Extract health check in its own middleware

This way we short-circuit health check requests and avoid doing domain
lookup for them. We also do not report them in exported Prometheus
metrics and this way avoid trigger alerts during deploys.

Related to:

* https://gitlab.com/gitlab-org/gitlab-pages/issues/350
* https://gitlab.com/gitlab-com/gl-infra/production/issues/1681

1 files changed, 54 insertions, 0 deletions

diff --git a/app_test.go b/app_test.go
index d78d6737..3c485804 100644
--- a/app_test.go
+++ b/app_test.go
@@ -3,12 +3,15 @@ package main
 import (
 	"crypto/tls"
 	"fmt"
+	"io"
 	"net/http"
+	"net/http/httptest"
 	"testing"
 
 	"github.com/stretchr/testify/require"
 
 	"gitlab.com/gitlab-org/gitlab-pages/internal/request"
+	"gitlab.com/gitlab-org/gitlab-pages/internal/source"
 )
 
 func Test_setRequestScheme(t *testing.T) {
@@ -58,3 +61,54 @@ func newGetRequestWithScheme(t *testing.T, scheme string, withTLS bool) *http.Re
 
 	return req
 }
+
+func TestHealthCheckMiddleware(t *testing.T) {
+	tests := []struct {
+		name   string
+		path   string
+		status int
+		body   string
+	}{
+		{
+			name:   "Not a healthcheck request",
+			path:   "/foo/bar",
+			status: http.StatusOK,
+			body:   "Hello from inner handler",
+		},
+		{
+			name:   "Healthcheck request",
+			path:   "/-/healthcheck",
+			status: http.StatusServiceUnavailable,
+			body:   "not yet ready\n",
+		},
+	}
+
+	app := theApp{
+		appConfig: appConfig{
+			StatusPath: "/-/healthcheck",
+		},
+	}
+
+	domains, err := source.NewDomains(app.appConfig)
+	require.NoError(t, err)
+	app.domains = domains
+
+	handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusOK)
+		io.WriteString(w, "Hello from inner handler")
+	})
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			r := httptest.NewRequest("GET", tc.path, nil)
+			rr := httptest.NewRecorder()
+
+			middleware, err := app.healthCheckMiddleware(handler)
+			require.NoError(t, err)
+			middleware.ServeHTTP(rr, r)
+
+			require.Equal(t, tc.status, rr.Code)
+			require.Equal(t, tc.body, rr.Body.String())
+		})
+	}
+}