Extract magic variables for server

gateway/metrics/swarmwatcher.go

@@ -15,7 +15,7 @@ import (
 
 // AttachSwarmWatcher adds a go-route to monitor the amount of service replicas in the swarm
 // matching a 'function' label.
-func AttachSwarmWatcher(dockerClient *client.Client, metricsOptions MetricOptions) {
+func AttachSwarmWatcher(dockerClient *client.Client, metricsOptions MetricOptions, label string) {
 	ticker := time.NewTicker(1 * time.Second)
 	quit := make(chan struct{})
 
@@ -35,7 +35,7 @@ func AttachSwarmWatcher(dockerClient *client.Client, metricsOptions MetricOption
 				}
 
 				for _, service := range services {
-					if len(service.Spec.TaskTemplate.ContainerSpec.Labels["function"]) > 0 {
+					if len(service.Spec.TaskTemplate.ContainerSpec.Labels[label]) > 0 {
 						metricsOptions.ServiceReplicasCounter.
 							WithLabelValues(service.Spec.Name).
 							Set(float64(*service.Spec.Mode.Replicated.Replicas))

gateway/server.go

@@ -11,6 +11,8 @@ import (
 	"github.com/alexellis/faas/gateway/metrics"
 	"github.com/docker/docker/client"
 
+	"fmt"
+
 	"github.com/gorilla/mux"
 )
 
@@ -52,15 +54,22 @@ func main() {
 
 	metricsHandler := metrics.PrometheusHandler()
 	r.Handle("/metrics", metricsHandler)
-	metrics.AttachSwarmWatcher(dockerClient, metricsOptions)
+
+	// This could exist in a separate process - records the replicas of each swarm service.
+	functionLabel := "function"
+	metrics.AttachSwarmWatcher(dockerClient, metricsOptions, functionLabel)
 
 	r.Handle("/", http.RedirectHandler("/ui/", http.StatusMovedPermanently)).Methods("GET")
 
+	readTimeout := 8 * time.Second
+	writeTimeout := 8 * time.Second
+	tcpPort := 8080
+
 	s := &http.Server{
-		Addr:           ":8080",
-		ReadTimeout:    8 * time.Second,
-		WriteTimeout:   8 * time.Second,
-		MaxHeaderBytes: 1 << 20,
+		Addr:           fmt.Sprintf(":%d", tcpPort),
+		ReadTimeout:    readTimeout,
+		WriteTimeout:   writeTimeout,
+		MaxHeaderBytes: http.DefaultMaxHeaderBytes, // 1MB - can be overridden by setting Server.MaxHeaderBytes.
 		Handler:        r,
 	}