belliottsmith commented on a change in pull request #1:
URL: https://github.com/apache/cassandra-accord/pull/1#discussion_r757596322
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File path: accord-core/src/main/java/accord/local/Node.java
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@@ -116,37 +165,43 @@ public Timestamp uniqueNow()
return now.updateAndGet(cur -> {
// TODO: this diverges from proof; either show isomorphism or make
consistent
long now = nowSupplier.getAsLong();
- if (now > cur.real) return new Timestamp(now, 0, id);
- else return new Timestamp(cur.real, cur.logical + 1, id);
+ long epoch = Math.max(cur.epoch, topology.epoch());
+ return (now > cur.real)
+ ? new Timestamp(epoch, now, 0, id)
+ : new Timestamp(epoch, cur.real, cur.logical + 1, id);
});
}
public Timestamp uniqueNow(Timestamp atLeast)
{
if (now.get().compareTo(atLeast) < 0)
- now.accumulateAndGet(atLeast, (a, b) -> a.compareTo(b) < 0 ? new
Timestamp(b.real, b.logical + 1, id) : a);
-
- return now.updateAndGet(cur -> {
- // TODO: this diverges from proof; either show isomorphism or make
consistent
- long now = nowSupplier.getAsLong();
- if (now > cur.real) return new Timestamp(now, 0, id);
- else return new Timestamp(cur.real, cur.logical + 1, id);
- });
+ now.accumulateAndGet(atLeast, (current, proposed) -> {
+ Timestamp timestamp = proposed.compareTo(current) <= 0
+ ? new Timestamp(current.epoch, current.real,
current.logical + 1, id)
+ : proposed;
+ return timestamp.withMinEpoch(topology.epoch());
Review comment:
Could we just return `proposed.compareTo(current) <= 0 ? new
Timestamp(max(current.epoch, proposed.epoch), max(current.real, proposed.real),
current.logical + 1, id) : proposed;`?
Then we could call `uniqueNow` on witnessing a new epoch with `new
Timestamp(epoch, 0, 0, id)` and it should take care of itself without polling
this value on each update? We probably anyway want to ensure we don't go back
in `real` time so we don't mess up any timestamps we'll generate for Cassandra
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