Subreddit._by_name: Set 1 hour cache TTL

In the case of cache outages the values in cache can become out of
sync with reality. If a subreddit is created during an outage it will
be impossible to access it with Subreddit._by_name until the cache is
corrected. Setting a TTL will ensure this happens eventually.

r2/r2/models/subreddit.py

@@ -476,7 +476,11 @@ class Subreddit(Thing, Printable, BaseSite):
                     still_missing = set(srnames) - set(fetched)
                     fetched.update((name, cls.SRNAME_NOTFOUND) for name in still_missing)
                     try:
-                        g.gencache.set_multi(fetched, prefix='srid:')
+                        g.gencache.set_multi(
+                            keys=fetched,
+                            prefix='srid:',
+                            time=3600,
+                        )
                     except MemcachedError:
                         pass
 

r2/r2/tests/unit/models/subreddit_test.py

@@ -226,7 +226,10 @@ class ByNameTest(unittest.TestCase):
 
         self.assertEqual(ret, sr)
         self.cache.set_multi.assert_called_once_with(
-            {sr.name: sr._id}, prefix="srid:")
+            keys={sr.name: sr._id},
+            prefix="srid:",
+            time=3600,
+        )
 
     def testCacheNegativeResults(self):
         self.cache.get_multi.return_value = {}
@@ -237,7 +240,10 @@ class ByNameTest(unittest.TestCase):
             Subreddit._by_name("doesnotexist")
 
         self.cache.set_multi.assert_called_once_with(
-            {"doesnotexist": Subreddit.SRNAME_NOTFOUND}, prefix="srid:")
+            keys={"doesnotexist": Subreddit.SRNAME_NOTFOUND},
+            prefix="srid:",
+            time=3600,
+        )
 
     def testExcludeNegativeLookups(self):
         self.cache.get_multi.return_value = {"doesnotexist": Subreddit.SRNAME_NOTFOUND}