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, 30 insertions, 7 deletions

diff --git a/app.go b/app.go
index 2626be49..22264eb8 100644
--- a/app.go
+++ b/app.go
@@ -124,12 +124,6 @@ func (a *theApp) checkAuthenticationIfNotExists(domain *domain.Domain, w http.Re
 }
 
 func (a *theApp) tryAuxiliaryHandlers(w http.ResponseWriter, r *http.Request, https bool, host string, domain *domain.Domain) bool {
-	// short circuit content serving to check for a status page
-	if r.RequestURI == a.appConfig.StatusPath {
-		a.healthCheck(w, r, https)
-		return true
-	}
-
 	// Add auto redirect
 	if !https && a.RedirectHTTP {
 		a.redirectToHTTPS(w, r, http.StatusTemporaryRedirect)
@@ -177,6 +171,27 @@ func (a *theApp) routingMiddleware(handler http.Handler) http.Handler {
 	})
 }
 
+// healthCheckMiddleware is serving the application status check
+func (a *theApp) healthCheckMiddleware(handler http.Handler) (http.Handler, error) {
+	healthCheck := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		a.healthCheck(w, r, request.IsHTTPS(r))
+	})
+
+	loggedHealthCheck, err := logging.BasicAccessLogger(healthCheck, a.LogFormat, nil)
+	if err != nil {
+		return nil, err
+	}
+
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.RequestURI == a.appConfig.StatusPath {
+			loggedHealthCheck.ServeHTTP(w, r)
+			return
+		}
+
+		handler.ServeHTTP(w, r)
+	}), nil
+}
+
 // customHeadersMiddleware will inject custom headers into the response
 func (a *theApp) customHeadersMiddleware(handler http.Handler) http.Handler {
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
@@ -310,7 +325,6 @@ func (a *theApp) buildHandlerPipeline() (http.Handler, error) {
 	handler = a.auxiliaryMiddleware(handler)
 	handler = a.authMiddleware(handler)
 	handler = a.acmeMiddleware(handler)
-	handler = a.customHeadersMiddleware(handler)
 	handler, err := logging.AccessLogger(handler, a.LogFormat)
 	if err != nil {
 		return nil, err
@@ -322,6 +336,15 @@ func (a *theApp) buildHandlerPipeline() (http.Handler, error) {
 
 	handler = a.routingMiddleware(handler)
 
+	// Health Check
+	handler, err = a.healthCheckMiddleware(handler)
+	if err != nil {
+		return nil, err
+	}
+
+	// Custom response headers
+	handler = a.customHeadersMiddleware(handler)
+
 	return handler, nil
 }