In CachedUpdatePersister don't load model if we already have active

CHANGES.txt

@@ -1,6 +1,8 @@
 v1.2 - unreleased
 =================
 
+- In CachedUpdatePersister don't load model if we already have active
+
 - Allow for use of multiple CachedUpdatePersisters
 
   Instances of CachedUpdatePersister now use their own name inside the

palladium/persistence.py

@@ -569,10 +569,12 @@ class CachedUpdatePersister(ModelPersister):
 
     cache = process_store
     __pld_config_key__ = 'cachedupdatepersister_default'
+    _loaded_version = None
 
     def __init__(self,
                  impl,
-                 update_cache_rrule=None
+                 update_cache_rrule=None,
+                 check_version=True,
                  ):
         """
         :param ModelPersister impl:
@@ -583,9 +585,15 @@ def __init__(self,
           :class:`dateutil.rrule.rrule` that determines when the cache
           will be updated.  See :class:`~palladium.util.RruleThread` for
           details.
+
+        :param bool check_version:
+          If set to `True`, I will perform a check and only load a new
+          model from the storage if my cached version differs from
+          what's the current active version.
         """
         self.impl = impl
         self.update_cache_rrule = update_cache_rrule
+        self.check_version = check_version
 
     def initialize_component(self, config):
         self.use_cache = config.get('__mode__') != 'fit'
@@ -611,9 +619,20 @@ def read(self, *args, **kwargs):
 
     @PluggableDecorator('update_model_decorators')
     def update_cache(self, *args, **kwargs):
+        active_version = None
+
+        if self.check_version:
+            active_version = self.list_properties()['active-model']
+            if self._loaded_version == (active_version, args, kwargs):
+                return
+
         model = self.impl.read(*args, **kwargs)
         if model is not None:
             self.cache[self.__pld_config_key__] = model
+
+            if self.check_version:
+                self._loaded_version = (active_version, args, kwargs)
+
             return model
 
     @PluggableDecorator('write_model_decorators')

palladium/tests/test_persistence.py

@@ -769,9 +769,23 @@ def test_write(self, persister):
         persister.impl.write.assert_called_with('mymodel')
 
     def test_update_cache(self, persister):
+        persister.update_cache()
+        assert persister.read() is persister.impl.read.return_value
+        persister.impl.read.assert_called_with()
+        assert len(persister.impl.read.mock_calls) == 1
+
+    def test_update_cache_no_check_version(self, persister):
+        persister.check_version = False
+        persister.update_cache()
+        assert persister.read() is persister.impl.read.return_value
+        persister.impl.read.assert_called_with()
+        assert len(persister.impl.read.mock_calls) == 2
+
+    def test_update_cache_specific_version(self, persister):
         persister.update_cache(version=123)
         assert persister.read() is persister.impl.read.return_value
         persister.impl.read.assert_called_with(version=123)
+        assert len(persister.impl.read.mock_calls) == 2
 
     def test_update_cache_rrule(self, process_store, CachedUpdatePersister,
                                 config):