Adds Event::SetRetired to validator-sets.
Emit TributaryRetired.
Replaces is_active_set, which made multiple network requests, with
is_retired_tributary, a DB read.
Performs most of the removals necessary upon TributaryRetired.
Still needs to clean up the actual Tributary/Tendermint tasks.
* Revert "Correct the prior documented TOCTOU"
This reverts commit d50fe87801.
* Correct the prior documented TOCTOU
d50fe87801 edited the challenge for the Batch to
fix it. This won't produce Batch n+1 until Batch n is successfully published
and verified. It's an alternative strategy able to be reviewed, with a much
smaller impact to scope.
The new set publishing a `Batch` completes the handover protocol. The new set
should only publish a `Batch` once it believes the old set has completed all of
its on-external-chain activity, marking it honest and finite.
With the handover comes the acceptance of liability, hence the requirement for
all of the on-Serai-chain activity also needing verification. While most
activity would be verified in-real-time (upon ::Batch messages), the new set
will now explicitly verify the complete set of `Batch`s before beginning its
preprocess for its own `Batch` (the one accepting the handover).
Renames Update to SignedBatch.
Checks Batch equality via a hash of the InInstructions. That prevents needing
to keep the Batch in node state or TX introspect.
This is a possibility under the new deterministic nonce scheme.
While there is a concern of us never creating a transaction with a nonce,
blocking everything, we should always create transactions. We'll always publish
preprocesses, and while we'll only publish shares if everyone else does, we
only allocate for shares once everyone else does.
The initial TODO was simply to use one ExternalBlock per all batches in the
block. This would require publishing ExternalBlock after the last batch,
requiring knowing the last batch. While we could add such a pipeline, it'd
require:
1) Initial preprocesses using a distinct message from BatchPreprocess
2) An additional message sent after all BatchPreprocess are sent
Unfortunately, both would require tweaks to the SubstrateSigner which aren't
worth the complexity compared to the solution here, at least, not at this time.
While this will cause, if a Tributary is signing a block whose total batch data
exceeds 25 kB, to use multiple transactions which could be optimized out by
'better' local data pipelining, that's an extreme edge case. Given the temporal
nature of each Tributary, it's also an acceptable edge.
This does no longer achieve synchrony over external blocks accordingly. While
signed batches have synchrony, as they embed their block hash, batches being
signed don't have cryptographic synchrony on their contents. This means
validators who are eclipsed may produce invalid shares, as they sign a
different batch. This will be introduced in a follow-up commit.
add_active_tributary writes the spec to disk before it returns, so even if the
VecDeque it pushes to isn't popped, the tributary will still be loaded on boot.
