Dynamic Configuration Refactoring

middlewares/emptybackendhandler/empty_backend_handler.go

@@ -0,0 +1,33 @@
+package emptybackendhandler
+
+import (
+	"net/http"
+
+	"github.com/containous/traefik/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)
+	}
+}

middlewares/emptybackendhandler/empty_backend_handler_test.go

@@ -0,0 +1,81 @@
+package emptybackendhandler
+
+import (
+	"fmt"
+	"net/http"
+	"net/http/httptest"
+	"net/url"
+	"testing"
+
+	"github.com/containous/traefik/testhelpers"
+	"github.com/stretchr/testify/assert"
+	"github.com/vulcand/oxy/roundrobin"
+)
+
+func TestEmptyBackendHandler(t *testing.T) {
+	testCases := []struct {
+		amountServer       int
+		expectedStatusCode int
+	}{
+		{
+			amountServer:       0,
+			expectedStatusCode: http.StatusServiceUnavailable,
+		},
+		{
+			amountServer:       1,
+			expectedStatusCode: http.StatusOK,
+		},
+	}
+
+	for _, test := range testCases {
+		test := test
+		t.Run(fmt.Sprintf("amount servers %d", test.amountServer), func(t *testing.T) {
+			t.Parallel()
+
+			handler := New(&healthCheckLoadBalancer{amountServer: test.amountServer})
+
+			recorder := httptest.NewRecorder()
+			req := httptest.NewRequest(http.MethodGet, "http://localhost", nil)
+
+			handler.ServeHTTP(recorder, req)
+
+			assert.Equal(t, test.expectedStatusCode, recorder.Result().StatusCode)
+		})
+	}
+}
+
+type healthCheckLoadBalancer struct {
+	amountServer int
+}
+
+func (lb *healthCheckLoadBalancer) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	w.WriteHeader(http.StatusOK)
+}
+
+func (lb *healthCheckLoadBalancer) Servers() []*url.URL {
+	servers := make([]*url.URL, lb.amountServer)
+	for i := 0; i < lb.amountServer; i++ {
+		servers = append(servers, testhelpers.MustParseURL("http://localhost"))
+	}
+	return servers
+}
+
+func (lb *healthCheckLoadBalancer) RemoveServer(u *url.URL) error {
+	return nil
+}
+
+func (lb *healthCheckLoadBalancer) UpsertServer(u *url.URL, options ...roundrobin.ServerOption) error {
+	return nil
+}
+
+func (lb *healthCheckLoadBalancer) ServerWeight(u *url.URL) (int, bool) {
+	return 0, false
+}
+
+func (lb *healthCheckLoadBalancer) NextServer() (*url.URL, error) {
+	return nil, nil
+}
+
+func (lb *healthCheckLoadBalancer) Next() http.Handler {
+	return nil
+}