Closed tree cache could not be started again

Author: tonyseek

kazoo/recipe/cache.py

@@ -62,6 +62,8 @@ def start(self):
         """
         if self._state == self.STATE_LATENT:
             self._state = self.STATE_STARTED
+        elif self._state == self.STATE_CLOSED:
+            raise KazooException('already closed')
         else:
             raise KazooException('already started')
 
@@ -77,6 +79,9 @@ def close(self):
         A closed cache was detached from ZooKeeper's changes. And all nodes
         will be invalidated.
 
+        Once a tree cache was closed, it could not be started again. You should
+        only close a tree cache while you want to recycle it.
+
         .. note::
 
             This method is not thread safe.

kazoo/tests/test_cache.py

@@ -62,10 +62,17 @@ def test_start(self):
         eq_(self.cache._root._state, TreeNode.STATE_LIVE)
 
     @raises(KazooException)
-    def test_start_twice(self):
+    def test_start_started(self):
         self.make_cache()
         self.cache.start()
 
+    @raises(KazooException)
+    def test_start_closed(self):
+        self.make_cache()
+        self.cache.start()
+        self.cache.close()
+        self.cache.start()
+
     def test_close(self):
         self.make_cache()
         self.wait_cache(since=TreeEvent.INITIALIZED)