Prevent entities running multiple updates simultaneously (#6511)

* Protect entity for multible updates on same time.

* Address all comments / make update more robust

* fix unittest

* fix lint

* address comments

tests/helpers/test_entity.py

@@ -1,8 +1,7 @@
 """Test the entity helper."""
 # pylint: disable=protected-access
 import asyncio
-from unittest.mock import MagicMock
-from unittest.mock import patch
+from unittest.mock import MagicMock, patch
 
 import pytest
 
@@ -132,3 +131,68 @@ class TestHelpersEntity(object):
             self.hass.block_till_done()
         state = self.hass.states.get(self.entity.entity_id)
         assert state.attributes.get(ATTR_DEVICE_CLASS) == 'test_class'
+
+
+@asyncio.coroutine
+def test_warn_slow_update(hass):
+    """Warn we log when entity update takes a long time."""
+    update_call = False
+
+    @asyncio.coroutine
+    def async_update():
+        """Mock async update."""
+        nonlocal update_call
+        update_call = True
+
+    mock_entity = entity.Entity()
+    mock_entity.hass = hass
+    mock_entity.entity_id = 'comp_test.test_entity'
+    mock_entity.async_update = async_update
+
+    with patch.object(hass.loop, 'call_later', MagicMock()) \
+            as mock_call:
+        yield from mock_entity.async_update_ha_state(True)
+        assert mock_call.called
+        assert len(mock_call.mock_calls) == 2
+
+        timeout, logger_method = mock_call.mock_calls[0][1][:2]
+
+        assert timeout == entity.SLOW_UPDATE_WARNING
+        assert logger_method == entity._LOGGER.warning
+
+        assert mock_call().cancel.called
+
+        assert update_call
+
+
+@asyncio.coroutine
+def test_warn_slow_update_with_exception(hass):
+    """Warn we log when entity update takes a long time and trow exception."""
+    update_call = False
+
+    @asyncio.coroutine
+    def async_update():
+        """Mock async update."""
+        nonlocal update_call
+        update_call = True
+        raise AssertionError("Fake update error")
+
+    mock_entity = entity.Entity()
+    mock_entity.hass = hass
+    mock_entity.entity_id = 'comp_test.test_entity'
+    mock_entity.async_update = async_update
+
+    with patch.object(hass.loop, 'call_later', MagicMock()) \
+            as mock_call:
+        yield from mock_entity.async_update_ha_state(True)
+        assert mock_call.called
+        assert len(mock_call.mock_calls) == 2
+
+        timeout, logger_method = mock_call.mock_calls[0][1][:2]
+
+        assert timeout == entity.SLOW_UPDATE_WARNING
+        assert logger_method == entity._LOGGER.warning
+
+        assert mock_call().cancel.called
+
+        assert update_call