closes #980

CHANGES.md

@@ -1,6 +1,11 @@
+## Version 3.0.0 (in development)
+
+* Added a Web API function `keep_alive` that is periodically used by Cate App  
+  to avoid loosing an open WebSocket connection. (#980)
+
 ## Version 2.1.5
 
-* Fixed problem that prevented storing user preferences from Cate App if the
+* Fixed a problem that prevented storing user preferences from Cate App if the
   preferences file did not yet exist.
 * The parameters of operation `temporal_aggregation` have been changed. Both parameters
   `output_resolution` and `custom_resolution` have been replaced by a single parameter 

cate/webapi/websocket.py

@@ -74,6 +74,10 @@ def _serialize_workspace(self, workspace: Workspace) -> dict:
                                                                        self.workspace_manager.root_path)
         return workspace_json
 
+    def keep_alive(self):
+        """This operation is used to keep the WebSocket connection alive."""
+        pass
+
     def get_config(self) -> dict:
         return dict(data_stores_path=conf.get_data_stores_path(),
                     use_workspace_imagery_cache=conf.get_use_workspace_imagery_cache(),

tests/webapi/test_websocket.py

@@ -28,6 +28,10 @@ def tearDown(self):
         if os.path.exists(self._workspace_dir):
             shutil.rmtree(self._workspace_dir)
 
+    @unittest.skipIf(os.environ.get('CATE_DISABLE_WEB_TESTS', None) == '1', 'CATE_DISABLE_WEB_TESTS = 1')
+    def test_keep_alive(self):
+        self.assertIsNone(self.service.keep_alive())
+
     @unittest.skipIf(os.environ.get('CATE_DISABLE_WEB_TESTS', None) == '1', 'CATE_DISABLE_WEB_TESTS = 1')
     def test_get_data_stores(self):
         data_stores = self.service.get_data_stores()