belliottsmith commented on code in PR #7:
URL: https://github.com/apache/cassandra-accord/pull/7#discussion_r1013176402
##########
accord-core/src/main/java/accord/messages/Defer.java:
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@@ -0,0 +1,77 @@
+package accord.messages;
+
+import java.util.BitSet;
+import java.util.function.Function;
+
+import accord.local.*;
+import accord.primitives.TxnId;
+
+import static accord.local.PreLoadContext.contextFor;
+import static accord.messages.Defer.Ready.Expired;
+import static accord.messages.Defer.Ready.No;
+import static accord.messages.Defer.Ready.Yes;
+
+// TODO: use something more efficient? could probably assign each CommandStore
a unique ascending integer and use an int[]
+class Defer implements Listener
+{
+ public enum Ready { No, Yes, Expired }
+
+ final Function<Command, Ready> waitUntil;
+ final TxnRequest<?> request;
+ BitSet waitingOn = new BitSet(); // TODO: move to compressed integer hash
map to permit easier reclamation of ids
+ int waitingOnCount;
+ boolean isDone;
+
+ Defer(Status waitUntil, TxnRequest<?> request)
+ {
+ this(command -> {
+ int c = command.status().compareTo(waitUntil);
+ if (c < 0) return No;
+ if (c > 0) return Expired;
+ return Yes;
+ }, request);
+ }
+
+ Defer(Function<Command, Ready> waitUntil, TxnRequest<?> request)
+ {
+ this.waitUntil = waitUntil;
+ this.request = request;
+ }
+
+ void add(Command command, CommandStore commandStore)
+ {
+ if (isDone)
+ throw new IllegalStateException("Recurrent retry of " + request);
+
+ waitingOn.set(commandStore.id());
+ ++waitingOnCount;
+ command.addListener(this);
+ }
+
+ @Override
+ public void onChange(SafeCommandStore safeStore, Command command)
+ {
+ Ready ready = waitUntil.apply(command);
+ if (ready == No) return;
+ command.removeListener(this);
+ if (ready == Expired) return;
Review Comment:
If we've already committed, essentially. Though this can be simplified since
we only use it in the one place now, and actually I think this is broken given
our changed semantics for `Accept` that means we don't need to `PreAccept`
first. I've addressed this in a follow-up commit.
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