Revert "fix for out of order events (#228)" (#232)

This reverts commit 7e3c60c

faust/transport/consumer.py

@@ -435,6 +435,7 @@ class Consumer(Service, ConsumerT):
 
     flow_active: bool = True
     can_resume_flow: Event
+    suspend_flow: Event
 
     def __init__(
         self,
@@ -475,6 +476,7 @@ def __init__(
         self._end_offset_monitor_interval = self.commit_interval * 2
         self.randomly_assigned_topics = set()
         self.can_resume_flow = Event()
+        self.suspend_flow = Event()
         self._reset_state()
         super().__init__(loop=loop or self.transport.loop, **kwargs)
         self.transactions = self.transport.create_transaction_manager(
@@ -497,6 +499,7 @@ def _reset_state(self) -> None:
         self._paused_partitions = set()
         self._buffered_partitions = set()
         self.can_resume_flow.clear()
+        self.suspend_flow.clear()
         self.flow_active = True
         self._time_start = monotonic()
 
@@ -573,11 +576,13 @@ def stop_flow(self) -> None:
         """Block consumer from processing any more messages."""
         self.flow_active = False
         self.can_resume_flow.clear()
+        self.suspend_flow.set()
 
     def resume_flow(self) -> None:
         """Allow consumer to process messages."""
         self.flow_active = True
         self.can_resume_flow.set()
+        self.suspend_flow.clear()
 
     def pause_partitions(self, tps: Iterable[TP]) -> None:
         """Pause fetching from partitions."""
@@ -1120,7 +1125,9 @@ async def _drain_messages(self, fetcher: ServiceT) -> None:  # pragma: no cover
                                 if self._n_acked >= commit_every:
                                     self._n_acked = 0
                                     await self.commit()
-                            await callback(message)
+                            await self.wait_first(
+                                callback(message), self.suspend_flow.wait()
+                            )
                             set_read_offset(tp, offset)
                         else:
                             self.log.dev(