if the client requests HTML, render an HTML 503 Service Unavailable page.

Author: bohde

options/locale/locale_en-US.ini

@@ -117,6 +117,7 @@ files = Files
 
 error = Error
 error404 = The page you are trying to reach either <strong>does not exist</strong> or <strong>you are not authorized</strong> to view it.
+error503 = The server was unable to complete your request. Please try again later.
 go_back = Go Back
 invalid_data = Invalid data: %v
 

routers/common/qos.go

@@ -10,13 +10,18 @@ import (
 	"strings"
 
 	user_model "code.gitea.io/gitea/models/user"
+	"code.gitea.io/gitea/modules/log"
 	"code.gitea.io/gitea/modules/setting"
+	"code.gitea.io/gitea/modules/templates"
 	"code.gitea.io/gitea/modules/web/middleware"
+	giteacontext "code.gitea.io/gitea/services/context"
 
 	"github.com/bohde/codel"
 	"github.com/go-chi/chi/v5"
 )
 
+const tplStatus503 templates.TplName = "status/503"
+
 type Priority int
 
 func (p Priority) String() string {
@@ -70,8 +75,7 @@ func QoS() func(next http.Handler) http.Handler {
 			// Check if the request can begin processing.
 			err := c.Acquire(ctx, int(priority))
 			if err != nil {
-				// If it failed, the service is over capacity and should error
-				http.Error(w, "Service Unavailable", http.StatusServiceUnavailable)
+				renderServiceUnavailable(w, req)
 				return
 			}
 
@@ -110,3 +114,31 @@ func requestPriority(ctx context.Context) Priority {
 
 	return DefaultPriority
 }
+
+// renderServiceUnavailable will render an HTTP 503 Service
+// Unavailable page, providing HTML if the client accepts it.
+func renderServiceUnavailable(w http.ResponseWriter, req *http.Request) {
+	acceptsHTML := false
+	for _, part := range req.Header["Accept"] {
+		if strings.Contains(part, "text/html") {
+			acceptsHTML = true
+			break
+		}
+	}
+
+	// If the client doesn't accept HTML, then render a plain text response
+	if !acceptsHTML {
+		http.Error(w, "503 Service Unavailable", http.StatusServiceUnavailable)
+		return
+	}
+
+	tmplCtx := giteacontext.TemplateContext{}
+	tmplCtx["Locale"] = middleware.Locale(w, req)
+	ctxData := middleware.GetContextData(req.Context())
+	err := templates.HTMLRenderer().HTML(w, http.StatusServiceUnavailable, tplStatus503, ctxData, tmplCtx)
+	if err != nil {
+		log.Error("Error occurs again when rendering service unavailable page: %v", err)
+		w.WriteHeader(http.StatusInternalServerError)
+		_, _ = w.Write([]byte("Internal server error, please collect error logs and report to Gitea issue tracker"))
+	}
+}

routers/common/qos_test.go

@@ -4,6 +4,7 @@
 package common
 
 import (
+	"net/http"
 	"testing"
 
 	user_model "code.gitea.io/gitea/models/user"
@@ -61,3 +62,30 @@ func TestRequestPriority(t *testing.T) {
 		})
 	}
 }
+
+func TestRenderServiceUnavailable(t *testing.T) {
+	t.Run("HTML", func(t *testing.T) {
+		ctx, resp := contexttest.MockContext(t, "")
+		ctx.Req.Header.Set("Accept", "text/html")
+
+		renderServiceUnavailable(resp, ctx.Req)
+		assert.Equal(t, http.StatusServiceUnavailable, resp.Code)
+		assert.Contains(t, resp.Header().Get("Content-Type"), "text/html")
+
+		body := resp.Body.String()
+		assert.Contains(t, body, `lang="en-US"`)
+		assert.Contains(t, body, "503 Service Unavailable")
+	})
+
+	t.Run("plain", func(t *testing.T) {
+		ctx, resp := contexttest.MockContext(t, "")
+		ctx.Req.Header.Set("Accept", "text/plain")
+
+		renderServiceUnavailable(resp, ctx.Req)
+		assert.Equal(t, http.StatusServiceUnavailable, resp.Code)
+		assert.Contains(t, resp.Header().Get("Content-Type"), "text/plain")
+
+		body := resp.Body.String()
+		assert.Contains(t, body, "503 Service Unavailable")
+	})
+}

templates/status/503.tmpl

@@ -0,0 +1,12 @@
+{{template "base/head" .}}
+<div role="main" aria-label="503 Service Unavailable" class="page-content">
+  <div class="ui container">
+	<div class="status-page-error">
+	  <div class="status-page-error-title">503 Service Unavailable</div>
+	  <div class="tw-text-center">
+		<div class="tw-my-4">{{ctx.Locale.Tr "error503"}}</div>
+	  </div>
+	</div>
+  </div>
+</div>
+{{template "base/footer" .}}