Neaten the handling of state and auth_chain up a bit

synapse/handlers/federation.py

@@ -30,6 +30,7 @@ from synapse.types import UserID
 
 from twisted.internet import defer
 
+import itertools
 import logging
 
 
@@ -112,14 +113,6 @@ class FederationHandler(BaseHandler):
 
         logger.debug("Event: %s", event)
 
-        event_ids = set()
-        if state:
-            event_ids |= {e.event_id for e in state}
-        if auth_chain:
-            event_ids |= {e.event_id for e in auth_chain}
-
-        seen_ids = (yield self.store.have_events(event_ids)).keys()
-
         # FIXME (erikj): Awful hack to make the case where we are not currently
         # in the room work
         current_state = None
@@ -131,9 +124,18 @@ class FederationHandler(BaseHandler):
             logger.debug("Got event for room we're not in.")
             current_state = state
 
+        event_ids = set()
+        if state:
+            event_ids |= {e.event_id for e in state}
+        if auth_chain:
+            event_ids |= {e.event_id for e in auth_chain}
+
+        seen_ids = (yield self.store.have_events(event_ids)).keys()
+
         if state and auth_chain is not None:
-            for list_of_pdus in [auth_chain, state]:
+            # If we have any state or auth_chain given to us by the replication
-                for e in list_of_pdus:
+            # layer, then we should handle them (if we haven't before.)
+            for e in itertools.chain(auth_chain, state):
                 if e.event_id in seen_ids:
                     continue
 
@@ -147,6 +149,7 @@ class FederationHandler(BaseHandler):
                     yield self._handle_new_event(
                         origin, e, auth_events=auth
                     )
+                    seen_ids.add(e.event_id)
                 except:
                     logger.exception(
                         "Failed to handle state event %s",