Use QueryTip for local state queries

CHANGELOG.md

@@ -10,6 +10,11 @@ changes.
 
 ## [0.13.0] - UNRELEASED
 
+- Added retries for local cardano-node queries. We witnessed these queries to
+  fail in case of a rollback so we ignore errors and retry for 5 times before
+  letting the query fail.
+
+
 - **BREAKING** Changes to `hydra-plutus` scripts.
 
 - Add option to draft a commit tx using inline datums.

hydra-node/src/Hydra/Chain/CardanoClient.hs

@@ -9,6 +9,7 @@ import Hydra.Prelude
 import Hydra.Cardano.Api hiding (Block)
 
 import qualified Cardano.Api.UTxO as UTxO
+import Control.Tracer (showTracing, stdoutTracer, traceWith)
 import qualified Data.Set as Set
 import Ouroboros.Consensus.HardFork.Combinator.AcrossEras (EraMismatch)
 import Test.QuickCheck (oneof)
@@ -317,12 +318,23 @@ queryStakePools networkId socket queryPoint =
    in runQuery networkId socket queryPoint query >>= throwOnEraMismatch
 
 -- | Throws at least 'QueryException' if query fails.
+-- We don't expect the query to fail but this can easily happen in case of a
+-- rollback. So what we do is retry 5 times and then give up.
 runQuery :: NetworkId -> SocketPath -> QueryPoint -> QueryInMode CardanoMode a -> IO a
 runQuery networkId socket point query =
-  queryNodeLocalState (localNodeConnectInfo networkId socket) maybePoint query >>= \case
-    Left err -> throwIO $ QueryAcquireException err
-    Right result -> pure result
+  let tracer = traceWith $ showTracing stdoutTracer
+   in go tracer 5
  where
+  go tracer n =
+    queryNodeLocalState (localNodeConnectInfo networkId socket) maybePoint query >>= \case
+      Left err ->
+        if n == (0 :: Int)
+          then throwIO $ QueryAcquireException err
+          else do
+            tracer ("Retrying query... " ++ show n <> " Query: " <> show query)
+            threadDelay 1000000
+            go tracer (n - 1)
+      Right result -> pure result
   maybePoint =
     case point of
       QueryTip -> Nothing