pass instance selector headers as query parameters

src/app/Shared/Services/NotificationChannel.service.tsx

@@ -74,11 +74,36 @@ export class NotificationChannel {
         map((u) => {
           try {
             const wsUrl = new URL(u);
+            // set the proper protocol for WebSocket connection upgrade
             wsUrl.protocol = wsUrl.protocol.replace('http', 'ws');
+
+            // set the instance namespace and name headers as query parameters instead.
+            // This is not used by normal Cryostat Web operation, where the instance is
+            // always the server that is hosting the web instance itself. In the console
+            // plugin case, the <namespace, name> instance selector is normally sent to
+            // the plugin backend by custom HTTP request headers so that the plugin backend
+            // can proxy to the correct Cryostat server instance. We cannot set custom
+            // request headers in the WebSocket connection request, so we set them as query
+            // parameters instead so that the plugin backend can fall back to finding those.
+            const headers = this.ctx.headers();
+            if (headers.has('CRYOSTAT-SVC-NS')) {
+              wsUrl.searchParams.append('ns', headers.get('CRYOSTAT-SVC-NS')!);
+            }
+            if (headers.has('CRYOSTAT-SVC-NAME')) {
+              wsUrl.searchParams.append('name', headers.get('CRYOSTAT-SVC-NAME')!);
+            }
             return wsUrl.toString();
           } catch (e) {
             // wasn't a URL - assume it was a relative path alone, which is OK
-            return u;
+            const headers = this.ctx.headers();
+            const searchParams = new URLSearchParams();
+            if (headers.has('CRYOSTAT-SVC-NS')) {
+              searchParams.append('ns', headers.get('CRYOSTAT-SVC-NS')!);
+            }
+            if (headers.has('CRYOSTAT-SVC-NAME')) {
+              searchParams.append('name', headers.get('CRYOSTAT-SVC-NAME')!);
+            }
+            return `${u}?${searchParams}`;
           }
         }),
       ),