	if err != nil {
+		return namespaces, err
+	}
+
+	if res.StatusCode == http.StatusNotFound {
+		return namespaces, nil
+	}
+
+	bytesOut, readErr := ioutil.ReadAll(res.Body)
+	if readErr != nil {
+		return namespaces, readErr
+	}
+
+	unmarshalErr := json.Unmarshal(bytesOut, &namespaces)
+	if unmarshalErr != nil {
+		return namespaces, unmarshalErr
+	}
+	return namespaces, nil
 }