Cache handles stale values

pycrest/eve.py

@@ -30,7 +30,7 @@
 
 
 class APICache(object):
-    def put(self, key, value):
+    def put(self, key, value, ex):
         raise NotImplementedError
 
     def get(self, key):
@@ -50,9 +50,9 @@ def __init__(self, path):
     def _getpath(self, key):
         return os.path.join(self.path, str(hash(key)) + '.cache')
 
-    def put(self, key, value):
+    def put(self, key, value, ex):
         with open(self._getpath(key), 'wb') as f:
-            f.write(zlib.compress(pickle.dumps(value, -1)))
+            f.write(zlib.compress(pickle.dumps((value, ex + time.time()), -1)))
         self._cache[key] = value
 
     def get(self, key):
@@ -61,7 +61,14 @@ def get(self, key):
 
         try:
             with open(self._getpath(key), 'rb') as f:
-                return pickle.loads(zlib.decompress(f.read()))
+                ret = pickle.loads(zlib.decompress(f.read()))
+                if ret[1] > time.time():
+                    return ret[0]
+
+            # if we are here, we got stale cache, so we can invalidate it
+            self.invalidate(key)
+            return None
+
         except IOError as ex:
             if ex.errno == 2:  # file does not exist (yet)
                 return None
@@ -85,10 +92,20 @@ def __init__(self):
         self._dict = {}
 
     def get(self, key):
-        return self._dict.get(key, None)
+        ret = self._dict.get(key, None)
+        if ret is not None and ret[1] > time.time():
+            # cache hit
+            return ret[0]
+        elif ret is None:
+            # cache miss
+            return None
+        else:
+            # stale, delete from cache
+            self.invalidate(key)
+            return None
 
-    def put(self, key, value):
-        self._dict[key] = value
+    def put(self, key, value, ex):
+        self._dict[key] = value, ex + time.time()
 
     def invalidate(self, key):
         self._dict.pop(key, None)
@@ -141,12 +158,9 @@ def get(self, resource, params=None):
         # check cache
         key = (resource, frozenset(self._session.headers.items()), frozenset(prms.items()))
         cached = self.cache.get(key)
-        if cached and cached['expires'] > time.time():
+        if cached:
             logger.debug('Cache hit for resource %s (params=%s)', resource, prms)
-            return cached['payload']
-        elif cached:
-            logger.debug('Cache stale for resource %s (params=%s)', resource, prms)
-            self.cache.invalidate(key)
+            return cached
         else:
             logger.debug('Cache miss for resource %s (params=%s', resource, prms)
 
@@ -161,7 +175,7 @@ def get(self, resource, params=None):
         key = (resource, frozenset(self._session.headers.items()), frozenset(prms.items()))
         expires = self._get_expires(res)
         if expires > 0:
-            self.cache.put(key, {'expires': time.time() + expires, 'payload': ret})
+            self.cache.put(key, ret, expires)
 
         return ret
 

tests/test_api.py

@@ -240,7 +240,7 @@ def test_pagination(url, request):
             recf = open(path, 'r')
             rec = pickle.loads(zlib.decompress(recf.read()))
             recf.close()
-            rec['expires'] = 1
+            rec = rec[0], 1
 
             recf = open(path, 'w')
             recf.write(zlib.compress(pickle.dumps(rec)))
@@ -436,7 +436,7 @@ def token_mock(url, request):
             recf = open(path, 'r')
             rec = pickle.loads(zlib.decompress(recf.read()))
             recf.close()
-            rec['expires'] = 1
+            rec = rec[0], 1
 
             recf = open(path, 'w')
             recf.write(zlib.compress(pickle.dumps(rec)))
@@ -462,15 +462,15 @@ def test_apicache(self, mock_open, mock_unlink, mock_mkdir, mock_isdir):
         # Just because pragma: no cover is ugly
         cache = pycrest.eve.APICache()
         self.assertRaises(NotImplementedError, lambda: cache.get("foo"))
-        self.assertRaises(NotImplementedError, lambda: cache.put("foo", "bar"))
+        self.assertRaises(NotImplementedError, lambda: cache.put("foo", "bar", time.time()))
         self.assertRaises(NotImplementedError, lambda: cache.invalidate("foo"))
 
         # Test default DictCache
         crest = pycrest.EVE()
         self.assertEqual(type(crest.cache).__name__, "DictCache")
         crest.cache.invalidate('nxkey')
         self.assertEqual(crest.cache.get('nxkey'), None)
-        crest.cache.put('key', 'value')
+        crest.cache.put('key', 'value', time.time() + 1)
         self.assertEqual(crest.cache.get('key'), 'value')
 
 
@@ -490,7 +490,7 @@ def test_apicache(self, mock_open, mock_unlink, mock_mkdir, mock_isdir):
         self.assertEqual(crest.cache.get('nxkey'), None)
 
         # cache (key, value) pair and retrieve it
-        crest.cache.put('key', 'value')
+        crest.cache.put('key', 'value', time.time() + 1)
         self.assertEqual(crest.cache.get('key'), 'value')
 
         # retrieve from disk
@@ -633,4 +633,4 @@ def brokenInt(url, request):
             with mock.patch('time.time') as mock_time:
                 mock_time.return_value = 0
                 eve.shouldCache()
-                self.assertEqual(list(eve.cache._dict.items())[0][1]['expires'], 300)
+                self.assertEqual(list(eve.cache._dict.items())[0][1][1], 300)