Move code to pkg

pkg/middlewares/emptybackendhandler/empty_backend_handler.go

@@ -0,0 +1,33 @@
+package emptybackendhandler
+
+import (
+	"net/http"
+
+	"github.com/containous/traefik/pkg/healthcheck"
+)
+
+// EmptyBackend is a middleware that checks whether the current Backend
+// has at least one active Server in respect to the healthchecks and if this
+// is not the case, it will stop the middleware chain and respond with 503.
+type emptyBackend struct {
+	next healthcheck.BalancerHandler
+}
+
+// New creates a new EmptyBackend middleware.
+func New(lb healthcheck.BalancerHandler) http.Handler {
+	return &emptyBackend{next: lb}
+}
+
+// ServeHTTP responds with 503 when there is no active Server and otherwise
+// invokes the next handler in the middleware chain.
+func (e *emptyBackend) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
+	if len(e.next.Servers()) == 0 {
+		rw.WriteHeader(http.StatusServiceUnavailable)
+		_, err := rw.Write([]byte(http.StatusText(http.StatusServiceUnavailable)))
+		if err != nil {
+			http.Error(rw, err.Error(), http.StatusInternalServerError)
+		}
+	} else {
+		e.next.ServeHTTP(rw, req)
+	}
+}