Fix update bug in ets_lru

Previously, when an existing cache entry was updated, we didn't update the
atime. Subsequently, when the entry was removed, we never cleaned the orphan
atime entry. During trimming, we traverse the atime entries, and since the
orphaned one didn't have any matching objects or ctime entries, the ets_lru
cache would crash, possibly taking down the primary couch supervisor.

src/ets_lru/src/ets_lru.erl

@@ -167,8 +167,9 @@ handle_call({insert, Key, Val}, _From, St) ->
     Pattern = #entry{key = Key, atime = '$1', _ = '_'},
     case ets:match(St#st.objects, Pattern) of
         [[ATime]] ->
-            Update = {#entry.val, Val},
-            true = ets:update_element(St#st.objects, Key, Update),
+            true = ets:update_element(St#st.objects, Key, [
+                {#entry.val, Val}, {#entry.atime, NewATime}
+            ]),
             true = ets:delete(St#st.atimes, ATime),
             true = ets:insert(St#st.atimes, {NewATime, Key});
         [] ->

src/ets_lru/test/ets_lru_test.erl

@@ -132,6 +132,34 @@ basic_behavior_test_() ->
                             ?_assertEqual(not_found, ets_lru:lookup(LRU, foo))
                         }
                     ]
+                end,
+                fun({ok, LRU}) ->
+                    [
+                        {
+                            "Insert the value twice",
+                            ?_assertEqual(ok, ets_lru:insert(LRU, foo, bar))
+                        },
+                        {
+                            "Objects table size should be 1",
+                            ?_assertEqual(1, ets:info(test_lru_objects, size))
+                        },
+                        {
+                            "ATimes table size should be 1",
+                            ?_assertEqual(1, ets:info(test_lru_atimes, size))
+                        },
+                        {
+                            "CTimes table size should be 1",
+                            ?_assertEqual(1, ets:info(test_lru_ctimes, size))
+                        },
+                        {
+                            "Clear LRU after duplicate insert",
+                            ?_assertEqual(ok, ets_lru:clear(LRU))
+                        },
+                        {
+                            "Lookup returned not_found after a clear after a duplicate insert",
+                            ?_assertEqual(not_found, ets_lru:lookup(LRU, foo))
+                        }
+                    ]
                 end
             ]}
     }.