Fix crash occurring when reorg message is the first one from TzKT (#232)

* Fix crash occurring when reorg message is the first one received by the datasource

* Changelog

Author: droserasprout

CHANGELOG.md

@@ -11,6 +11,7 @@ Please use [this](https://docs.gitlab.com/ee/development/changelog.html) documen
 * context: Fixed ignored `wait` argument of `fire_hook` method.
 * hasura: Fixed processing relation fields with missing `related_name`.
 * jobs: Fixed default `apscheduler` config.
+* tzkt: Fixed crash occurring when reorg message is the first one received by the datasource.
 
 ## 4.2.2 - 2022-02-01
 

src/dipdup/datasources/tzkt/datasource.py

@@ -683,12 +683,21 @@ async def _extract_message_data(self, type_: MessageType, message: List[Any]) ->
 
             # NOTE: Emit rollback, but not on `head` message
             elif tzkt_type == TzktMessageType.REORG:
-                if current_level is None:
-                    raise RuntimeError('Reorg message received but level is not set')
                 # NOTE: operation/big_map channels have their own levels
                 if type_ == MessageType.head:
                     return
 
+                # NOTE: If no data messages were received since run, use sync level instead
+                if current_level is None:
+                    # NOTE: There's only one sync level for all channels, otherwise `Index.process` would fail
+                    current_level = self.get_sync_level(HeadSubscription())
+                    if not current_level:
+                        raise RuntimeError('Reorg message received, but neither current nor sync level is known')
+
+                    # NOTE: This rollback does not affect us, so we can safely ignore it
+                    if current_level <= level:
+                        return
+
                 self._logger.info('Emitting rollback from %s to %s', current_level, level)
                 await self.emit_rollback(current_level, level)