Fix #170 - lookup backend for marathon plugin so we can specify traefik.backend via labels on the container

provider/marathon.go

@@ -80,6 +80,7 @@ func (provider *Marathon) Provide(configurationChan chan<- types.ConfigMessage)
 
 func (provider *Marathon) loadMarathonConfig() *types.Configuration {
 	var MarathonFuncMap = template.FuncMap{
+		"getBackend":        provider.getBackend,
 		"getPort":           provider.getPort,
 		"getWeight":         provider.getWeight,
 		"getDomain":         provider.getDomain,
@@ -302,3 +303,10 @@ func (provider *Marathon) getFrontendRule(application marathon.Application) stri
 	}
 	return "Host"
 }
+
+func (provider *Marathon) getBackend(application marathon.Application) string {
+	if label, err := provider.getLabel(application, "traefik.backend"); err == nil {
+		return label
+	}
+	return replace("/", "-", application.ID)
+}

provider/marathon_test.go

@@ -800,3 +800,29 @@ func TestMarathonGetFrontendRule(t *testing.T) {
 		}
 	}
 }
+
+func TestMarathonGetBackend(t *testing.T) {
+	provider := &Marathon{}
+
+	applications := []struct {
+		application marathon.Application
+		expected    string
+	}{
+		{
+			application: marathon.Application{
+				ID: "foo",
+				Labels: map[string]string{
+					"traefik.backend": "bar",
+				},
+			},
+			expected: "bar",
+		},
+	}
+
+	for _, a := range applications {
+		actual := provider.getBackend(a.application)
+		if actual != a.expected {
+			t.Fatalf("expected %q, got %q", a.expected, actual)
+		}
+	}
+}

templates/marathon.tmpl

@@ -1,13 +1,13 @@
 {{$apps := .Applications}}
 [backends]{{range .Tasks}}
-    [backends.backend{{.AppID | replace "/" "-"}}.servers.server-{{.ID | replace "." "-"}}]
+    [backends.backend{{with index $apps 0 }}{{getBackend .}}{{end}}.servers.server-{{.ID | replace "." "-"}}]
     url = "{{getProtocol . $apps}}://{{.Host}}:{{getPort . $apps}}"
     weight = {{getWeight . $apps}}
 {{end}}
 
 [frontends]{{range .Applications}}
   [frontends.frontend{{.ID | replace "/" "-"}}]
-  backend = "backend{{.ID | replace "/" "-"}}"
+  backend = "backend{{getBackend .}}"
   passHostHeader = {{getPassHostHeader .}}
     [frontends.frontend{{.ID | replace "/" "-"}}.routes.route-host{{.ID | replace "/" "-"}}]
     rule = "{{getFrontendRule .}}"