Detect and rollback orphaned blocks

Orphan blocks occur when a new block does not extend the chain with the
most recent block in the database, but extends it with a block before
the most recent one. In this case we want to remove the orphaned blocks
before adding the new one.

Author: erikd

cardano-db-sync/src/Cardano/DbSync/Plugin/Default/Byron/Insert.hs

@@ -102,7 +102,17 @@ insertABlock
     -> ExceptT DbSyncNodeError (ReaderT SqlBackend m) ()
 insertABlock tracer blk tip = do
     meta <- liftLookupFail "insertABlock" DB.queryMeta
-    pbid <- liftLookupFail "insertABlock" $ DB.queryBlockId (Byron.unHeaderHash $ Byron.blockPreviousHash blk)
+
+    (pbid, mBlock) <- liftLookupFail "insertABOBBoundary" $
+                        DB.queryBlockIdAndNo (Byron.unHeaderHash $ Byron.blockPreviousHash blk)
+    case mBlock of
+      Nothing -> pure () -- Previous was an EBB
+      Just blockNo ->
+        if blockNo < Byron.blockNumber blk
+          then pure ()
+          else do
+            liftIO . logInfo tracer $ "Rollback orphan block number " <> textShow blockNo
+            lift . void $ DB.deleteCascadeBlockNo blockNo
 
     let slotsPerEpoch = 10 * DB.metaProtocolConst meta
 

cardano-db/src/Cardano/Db/Delete.hs

@@ -1,5 +1,6 @@
 module Cardano.Db.Delete
   ( deleteCascadeBlock
+  , deleteCascadeBlockNo
   , deleteCascadeSlotNo
   ) where
 
@@ -23,6 +24,14 @@ deleteCascadeBlock block = do
   mapM_ (deleteCascade . entityKey) keys
   pure $ not (null keys)
 
+-- | Delete a block if it exists. Returns 'True' if it did exist and has been
+-- deleted and 'False' if it did not exist.
+deleteCascadeBlockNo :: MonadIO m => Word64 -> ReaderT SqlBackend m Bool
+deleteCascadeBlockNo blockNo = do
+  keys <- selectList [ BlockBlockNo ==. Just blockNo ] []
+  mapM_ (deleteCascade . entityKey) keys
+  pure $ not (null keys)
+
 -- | Delete a block if it exists. Returns 'True' if it did exist and has been
 -- deleted and 'False' if it did not exist.
 deleteCascadeSlotNo :: MonadIO m => Word64 -> ReaderT SqlBackend m Bool

cardano-db/src/Cardano/Db/Query.hs

@@ -9,6 +9,7 @@ module Cardano.Db.Query
   , queryBlockCount
   , queryBlockHeight
   , queryBlockId
+  , queryBlockIdAndNo
   , queryBlockNo
   , queryMainBlock
   , queryBlockTxCount
@@ -115,6 +116,17 @@ queryBlockId hash = do
             pure $ blk ^. BlockId
   pure $ maybeToEither (DbLookupBlockHash hash) unValue (listToMaybe res)
 
+-- | Get the 'BlockId' and the 'BlockNo' associated with the given hash.
+-- This is is usually used with the prevHash for a block so that the back reference
+-- for the block can be obtained. The BlockNo is also returned so any orphaned blocks
+-- can be rolled back.
+queryBlockIdAndNo :: MonadIO m => ByteString -> ReaderT SqlBackend m (Either LookupFail (BlockId, Maybe Word64))
+queryBlockIdAndNo hash = do
+  res <- select . from $ \ blk -> do
+            where_ (blk ^. BlockHash ==. val hash)
+            pure $ (blk ^. BlockId, blk ^. BlockBlockNo)
+  pure $ maybeToEither (DbLookupBlockHash hash) unValue2 (listToMaybe res)
+
 queryBlockNo :: MonadIO m => Word64 -> ReaderT SqlBackend m (Maybe Block)
 queryBlockNo blkNo = do
   res <- select . from $ \ blk -> do