metrics: Initial integration of Prometheus metrics (#3709)

Signed-off-by: Dave Henderson <dhenderson@gmail.com>

1 files changed, 66 insertions, 0 deletions

diff --git a/modules/caddyhttp/metrics_test.go b/modules/caddyhttp/metrics_test.go
new file mode 100644
index 0000000..5c3bc1d
--- /dev/null
+++ b/modules/caddyhttp/metrics_test.go
@@ -0,0 +1,66 @@
+package caddyhttp
+
+import (
+	"context"
+	"errors"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/prometheus/client_golang/prometheus/testutil"
+)
+
+func TestServerNameFromContext(t *testing.T) {
+	ctx := context.Background()
+	expected := "UNKNOWN"
+	if actual := serverNameFromContext(ctx); actual != expected {
+		t.Errorf("Not equal: expected %q, but got %q", expected, actual)
+	}
+
+	in := "foo"
+	ctx = contextWithServerName(ctx, in)
+	if actual := serverNameFromContext(ctx); actual != in {
+		t.Errorf("Not equal: expected %q, but got %q", in, actual)
+	}
+}
+
+func TestMetricsInstrumentedHandler(t *testing.T) {
+	handlerErr := errors.New("oh noes")
+	response := []byte("hello world!")
+	h := HandlerFunc(func(w http.ResponseWriter, r *http.Request) error {
+		if actual := testutil.ToFloat64(httpMetrics.requestInFlight); actual != 1.0 {
+			t.Errorf("Not same: expected %#v, but got %#v", 1.0, actual)
+		}
+		if handlerErr == nil {
+			w.Write(response)
+		}
+		return handlerErr
+	})
+
+	mh := middlewareHandlerFunc(func(w http.ResponseWriter, r *http.Request, h Handler) error {
+		return h.ServeHTTP(w, r)
+	})
+
+	ih := newMetricsInstrumentedHandler("foo", "bar", mh)
+
+	r := httptest.NewRequest("GET", "/", nil)
+	w := httptest.NewRecorder()
+
+	if actual := ih.ServeHTTP(w, r, h); actual != handlerErr {
+		t.Errorf("Not same: expected %#v, but got %#v", handlerErr, actual)
+	}
+	if actual := testutil.ToFloat64(httpMetrics.requestInFlight); actual != 0.0 {
+		t.Errorf("Not same: expected %#v, but got %#v", 0.0, actual)
+	}
+
+	handlerErr = nil
+	if err := ih.ServeHTTP(w, r, h); err != nil {
+		t.Errorf("Received unexpected error: %w", err)
+	}
+}
+
+type middlewareHandlerFunc func(http.ResponseWriter, *http.Request, Handler) error
+
+func (f middlewareHandlerFunc) ServeHTTP(w http.ResponseWriter, r *http.Request, h Handler) error {
+	return f(w, r, h)
+}