Enable basic auth for service query / scaling on provider

- this is a blocking issue for auth with Docker Swarm
fixes #879

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

gateway/metrics/exporter.go

@@ -14,6 +14,7 @@ import (
 
 	"log"
 
+	"github.com/openfaas/faas-provider/auth"
 	"github.com/openfaas/faas/gateway/requests"
 	"github.com/prometheus/client_golang/prometheus"
 )
@@ -22,13 +23,15 @@ import (
 type Exporter struct {
 	metricOptions MetricOptions
 	services      []requests.Function
+	credentials   *auth.BasicAuthCredentials
 }
 
 // NewExporter creates a new exporter for the OpenFaaS gateway metrics
-func NewExporter(options MetricOptions) *Exporter {
+func NewExporter(options MetricOptions, credentials *auth.BasicAuthCredentials) *Exporter {
 	return &Exporter{
 		metricOptions: options,
 		services:      []requests.Function{},
+		credentials:   credentials,
 	}
 }
 
@@ -77,6 +80,9 @@ func (e *Exporter) StartServiceWatcher(endpointURL url.URL, metricsOptions Metri
 			case <-ticker.C:
 
 				get, _ := http.NewRequest(http.MethodGet, endpointURL.String()+"system/functions", nil)
+				if e.credentials != nil {
+					get.SetBasicAuth(e.credentials.User, e.credentials.Password)
+				}
 
 				services := []requests.Function{}
 				res, err := proxyClient.Do(get)