Reduce AckSn spam (#2146)

Ignores valid `AckSn` messages in case we have seen the acknowledged
snapshot already as confirmed.

This was discovered when running so-called "mirror nodes" where a
counter-party runs multiple `hydra-node` instances with the same set of
keys.

---

* [x] CHANGELOG updated
* [x] Documentation update not needed
* [x] Haddocks update not needed
* [x] No new TODOs introduced

Author: noonio

hydra-node/hydra-node.cabal

@@ -1,6 +1,6 @@
 cabal-version:      3.0
 name:               hydra-node
-version:            0.22.2
+version:            0.22.4
 synopsis:           The Hydra node
 author:             IOG
 copyright:          2022 IOG

hydra-node/src/Hydra/HeadLogic.hs

@@ -647,6 +647,11 @@ onOpenNetworkAckSn Environment{party} openState otherParty snapshotSignature sn
 
   waitOnSeenSnapshot continue =
     case seenSnapshot of
+      -- NOTE: Ignore any redundant AckSn for snapshots we have already seen as
+      -- confirmed. This is for example happening if a party runs multiple
+      -- instances of hydra-node using the same keys.
+      LastSeenSnapshot{lastSeen}
+        | sn <= lastSeen -> noop
       SeenSnapshot snapshot sigs
         | seenSn == sn -> continue snapshot sigs
       _ -> wait WaitOnSeenSnapshot

hydra-node/test/Hydra/HeadLogicSpec.hs

@@ -46,6 +46,7 @@ import Hydra.HeadLogic (
   WaitReason (..),
   aggregateState,
   cause,
+  noop,
   update,
  )
 import Hydra.HeadLogic.State (SeenSnapshot (..), getHeadParameters)
@@ -63,7 +64,7 @@ import Hydra.Tx.Crypto (aggregate, generateSigningKey, sign)
 import Hydra.Tx.Crypto qualified as Crypto
 import Hydra.Tx.HeadParameters (HeadParameters (..))
 import Hydra.Tx.IsTx (IsTx (..))
-import Hydra.Tx.Party (Party (..))
+import Hydra.Tx.Party (Party (..), deriveParty)
 import Hydra.Tx.Snapshot (ConfirmedSnapshot (..), Snapshot (..), SnapshotNumber, SnapshotVersion, getSnapshot)
 import Test.Hydra.Node.Fixture qualified as Fixture
 import Test.Hydra.Tx.Fixture (alice, aliceSk, bob, bobSk, carol, carolSk, deriveOnChainId, testHeadId, testHeadSeed)
@@ -397,6 +398,21 @@ spec =
             Error (RequireFailed SnapshotAlreadySigned{receivedSignature}) -> receivedSignature == carol
             _ -> False
 
+      it "ignores valid AckSn if snapshot already confirmed" $ do
+        let reqSn = receiveMessage $ ReqSn 0 1 [] Nothing Nothing
+            snapshot1 = Snapshot testHeadId 0 1 [] mempty Nothing Nothing
+            ackFrom sk = receiveMessageFrom (deriveParty sk) $ AckSn (sign sk snapshot1) 1
+
+        s0 <- runHeadLogic bobEnv ledger (inOpenState threeParties) $ do
+          step reqSn
+          step (ackFrom carolSk)
+          step (ackFrom bobSk)
+          step (ackFrom aliceSk)
+          getState
+
+        update bobEnv ledger s0 (ackFrom carolSk)
+          `shouldBe` noop
+
       it "rejects snapshot request with transaction not applicable to previous snapshot" $ do
         let reqTx42 = receiveMessage $ ReqTx (SimpleTx 42 mempty (utxoRef 1))
             reqTx1 = receiveMessage $ ReqTx (SimpleTx 1 (utxoRef 1) (utxoRef 2))