decorators.Cache Attach an unique id to objects

tools/telemetry/telemetry/decorators.py

Index: tools/telemetry/telemetry/decorators.py
diff --git a/tools/telemetry/telemetry/decorators.py b/tools/telemetry/telemetry/decorators.py
index 228c987ddf539bdb58096561e4acf588fcff91dd..12cdc1646af8e2e86f05f0279d693a0607f2c850 100644
--- a/tools/telemetry/telemetry/decorators.py
+++ b/tools/telemetry/telemetry/decorators.py
@@ -4,6 +4,7 @@
 
 import functools
 import types
+import uuid
 
 
 def Cache(obj):
@@ -22,6 +23,18 @@ def Cache(obj):
   @functools.wraps(obj)
   def Cacher(*args, **kwargs):
     key = str(args) + str(kwargs)
+
+    if len(args) > 0:
+      self = args[0]
+      if not hasattr(self, '__CacheUniqueId'):
+        try:
+          self.__CacheUniqueId = uuid.uuid4().hex

[tonyg, 2014/07/25 21:13:55]

Thanks for digging into this!!

Looking again at this code, I wonder whether the root problem is that the
__cache lives on the function object instead of the instance. In addition to
causing the problem you noticed, it also seems prone to leaking memory.

I wonder whether this (or something similar) works instead:

if args and isinstance(args[0], obj):
  cache = args[0].__cache = {}

This also points out that we should really have a decorators_unittest.py method.

Also, if it turns out that we can't move the cache to the right spot, a better
way to get a unique ID would be id(args[0]).

+        except AttributeError:
+          pass
+
+      if hasattr(self, '__CacheUniqueId'):
+        key = self.__CacheUniqueId + key
+
     if key not in cache:
       cache[key] = obj(*args, **kwargs)
     return cache[key]