Introducing UI update lock. (#186)

* Introducing UI update lock.

* Using actual threading Lock.

* Fix import order.

* Using lock as a context manager (with).

* Add logging for the lock.

* Avoid calling UI update fn from the polling thread when it's already running.

* Minor: comments.

* Update octoprint_octorelay/__init__.py

* test_input_polling__locked.

* Asserting the released lock in test_update_ui.

octoprint_octorelay/__init__.py

@@ -40,6 +40,7 @@ def __init__(self):
         self.polling_timer = None
         self.tasks = [] # of Task
         self.model = { index: {} for index in RELAY_INDEXES }
+        self.ui_update_lock = None
 
     def get_settings_version(self):
         return SETTINGS_VERSION
@@ -263,6 +264,7 @@ def reducer(agg, task):
         )
 
     def update_ui(self):
+        self.ui_update_lock = True # issue 186
         self._logger.debug("Updating the UI")
         settings = self._settings.get([], merged=True) # expensive
         upcoming = self.get_upcoming_tasks(filter(
@@ -290,6 +292,7 @@ def update_ui(self):
                     "deadline": int(upcoming[index].deadline * 1000) # ms for JS
                 }
             }
+        self.ui_update_lock = None # issue 186, once model is updated, the lock can be released
         self._logger.debug(f"The UI feed: {self.model}")
         self._plugin_manager.send_plugin_message(self._identifier, self.model)
 
@@ -315,6 +318,8 @@ def get_update_information(self):
     # Polling thread
     def input_polling(self):
         # self._logger.debug("input_polling") # in case your log file is too small
+        if self.ui_update_lock:
+            return # issue 186, avoid the update during the another one
         for index in RELAY_INDEXES:
             active = self.model[index]["active"]
             model_state = self.model[index]["relay_state"] # bool since v3.1

tests/test_init.py

@@ -460,6 +460,15 @@ def test_input_polling(self):
         self.plugin_instance.update_ui.assert_called_with()
         self.plugin_instance._logger.debug.assert_called_with("relay: r3 has changed its pin state")
 
+    def test_input_polling__locked(self):
+        # Should return immediately when the UI update is locked
+        self.plugin_instance.ui_update_lock = True
+        self.plugin_instance.update_ui = Mock()
+        relayConstructorMock.reset_mock()
+        self.plugin_instance.input_polling()
+        self.plugin_instance.update_ui.assert_not_called()
+        relayConstructorMock.assert_not_called()
+
     def test_update_ui(self):
         # Should send message via plugin manager containing actual settings and the relay state
         cases = [
@@ -501,6 +510,7 @@ def test_update_ui(self):
             self.plugin_instance._plugin_manager.send_plugin_message.assert_called_with(
                 "MockedIdentifier", expected_model
             )
+            self.assertIsNone(self.plugin_instance.ui_update_lock)
 
     @patch("os.system")
     def test_toggle_relay(self, system_mock):