Implement waiting for all parties to ack snapshot before confirming it

input-output-hk · Jun 16, 2021 · abe3316 · abe3316
1 parent bf33662
commit abe3316
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Showing 3 changed files with 50 additions and 19 deletions.
diff --git a/hydra-node/src/Hydra/HeadLogic.hs b/hydra-node/src/Hydra/HeadLogic.hs
@@ -83,7 +83,7 @@ data HydraMessage tx
   | AckTx Party tx
   | ConfTx
   | ReqSn SnapshotNumber [tx]
-  | AckSn Party (Snapshot tx) -- TODO: should actually be stored locally and not transmitted
+  | AckSn Party SnapshotNumber
   | ConfSn
   | Ping Party
   deriving (Eq, Show)
@@ -127,6 +127,7 @@ data SimpleHeadState tx = SimpleHeadState
     unconfirmedTxs :: Map tx (Set Party)
   , confirmedTxs :: [tx]
   , confirmedSnapshot :: Snapshot tx
+  , unconfirmedSnapshot :: Maybe (Snapshot tx, Set Party)
   }
 
 deriving instance Tx tx => Eq (SimpleHeadState tx)
@@ -217,7 +218,7 @@ update Environment{party, snapshotStrategy} ledger (HeadState p st) ev = case (s
     let u0 = utxo
      in newState
           p
-          (OpenState $ SimpleHeadState u0 mempty mempty (Snapshot 0 u0 mempty))
+          (OpenState $ SimpleHeadState u0 mempty mempty (Snapshot 0 u0 mempty) Nothing)
           [ClientEffect $ HeadIsOpen u0]
   --
   (OpenState SimpleHeadState{confirmedSnapshot, confirmedTxs}, ClientEvent Close) ->
@@ -271,21 +272,51 @@ update Environment{party, snapshotStrategy} ledger (HeadState p st) ev = case (s
               )
               []
   (OpenState s@SimpleHeadState{confirmedSnapshot}, NetworkEvent (ReqSn sn txs)) ->
+    -- TODO: Verify the request is signed by (?) / comes from the leader
+    -- (Can we prove a message comes from a given peer, without signature?)
     case applyTransactions ledger (utxo confirmedSnapshot) txs of
       Left e ->
+        --TODO: Wait for transaction to be applicable.
         panic $ "Received not applicable snapshot (" <> show sn <> ") " <> show txs <> ": " <> show e
-      Right u ->
-        let nextSnapshot = Snapshot sn u txs
-         in newState p (OpenState s) [NetworkEffect $ AckSn party nextSnapshot]
-  (OpenState headState@SimpleHeadState{confirmedTxs, confirmedSnapshot}, NetworkEvent (AckSn _otherParty sn))
-    | number confirmedSnapshot + 1 == number sn ->
-      -- TODO: wait for all AckSn before confirming!
-      newState
-        p
-        (OpenState $ headState{confirmedTxs = confirmedTxs \\ confirmed sn, confirmedSnapshot = sn})
-        [ClientEffect $ SnapshotConfirmed $ number sn]
-    | otherwise ->
-      newState p st []
+      Right u
+        | number confirmedSnapshot + 1 == sn ->
+          let nextSnapshot = Snapshot sn u txs
+           in newState
+                p
+                (OpenState $ s{unconfirmedSnapshot = Just (nextSnapshot, mempty)})
+                [NetworkEffect $ AckSn party sn]
+      Right _ ->
+        panic $ "Received invalid snapshot request from leader. Confirmed snapshot: " <> show (number confirmedSnapshot) <> ", Requested snapshot: " <> show sn
+  (OpenState headState@SimpleHeadState{confirmedTxs, unconfirmedSnapshot}, NetworkEvent (AckSn otherParty sn)) ->
+    -- TODO: Verify snapshot signatures.
+    case unconfirmedSnapshot of
+      Nothing -> panic "TODO: wait until reqSn is seen (and unconfirmedSnapshot created)"
+      Just (snapshot, sigs)
+        | number snapshot == sn ->
+          let sigs' = otherParty `Set.insert` sigs
+           in if sigs' == parties p
+                then
+                  newState
+                    p
+                    ( OpenState $
+                        headState
+                          { confirmedTxs = confirmedTxs \\ confirmed snapshot
+                          , confirmedSnapshot = snapshot
+                          , unconfirmedSnapshot = Nothing
+                          }
+                    )
+                    [ClientEffect $ SnapshotConfirmed sn]
+                else
+                  newState
+                    p
+                    ( OpenState $
+                        headState
+                          { unconfirmedSnapshot = Just (snapshot, sigs')
+                          }
+                    )
+                    []
+      Just (snapshot, _) ->
+        panic $ "Received ack for unknown unconfirmed snapshot. Unconfirmed snapshot: " <> show (number snapshot) <> ", Requested snapshot: " <> show sn
   (_, OnChainEvent (CloseTx snapshot txs)) ->
     -- TODO(1): Should check whether we want / can contest the close snapshot by
     --       comparing with our local state / utxo.

