session.py: close sessions hitting the hard limit

electrumx/server/session.py

@@ -234,11 +234,15 @@ class SessionManager(object):
         session_class = self.env.coin.SESSIONCLS
         while True:
             await sleep(100)
+            async with TaskGroup() as group:
                 for session in sorted(self.sessions, key=lambda s: s.cost, reverse=True):
                     # Subs have an on-going cost so decay more slowly with more subs
                     session.cost_decay_per_sec = (
                         session_class.cost_hard_limit / (10000 + 5 * session.sub_count()))
+                    try:
                         session.recalc_concurrency()
+                    except FinalRPCError:
+                        await group.spawn(session.close())
 
     def _get_info(self):
         '''A summary of server state.'''