Fix #26805: don't restart when requesting CSS or JS

Author: LEDfan

src/main/java/eu/openanalytics/shinyproxy/AppRequestInfo.java

@@ -53,7 +53,7 @@ public static AppRequestInfo fromRequestOrException(HttpServletRequest request)
         if (result == null) {
             throw new BadRequestException("Error parsing URL.");
         }
-        // do not user request.getParam() hear as it will inspect the request body and proxying the request will fail
+        // do not use request.getParam() here as it will inspect the request body and proxying the request will fail
         List<String> param = ServletUriComponentsBuilder.fromRequest(request).build().getQueryParams().get(PROXY_HINT_PARAM);
         if (param != null && param.size() > 0) {
             result = new AppRequestInfo(result.appName, result.appInstance, result.subPath, param.get(0));
@@ -132,4 +132,13 @@ public String getSubPath() {
     public String getProxyIdHint() {
         return proxyIdHint;
     }
+
+    public Boolean isCssOrJsResource() {
+        if (subPath != null) {
+            String lowerSubPath = subPath.toLowerCase();
+            return lowerSubPath.endsWith(".js") || lowerSubPath.endsWith(".css");
+        }
+        return false;
+    }
+
 }

src/main/java/eu/openanalytics/shinyproxy/ShinyProxyTestStrategy.java

@@ -68,7 +68,6 @@ public boolean testProxy(Proxy proxy) {
 					// proxy got stopped while loading -> no need to try to connect it since the container will already be deleted
 					return true;
 				}
-				System.out.println(proxy.getStatus());
 				URL testURL = new URL(targetURI.toString());
 				HttpURLConnection connection = ((HttpURLConnection) testURL.openConnection());
 				connection.setConnectTimeout(timeoutMs);

src/main/java/eu/openanalytics/shinyproxy/controllers/AppController.java

@@ -32,6 +32,8 @@
 import eu.openanalytics.shinyproxy.runtimevalues.AppInstanceKey;
 import eu.openanalytics.shinyproxy.runtimevalues.PublicPathKey;
 import eu.openanalytics.shinyproxy.runtimevalues.WebSocketReconnectionModeKey;
+import io.undertow.server.HttpServerExchange;
+import io.undertow.servlet.handlers.ServletRequestContext;
 import org.springframework.stereotype.Controller;
 import org.springframework.ui.ModelMap;
 import org.springframework.web.bind.annotation.RequestMapping;
@@ -40,6 +42,8 @@
 import org.springframework.web.servlet.support.ServletUriComponentsBuilder;
 
 import javax.inject.Inject;
+import javax.servlet.AsyncContext;
+import javax.servlet.ServletResponse;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
 import java.io.IOException;
@@ -114,6 +118,21 @@ public void appDirect(HttpServletRequest request, HttpServletResponse response)
 			response.setStatus(410);
 			response.getWriter().write("{\"status\":\"error\", \"message\":\"app_stopped_or_non_existent\"}");
 			return;
+		} else if (proxy == null && (appRequestInfo.isCssOrJsResource() || request.getHeader("Upgrade") != null)) {
+			// No proxy found and the request is for a CSS or JS file or a websocket connection.
+			// We do not start a new proxy instance, because this is most probably a background request by an old, stopped app
+			// We reply to the request after 10 seconds. This way the app should detect that it has been stopped before the resource is loaded.
+			// (simply returning an error code could trigger the error handling logic of the app)
+			response.setStatus(200);
+			final AsyncContext acontext = request.startAsync();
+			acontext.start(() -> {
+				try {
+					Thread.sleep(10000);
+				} catch (InterruptedException ignored) {
+				}
+				acontext.complete();
+			});
+			return;
 		} else if (proxy != null && appRequestInfo.getProxyIdHint() != null && !proxy.getId().equals(appRequestInfo.getProxyIdHint())) {
 			// the proxy was restarted by the client before the client was aware that the app was stopped externally
 			// therefore the proxy_id_hints are different.