Dont rewrite content identical to cached data

Author: shin-

depends/docker-registry-core/docker_registry/core/lru.py

@@ -66,6 +66,11 @@ def wrapper(*args):
         key = args[-2]
         key = cache_key(key)
         try:
+            cached_content = get_by_key(key)
+            if cached_content and cached_content == content:
+                # If cached content is the same as what we are about to
+                # write, we don't need to write again.
+                return args[-2]
             redis_conn.set(key, content)
         except redis.exceptions.ConnectionError as e:
             logging.warning("LRU: Redis connection error: {0}".format(e))
@@ -81,11 +86,7 @@ def get(f):
     def wrapper(*args):
         key = args[-1]
         key = cache_key(key)
-        try:
-            content = redis_conn.get(key)
-        except redis.exceptions.ConnectionError as e:
-            logging.warning("LRU: Redis connection error: {0}".format(e))
-            content = None
+        content = get_by_key(key)
 
         if content is not None:
             return content
@@ -102,6 +103,15 @@ def wrapper(*args):
     return wrapper
 
 
+def get_by_key(key):
+    try:
+        content = redis_conn.get(key)
+    except redis.exceptions.ConnectionError as e:
+        logging.warning("LRU: Redis connection error: {0}".format(e))
+        return None
+    return content
+
+
 def remove(f):
     @functools.wraps(f)
     def wrapper(*args):