dcapwell commented on code in PR #38:
URL: https://github.com/apache/cassandra-accord/pull/38#discussion_r1177151414
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accord-core/src/main/java/accord/local/CommandStore.java:
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@@ -43,7 +48,88 @@ CommandStore create(int id,
RangesForEpochHolder rangesForEpoch);
}
+ @VisibleForTesting
+ class Unsafe
Review Comment:
> Should this be in the InMemoryCommandStore
Not really... If we are working with `CommandStore` we need the API to be
present there.
`Unsafe` has 2 things going on:
1) holds the reference to the `ThreadLocal` pointing to the `current`
`CommandStore`.
2) operations for tests to mutate the `ThreadLocal` that maybe "unsafe"
I tried to limit the scope of the `ThreadLocal` reference to make access
limited to only the "approved" methods, that was an attempt to limit bugs.
Now, for the Unsafe operations (num 2), those are used by more than
`InMemoryCommandStore`; current usages are
1) `accord.topology.TopologyManager#awaitEpoch` - Need to know if running
in a `CommandStore` or not, so we don't return a `AsyncChain` using the wrong
store
2) `accord.local.Node#checkStore` - makes sure that the selected
`CommandStore` is the current one; this has been critical to make sure that we
don't do the wrong thing.
3) `Synchronized` and `DelayedCommandStores` - since no threading is done,
this is to support the interleaving of tasks, which may be running in different
`CommandStore`s.
For 1/2 we just need access to `current` that *does not* fail, I left this
in `Unsafe` to at least denote that you must be careful, and to try to avoid
the wrong code paths calling it... this "could" be moved outside of `Unsafe`,
but then I would likely rename to `CommandStore.unsafeMaybeCurrent` or
something (just trying to denote not to call it)
for 3, I "could" try to limit this to `InMemoryCommandStore`, but I would
need to expose `register` and `remove`; that or have to make the `ThreadLocal`
public, which I was trying to avoid
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