Fixes prometheus gauges

Fix session close. Now PWD gets disconnected from network before
deleting it.

services/instance.go

@@ -11,22 +11,10 @@ import (
 
 	"github.com/docker/docker/api/types"
 	"github.com/docker/docker/client"
-	"github.com/prometheus/client_golang/prometheus"
 )
 
 var rw sync.Mutex
 
-var (
-	instancesGauge = prometheus.NewGauge(prometheus.GaugeOpts{
-		Name: "instances",
-		Help: "Instances",
-	})
-)
-
-func init() {
-	prometheus.MustRegister(instancesGauge)
-}
-
 type Instance struct {
 	session      *Session                `json:"-"`
 	Name         string                  `json:"name"`
@@ -102,7 +90,7 @@ func NewInstance(session *Session) (*Instance, error) {
 
 	wsServer.BroadcastTo(session.Id, "new instance", instance.Name, instance.IP, instance.Hostname)
 
-	instancesGauge.Inc()
+	setGauges()
 
 	return instance, nil
 }
@@ -156,7 +144,7 @@ func DeleteInstance(session *Session, instance *Instance) error {
 
 	wsServer.BroadcastTo(session.Id, "delete instance", instance.Name)
 
-	instancesGauge.Dec()
+	setGauges()
 
 	return err
 }