[GitHub] [cassandra-accord] belliottsmith commented on a diff in pull request #50: State Eviction

["belliottsmith (via GitHub)" <gi...@apache.org>]

belliottsmith commented on code in PR #50:
URL: https://github.com/apache/cassandra-accord/pull/50#discussion_r1282351956


##########
accord-core/src/main/java/accord/local/CommandStores.java:
##########
@@ -87,44 +88,30 @@ private static class StoreSupplier
             this.shardFactory = shardFactory;
         }
 
-        CommandStore create(int id, RangesForEpochHolder rangesForEpoch)
+        CommandStore create(int id, EpochUpdateHolder rangesForEpoch)
         {
             return shardFactory.create(id, time, agent, this.store, progressLogFactory, rangesForEpoch);
         }
     }
 
-    public static class RangesForEpochHolder
-    {
-        // no need for safe publication; RangesForEpoch members are final, and will be guarded by other synchronization actions
-        protected RangesForEpoch current;
-
-        /**
-         * This is updated asynchronously, so should only be fetched between executing tasks;
-         * otherwise the contents may differ between invocations for the same task.
-         * @return the current RangesForEpoch
-         */
-        public RangesForEpoch get() { return current; }
-    }
-
     static class ShardHolder
     {
         final CommandStore store;
-        final RangesForEpochHolder ranges;
+        RangesForEpoch ranges;

Review Comment:
   The idea actually was that we would avoid changing the data we were looking at for an in-flight operation. But now that I look at this I think we need a stronger guarantee: we need to ensure command processing is deterministic for the work @iamaleksey is doing, so we need to ensure that anything we ask for here is the same as would be returned with *more* information. But that's slightly off-topic. It is very deliberate that we return "stale" information for a command that began processing with that information to hand.



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