Add support for using keyword arguments with cached functions

1 files changed, 34 insertions, 6 deletions

diff --git a/synapse/storage/_base.py b/synapse/storage/_base.py
index 8f812f0fd7..f1265541ba 100644
--- a/synapse/storage/_base.py
+++ b/synapse/storage/_base.py
@@ -27,6 +27,7 @@ from twisted.internet import defer
 from collections import namedtuple, OrderedDict
 
 import functools
+import inspect
 import sys
 import time
 import threading
@@ -141,13 +142,28 @@ class CacheDescriptor(object):
     which can be used to insert values into the cache specifically, without
     calling the calculation function.
     """
-    def __init__(self, orig, max_entries=1000, num_args=1, lru=False):
+    def __init__(self, orig, max_entries=1000, num_args=1, lru=False,
+                 inlineCallbacks=False):
         self.orig = orig
 
+        if inlineCallbacks:
+            self.function_to_call = defer.inlineCallbacks(orig)
+        else:
+            self.function_to_call = orig
+
         self.max_entries = max_entries
         self.num_args = num_args
         self.lru = lru
 
+        self.arg_names = inspect.getargspec(orig).args[1:num_args+1]
+
+        if len(self.arg_names) < self.num_args:
+            raise Exception(
+                "Not enough explicit positional arguments to key off of for %r."
+                " (@cached cannot key off of *args or **kwars)"
+                % (orig.__name__,)
+            )
+
     def __get__(self, obj, objtype=None):
         cache = Cache(
             name=self.orig.__name__,
@@ -158,11 +174,13 @@ class CacheDescriptor(object):
 
         @functools.wraps(self.orig)
         @defer.inlineCallbacks
-        def wrapped(*keyargs):
+        def wrapped(*args, **kwargs):
+            arg_dict = inspect.getcallargs(self.orig, obj, *args, **kwargs)
+            keyargs = [arg_dict[arg_nm] for arg_nm in self.arg_names]
             try:
-                cached_result = cache.get(*keyargs[:self.num_args])
+                cached_result = cache.get(*keyargs)
                 if DEBUG_CACHES:
-                    actual_result = yield self.orig(obj, *keyargs)
+                    actual_result = yield self.function_to_call(obj, *args, **kwargs)
                     if actual_result != cached_result:
                         logger.error(
                             "Stale cache entry %s%r: cached: %r, actual %r",
@@ -177,9 +195,9 @@ class CacheDescriptor(object):
                 # while the SELECT is executing (SYN-369)
                 sequence = cache.sequence
 
-                ret = yield self.orig(obj, *keyargs)
+                ret = yield self.function_to_call(obj, *args, **kwargs)
 
-                cache.update(sequence, *keyargs[:self.num_args] + (ret,))
+                cache.update(sequence, *(keyargs + [ret]))
 
                 defer.returnValue(ret)
 
@@ -201,6 +219,16 @@ def cached(max_entries=1000, num_args=1, lru=False):
     )
 
 
+def cachedInlineCallbacks(max_entries=1000, num_args=1, lru=False):
+    return lambda orig: CacheDescriptor(
+        orig,
+        max_entries=max_entries,
+        num_args=num_args,
+        lru=lru,
+        inlineCallbacks=True,
+    )
+
+
 class LoggingTransaction(object):
     """An object that almost-transparently proxies for the 'txn' object
     passed to the constructor. Adds logging and metrics to the .execute()