From ff34c7929a173881bd77d8e671b26857adfbba65 Mon Sep 17 00:00:00 2001
From: Sasha Bogicevic <sasha.bogicevic@iohk.io>
Date: Fri, 15 Sep 2023 17:35:57 +0200
Subject: [PATCH] Re-read acks upon sending

After possible callback local acks might change so we need to re-read
them from a TVar.

Add a party in the BroadcastCounter to improve logging.
---
 hydra-node/src/Hydra/Network/Reliability.hs | 45 +++++++++++----------
 1 file changed, 23 insertions(+), 22 deletions(-)

diff --git a/hydra-node/src/Hydra/Network/Reliability.hs b/hydra-node/src/Hydra/Network/Reliability.hs
index 51a06c0d2b3..f9d0ba5e574 100644
--- a/hydra-node/src/Hydra/Network/Reliability.hs
+++ b/hydra-node/src/Hydra/Network/Reliability.hs
@@ -122,7 +122,7 @@ withReliability tracer us allParties withRawNetwork callback action = do
               modifyTVar' sentMessages (`snoc` msg)
               readTVar ackCounter
 
-            traceWith tracer (BroadcastCounter ackCounter')
+            traceWith tracer (BroadcastCounter us ackCounter')
 
             broadcast $ Authenticated (Msg ackCounter' msg) us
         }
@@ -142,31 +142,32 @@ withReliability tracer us allParties withRawNetwork callback action = do
           atomically $ writeTVar ackCounter newAcks
           callback (Authenticated msg party)
 
+        -- read our local acks again since they might be updated above
+        existingAcks' <- readTVarIO ackCounter
         -- resend messages if party did not acknowledge our latest idx
         let myIndex = fromJust $ elemIndex us allParties
         let acked = acks ! myIndex
-        let latestMsgAck = (! myIndex) existingAcks
+        let latestMsgAck = (! myIndex) existingAcks'
         when (acked < latestMsgAck) $ do
           let missing = fromList [acked + 1 .. latestMsgAck]
-          traceWith tracer (Resending missing acks existingAcks party)
-          atomically $ do
-            messages <- readTVar sentMessages
-            forM_ missing $ \idx -> do
-              case messages !? (idx - 1) of
-                Nothing ->
-                  throwIO $
-                    ReliabilityFailedToFindMsg $
-                      "FIXME: this should never happen, there's no sent message at index "
-                        <> show idx
-                        <> ", messages length = "
-                        <> show (length messages)
-                        <> ", latest message ack: "
-                        <> show latestMsgAck
-                        <> ", acked: "
-                        <> show acked
-                Just missingMsg -> do
-                  let newAcks = zipWith (\ack i -> if i == myIndex then idx else ack) existingAcks partyIndexes
-                  resend $ Authenticated (Msg newAcks missingMsg) us
+          messages <- readTVarIO sentMessages
+          forM_ missing $ \idx -> do
+            case messages !? (idx - 1) of
+              Nothing ->
+                throwIO $
+                  ReliabilityFailedToFindMsg $
+                    "FIXME: this should never happen, there's no sent message at index "
+                      <> show idx
+                      <> ", messages length = "
+                      <> show (length messages)
+                      <> ", latest message ack: "
+                      <> show latestMsgAck
+                      <> ", acked: "
+                      <> show acked
+              Just missingMsg -> do
+                let newAcks' = zipWith (\ack i -> if i == myIndex then idx else ack) existingAcks' partyIndexes
+                traceWith tracer (Resending missing acks newAcks' party)
+                atomically $ resend $ Authenticated (Msg newAcks' missingMsg) us
 
   partyIndexes = generate (length allParties) id
 
@@ -175,7 +176,7 @@ withReliability tracer us allParties withRawNetwork callback action = do
 
 data ReliabilityLog
   = Resending {missing :: Vector Int, acknowledged :: Vector Int, localCounter :: Vector Int, party :: Party}
-  | BroadcastCounter {localCounter :: Vector Int}
+  | BroadcastCounter {party :: Party, localCounter :: Vector Int}
   deriving stock (Show, Eq, Generic)
   deriving anyclass (ToJSON, FromJSON)