refactor: send http status 503 for temporary errors

Signed-off-by: Michael Adler <[email protected]>

docs/operations.md

@@ -312,7 +312,7 @@ the cookie would have already timed out.
 Based on the plugin's response, wfx can:
 
 - Modify the incoming request before it undergoes further processing by wfx in the usual manner.
-- Send a preemptive response back to the client, such as a "permission denied" message.
+- Send a preemptive response back to the client, such as a "permission denied" or "service unavailable" message.
 - Leave the request unchanged.
 
 ### Use Cases

example/plugin/main.go

@@ -63,8 +63,8 @@ func main() {
 					Payload: &plugin.PayloadT{
 						Type: plugin.Payloadgenerated_plugin_client_Response,
 						Value: &client.ResponseT{
-							Status:  client.ResponseStatusDeny,
-							Content: []byte("Plugin is overloaded. Please try again later.\n"),
+							Status:  client.ResponseStatusError,
+							Content: []byte("Plugin overloaded. Please try again later.\n"),
 						},
 					},
 				}

fbs/client/response.fbs

@@ -15,6 +15,8 @@ enum ResponseStatus: byte {
   Accept = 1,
   // The request was modifified and may proceed.
   Modified = 2,
+  // There was a temporary problem processing the request.
+  Unavailable = 3,
 }
 
 // Response contains the response details for a client.

middleware/plugin/middleware.go

@@ -80,6 +80,8 @@ func (mw *MW) Wrap(next http.Handler) http.Handler {
 					w.WriteHeader(http.StatusOK)
 				case client.ResponseStatusDeny:
 					w.WriteHeader(http.StatusForbidden)
+				case client.ResponseStatusUnavailable:
+					w.WriteHeader(http.StatusServiceUnavailable)
 				}
 				_, _ = w.Write(val.Content)
 				return

middleware/plugin/middleware_test.go

@@ -84,6 +84,7 @@ func TestNewMiddleware_ModifyRequest(t *testing.T) {
 		},
 	}
 	handler.ServeHTTP(recorder, httpReq)
+	assert.Equal(t, http.StatusOK, recorder.Code)
 }
 
 func TestNewMiddleware_SendResponse(t *testing.T) {
@@ -123,6 +124,46 @@ func TestNewMiddleware_SendResponse(t *testing.T) {
 		},
 	}
 	handler.ServeHTTP(recorder, httpReq)
+	assert.Equal(t, http.StatusOK, recorder.Code)
+}
+
+func TestNewMiddleware_Unavailable(t *testing.T) {
+	p := NewTestPlugin()
+	go func() {
+		for msg := range p.chMessage {
+			msg.response <- plugin.PluginResponseT{
+				Cookie: msg.request.Cookie,
+				Payload: &plugin.PayloadT{
+					Type: plugin.Payloadgenerated_plugin_client_Response,
+					Value: &client.ResponseT{
+						Status: client.ResponseStatusUnavailable,
+						Envelope: []*client.EnvelopeT{
+							{Name: "User-Agent", Values: []string{"gotest"}},
+						},
+						Content: []byte{},
+					},
+				},
+			}
+		}
+	}()
+
+	chQuit := make(chan error)
+	mw, err := NewMiddleware(p, chQuit)
+	require.Nil(t, err)
+	t.Cleanup(mw.Shutdown)
+
+	handler := mw.Wrap(http.HandlerFunc(func(rw http.ResponseWriter, req *http.Request) {}))
+
+	recorder := httptest.NewRecorder()
+	httpReq := &http.Request{
+		Method: http.MethodGet,
+		URL: &url.URL{
+			Host: "localhost",
+			Path: "/foo",
+		},
+	}
+	handler.ServeHTTP(recorder, httpReq)
+	assert.Equal(t, http.StatusServiceUnavailable, recorder.Code)
 }
 
 func TestHttpMethodToAction(t *testing.T) {