diff --git a/hydra-node/test/Hydra/HeadLogicSpec.hs b/hydra-node/test/Hydra/HeadLogicSpec.hs
@@ -51,7 +51,7 @@ spec = describe "Hydra Head Logic" $ do
 
   it "confirms tx given it receives AckTx from all parties" $ do
     let reqTx = NetworkEvent $ ReqTx (ValidTx 1)
-        ackFrom n = NetworkEvent $ AckTx n (ValidTx 1)
+        ackFrom p = NetworkEvent $ AckTx p (ValidTx 1)
         s0 = initialState threeParties ledger
 
     s1 <- assertNewState $ update env ledger s0 reqTx
@@ -68,7 +68,7 @@ spec = describe "Hydra Head Logic" $ do
   it "confirms snapshot given it receives AckSn from all parties" $ do
     let s0 = initialState threeParties ledger
         reqSn = NetworkEvent $ ReqSn 1 []
-        ackFrom n = NetworkEvent $ AckSn n (Snapshot 1 [] [])
+        ackFrom p = NetworkEvent $ AckSn p 1
     s1 <- assertNewState $ update env ledger s0 reqSn
     s2 <- assertNewState $ update env ledger s1 (ackFrom 3)
     s3 <- assertNewState $ update env ledger s2 (ackFrom 1)
@@ -100,7 +100,7 @@ genHeadStatus =
     [ InitState
     , FinalState
     , CollectingState mempty mempty
-    , OpenState (SimpleHeadState [] mempty mempty (Snapshot 0 mempty mempty))
+    , OpenState (SimpleHeadState [] mempty mempty (Snapshot 0 mempty mempty) Nothing)
     ]
 
 defaultHeadParameters :: HeadParameters
@@ -135,7 +135,7 @@ initialState parties Ledger{initUTxO} =
   let u0 = initUTxO
       snapshot0 = Snapshot 0 u0 mempty
    in HeadState
-        { headStatus = OpenState $ SimpleHeadState u0 mempty mempty snapshot0
+        { headStatus = OpenState $ SimpleHeadState u0 mempty mempty snapshot0 Nothing
         , headParameters =
             HeadParameters
               { contestationPeriod = 42

diff --git a/hydra-node/test/Hydra/NetworkSpec.hs b/hydra-node/test/Hydra/NetworkSpec.hs
@@ -91,7 +91,7 @@ instance Arbitrary (HydraMessage MockTx) where
       , AckTx <$> arbitraryNatural <*> arbitrary
       , pure ConfTx
       , ReqSn <$> arbitraryNatural <*> arbitrary
-      , AckSn <$> arbitraryNatural <*> arbitrary
+      , AckSn <$> arbitraryNatural <*> arbitraryNatural
       , pure ConfSn
       , Ping <$> arbitraryNatural
       ]