fix: improve chain rollback handling for cached headers (#788)

Fixes #787

Signed-off-by: Aurora Gaffney <[email protected]>

Author: agaffney

chain/chain.go

@@ -220,15 +220,22 @@ func (c *Chain) Rollback(point ocommon.Point) error {
 	}
 	// Check headers for rollback point
 	if len(c.headers) > 0 {
-		for idx, header := range c.headers {
+		// Iterate backwards to make deletion safe
+		var header ledger.BlockHeader
+		for i := len(c.headers) - 1; i >= 0; i-- {
+			header = c.headers[i]
+			// Remove headers after rollback slot
+			if header.SlotNumber() > point.Slot {
+				c.headers = slices.Delete(c.headers, i, i+1)
+				continue
+			}
 			if header.SlotNumber() == point.Slot &&
 				string(header.Hash().Bytes()) == string(point.Hash) {
-				// Remove headers after rollback point
-				if idx < len(c.headers)-1 {
-					c.headers = slices.Delete(c.headers, idx+1, len(c.headers))
-				}
 				return nil
 			}
+			if header.SlotNumber() < point.Slot {
+				return ErrBlockNotFound
+			}
 		}
 	}
 	// Lookup block for rollback point

ledger/chainsync.go

@@ -137,16 +137,7 @@ func (ls *LedgerState) handleEventChainsyncBlockHeader(e ChainsyncEvent) error {
 	}
 	// Add header to chain
 	if err := ls.chain.AddBlockHeader(e.BlockHeader); err != nil {
-		if !errors.As(err, &chain.BlockNotFitChainTipError{}) {
-			return fmt.Errorf("failed adding chain block header: %w", err)
-		}
-		ls.config.Logger.Warn(
-			fmt.Sprintf(
-				"ignoring chainsync block header: %s",
-				err,
-			),
-		)
-		return nil
+		return fmt.Errorf("failed adding chain block header: %w", err)
 	}
 	// Wait for additional block headers before fetching block bodies if we're
 	// far enough out from upstream tip