notifications: fix expvar for Go 1.7

Remove EndpointConfig.Transport from the return value of the
registry.notifications.endpoints expvar.Func.  It results in an empty
value for that expvar variable under Go 1.7 because it is a non-nil
*http.Transport, which Go 1.7 can no longer encode as JSON.

Signed-off-by: Noah Treuhaft <noah.treuhaft@docker.com>

notifications/endpoint.go

@@ -13,7 +13,7 @@ type EndpointConfig struct {
 	Threshold         int
 	Backoff           time.Duration
 	IgnoredMediaTypes []string
-	Transport         *http.Transport
+	Transport         *http.Transport `json:"-"`
 }
 
 // defaults set any zero-valued fields to a reasonable default.

notifications/metrics_test.go

@@ -0,0 +1,28 @@
+package notifications
+
+import (
+	"encoding/json"
+	"expvar"
+	"testing"
+)
+
+func TestMetricsExpvar(t *testing.T) {
+	endpointsVar := expvar.Get("registry").(*expvar.Map).Get("notifications").(*expvar.Map).Get("endpoints")
+
+	var v interface{}
+	if err := json.Unmarshal([]byte(endpointsVar.String()), &v); err != nil {
+		t.Fatalf("unexpected error unmarshaling endpoints: %v", err)
+	}
+	if v != nil {
+		t.Fatalf("expected nil, got %#v", v)
+	}
+
+	NewEndpoint("x", "y", EndpointConfig{})
+
+	if err := json.Unmarshal([]byte(endpointsVar.String()), &v); err != nil {
+		t.Fatalf("unexpected error unmarshaling endpoints: %v", err)
+	}
+	if slice, ok := v.([]interface{}); !ok || len(slice) != 1 {
+		t.Logf("expected one-element []interface{}, got %#v", v)
+	}
+}