fix batch handling

for some reason there are two timeouts. in the batch scenario,
all the time wasted waiting on initial 'get' is never accounted
for so the batch timeout is always longer than it is declared.

Change-Id: I6132c770cccdf0ffad9f178f7463288cf954d672

oslo_messaging/_drivers/base.py

@@ -46,27 +46,15 @@ def batch_poll_helper(func):
         driver_prefetch = in_self.prefetch_size
         if driver_prefetch > 0:
             batch_size = min(batch_size, driver_prefetch)
+        timeout = batch_timeout or timeout
 
-        with timeutils.StopWatch(timeout) as timeout_watch:
-            # poll first message
-            msg = func(in_self, timeout=timeout_watch.leftover(True))
-            if msg is not None:
-                incomings.append(msg)
-            if batch_size == 1 or msg is None:
-                return incomings
-
-            # update batch_timeout according to timeout for whole operation
-            timeout_left = timeout_watch.leftover(True)
-            if timeout_left is not None and (
-                    batch_timeout is None or timeout_left < batch_timeout):
-                batch_timeout = timeout_left
-
-        with timeutils.StopWatch(batch_timeout) as batch_timeout_watch:
-            # poll remained batch messages
-            while len(incomings) < batch_size and msg is not None:
-                msg = func(in_self, timeout=batch_timeout_watch.leftover(True))
-                if msg is not None:
-                    incomings.append(msg)
+        with timeutils.StopWatch(timeout) as watch:
+            while True:
+                message = func(in_self, timeout=watch.leftover(True))
+                if message is not None:
+                    incomings.append(message)
+                if len(incomings) == batch_size or message is None:
+                    break
 
         return incomings
     return wrapper