update logic for checking missing / expired cache key

Author: anthonyp97

cache_helper/decorators.py

@@ -13,6 +13,8 @@
 from cache_helper import utils
 
 logger = logging.getLogger(__name__)
+CACHE_KEY_NOT_FOUND = 'cache_key_not_found'
+
 
 def cached(timeout):
     def _cached(func):
@@ -24,22 +26,21 @@ def wrapper(*args, **kwargs):
             cache_key = utils.get_hashed_cache_key(function_cache_key)
 
             try:
-                value = cache.get(cache_key)
+                value = cache.get(cache_key, CACHE_KEY_NOT_FOUND)
             except Exception:
                 logger.warning(
                     f'Error retrieving value from Cache for Key: {function_cache_key}',
                     exc_info=True,
                 )
-                value = None
+                value = CACHE_KEY_NOT_FOUND
 
-            if value is None:
+            if value == CACHE_KEY_NOT_FOUND:
                 value = func(*args, **kwargs)
                 # Try and set the key, value pair in the cache.
                 # But if it fails on an error from the underlying
                 # cache system, handle it.
                 try:
                     cache.set(cache_key, value, timeout)
-
                 except CacheSetError:
                     logger.warning(
                         f'Error saving value to Cache for Key: {function_cache_key}',
@@ -79,15 +80,15 @@ def wrapper(*args, **kwargs):
             cache_key = utils.get_hashed_cache_key(function_cache_key)
 
             try:
-                value = cache.get(cache_key)
+                value = cache.get(cache_key, CACHE_KEY_NOT_FOUND)
             except Exception:
                 logger.warning(
                     f'Error retrieving value from Cache for Key: {function_cache_key}',
                     exc_info=True,
                 )
-                value = None
+                value = CACHE_KEY_NOT_FOUND
 
-            if value is None:
+            if value == CACHE_KEY_NOT_FOUND:
                 value = func(*args, **kwargs)
                 # Try and set the key, value pair in the cache.
                 # But if it fails on an error from the underlying
@@ -151,14 +152,15 @@ def __get__(self, obj, objtype):
         def __call__(self, *args, **kwargs):
             cache_key, function_cache_key = self.create_cache_key(*args, **kwargs)
             try:
-                value = cache.get(cache_key)
+                value = cache.get(cache_key, CACHE_KEY_NOT_FOUND)
             except Exception:
                 logger.warning(
                     f'Error retrieving value from Cache for Key: {function_cache_key}',
                     exc_info=True,
                 )
-                value = None
-            if value is None:
+                value = CACHE_KEY_NOT_FOUND
+
+            if value == CACHE_KEY_NOT_FOUND:
                 value = self.func(*args, **kwargs)
                 # Try and set the key, value pair in the cache.
                 # But if it fails on an error from the underlying
@@ -170,6 +172,7 @@ def __call__(self, *args, **kwargs):
                         f'Error saving value to Cache for Key: {function_cache_key}',
                         exc_info=True,
                     )
+
             return value
 
         def _invalidate(self, *args, **kwargs):