add metrics for backend_retries_total

middlewares/retry_test.go

@@ -0,0 +1,91 @@
+package middlewares
+
+import (
+	"fmt"
+	"io/ioutil"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+)
+
+func TestRetry(t *testing.T) {
+	testCases := []struct {
+		failAtCalls    []int
+		attempts       int
+		responseStatus int
+		listener       *countingRetryListener
+		retriedCount   int
+	}{
+		{
+			failAtCalls:    []int{1, 2},
+			attempts:       3,
+			responseStatus: http.StatusOK,
+			listener:       &countingRetryListener{},
+			retriedCount:   2,
+		},
+		{
+			failAtCalls:    []int{1, 2},
+			attempts:       2,
+			responseStatus: http.StatusBadGateway,
+			listener:       &countingRetryListener{},
+			retriedCount:   1,
+		},
+	}
+
+	for _, tc := range testCases {
+		// bind tc locally
+		tc := tc
+		tcName := fmt.Sprintf("FailAtCalls(%v) RetryAttempts(%v)", tc.failAtCalls, tc.attempts)
+
+		t.Run(tcName, func(t *testing.T) {
+			t.Parallel()
+
+			var httpHandler http.Handler
+			httpHandler = &networkFailingHTTPHandler{failAtCalls: tc.failAtCalls}
+			httpHandler = NewRetry(tc.attempts, httpHandler, tc.listener)
+
+			recorder := httptest.NewRecorder()
+			req, err := http.NewRequest("GET", "http://localhost:3000/ok", ioutil.NopCloser(nil))
+			if err != nil {
+				t.Fatalf("could not create request: %+v", err)
+			}
+
+			httpHandler.ServeHTTP(recorder, req)
+
+			if tc.responseStatus != recorder.Code {
+				t.Errorf("wrong status code %d, want %d", recorder.Code, tc.responseStatus)
+			}
+			if tc.retriedCount != tc.listener.timesCalled {
+				t.Errorf("RetryListener called %d times, want %d times", tc.listener.timesCalled, tc.retriedCount)
+			}
+		})
+	}
+}
+
+// networkFailingHTTPHandler is an http.Handler implementation you can use to test retries.
+type networkFailingHTTPHandler struct {
+	failAtCalls []int
+	callNumber  int
+}
+
+func (handler *networkFailingHTTPHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	handler.callNumber++
+
+	for _, failAtCall := range handler.failAtCalls {
+		if handler.callNumber == failAtCall {
+			w.WriteHeader(http.StatusBadGateway)
+			return
+		}
+	}
+
+	w.WriteHeader(http.StatusOK)
+}
+
+// countingRetryListener is a RetryListener implementation to count the times the Retried fn is called.
+type countingRetryListener struct {
+	timesCalled int
+}
+
+func (l *countingRetryListener) Retried(attempt int) {
+	l.timesCalled++
+}