Bulk fetch offset partitions in base consumer -- suggested by ecanzonieri

kafka/consumer/base.py

@@ -83,12 +83,13 @@ class Consumer(object):
         if not partitions:
             partitions = self.client.get_partition_ids_for_topic(self.topic)
 
-        for partition in partitions:
-            (resp,) = self.client.send_offset_fetch_request(
-                self.group,
-                [OffsetFetchRequest(self.topic, partition)],
-                fail_on_error=False
-            )
+        responses = self.client.send_offset_fetch_request(
+            self.group,
+            [OffsetFetchRequest(self.topic, p) for p in partitions],
+            fail_on_error=False
+        )
+
+        for resp in responses:
             try:
                 check_error(resp)
             # API spec says server wont set an error here
@@ -98,12 +99,12 @@ class Consumer(object):
 
             # -1 offset signals no commit is currently stored
             if resp.offset == -1:
-                self.offsets[partition] = 0
+                self.offsets[resp.partition] = 0
 
             # Otherwise we committed the stored offset
             # and need to fetch the next one
             else:
-                self.offsets[partition] = resp.offset
+                self.offsets[resp.partition] = resp.offset
 
     def commit(self, partitions=None):
         """