Reliable tracing with Async exceptions

In promotedToWarmRemoteImpl (and family), it is possible that the STM action successfully commits, writing a new state to the connVar, but right after an AsyncCancelled is received making us omit the respective transition tracing.
IntersectMBO · Oct 12, 2021 · 5631f29 · 5631f29
1 parent 9478f2a
commit 5631f29
Showing 1 changed file with 7 additions and 4 deletions.
diff --git a/ouroboros-network-framework/src/Ouroboros/Network/ConnectionManager/Core.hs b/ouroboros-network-framework/src/Ouroboros/Network/ConnectionManager/Core.hs
@@ -1022,12 +1022,13 @@ withConnectionManager ConnectionManagerArguments {
                               (const $ Connected connId dataFlow handle)
                               mbTransition)
 
-
+    -- Needs 'mask' in order to guarantee that the traces are logged if the an
+    -- Async exception lands between the successful STM action and the logging action.
     unregisterInboundConnectionImpl
         :: StrictTMVar m (ConnectionManagerState peerAddr handle handleError version m)
         -> peerAddr
         -> m (OperationResult DemotedToColdRemoteTr)
-    unregisterInboundConnectionImpl stateVar peerAddr = do
+    unregisterInboundConnectionImpl stateVar peerAddr = mask_ $ do
       traceWith tracer (TrUnregisterConnection Inbound peerAddr)
       (mbThread, mbTransition, result) <- atomically $ do
         state <- readTMVar stateVar
@@ -1677,7 +1678,7 @@ withConnectionManager ConnectionManagerArguments {
                 -- @
                 --   DemotedToCold^{Duplex}_{Local}
                 --     : OutboundState Duplex
-                --     → InboundIdleState^\tau
+                --     → OutboundIdleState^\tau
                 -- @
                 let connState' = OutboundIdleState connId connThread handle
                                                    Duplex
@@ -1875,6 +1876,8 @@ withConnectionManager ConnectionManagerArguments {
           return (OperationSuccess a)
 
 
+    -- Needs 'mask' in order to guarantee that the traces are logged if the an
+    -- Async exception lands between the successful STM action and the logging action.
     promotedToWarmRemoteImpl
         :: StrictTMVar m (ConnectionManagerState peerAddr handle handleError version m)
         -> peerAddr
@@ -2043,7 +2046,7 @@ withConnectionManager ConnectionManagerArguments {
           -- - set the state to 'TerminatedState'
           traverse_ cancel pruneMap
 
-        _ -> return ()
+        _ -> pure ()
       return (abstractState . fromState <$> fst result)