Merge _find_coordinator_id methods

Previously there were two methods:
* `_find_coordinator_id()`
* `_find_many_coordinator_ids()`

But they do basically the same thing internally. And we need the plural
two places, but the singular only one place.

So merge them, and change the function signature to take a list of
`group_ids` and return a dict of `group_id: coordinator_id`s.

As a result of this, the `describe_groups()` command should scale better
because the `_find_coordinator_ids()` command issues all the requests
async, instead of sequentially blocking as the `described_groups()` used
to do.

Author: jeffwidman

kafka/admin/client.py

@@ -328,43 +328,27 @@ def _find_coordinator_id_process_response(self, response):
                 .format(response.API_VERSION))
         return response.coordinator_id
 
-    def _find_coordinator_id(self, group_id):
-        """Find the broker node_id of the coordinator of the given group.
-
-        Sends a FindCoordinatorRequest message to the cluster. Will block until
-        the FindCoordinatorResponse is received. Any errors are immediately
-        raised.
-
-        :param group_id: The consumer group ID. This is typically the group
-            name as a string.
-        :return: The node_id of the broker that is the coordinator.
-        """
-        future = self._find_coordinator_id_send_request(group_id)
-        self._wait_for_futures([future])
-        response = future.value
-        return self._find_coordinator_id_process_response(response)
-
-    def _find_many_coordinator_ids(self, group_ids):
-        """Find the broker node_id of the coordinator for each of the given groups.
+    def _find_coordinator_ids(self, group_ids):
+        """Find the broker node_ids of the coordinators of the given groups.
 
         Sends a FindCoordinatorRequest message to the cluster for each group_id.
         Will block until the FindCoordinatorResponse is received for all groups.
         Any errors are immediately raised.
 
         :param group_ids: A list of consumer group IDs. This is typically the group
             name as a string.
-        :return: A list of tuples (group_id, node_id) where node_id is the id
-            of the broker that is the coordinator for the corresponding group.
+        :return: A dict of {group_id: node_id} where node_id is the id of the
+            broker that is the coordinator for the corresponding group.
         """
-        futures = {
+        groups_futures = {
             group_id: self._find_coordinator_id_send_request(group_id)
             for group_id in group_ids
         }
-        self._wait_for_futures(list(futures.values()))
-        groups_coordinators = [
-            (group_id, self._find_coordinator_id_process_response(f.value))
-            for group_id, f in futures.items()
-        ]
+        self._wait_for_futures(groups_futures.values())
+        groups_coordinators = {
+            group_id: self._find_coordinator_id_process_response(future.value)
+            for group_id, future in groups_futures.items()
+        }
         return groups_coordinators
 
     def _send_request_to_node(self, node_id, request):
@@ -1094,18 +1078,19 @@ def describe_consumer_groups(self, group_ids, group_coordinator_id=None, include
             partition assignments.
         """
         group_descriptions = []
-        futures = []
-        for group_id in group_ids:
-            if group_coordinator_id is not None:
-                this_groups_coordinator_id = group_coordinator_id
-            else:
-                this_groups_coordinator_id = self._find_coordinator_id(group_id)
-            f = self._describe_consumer_groups_send_request(
+
+        if group_coordinator_id is not None:
+            groups_coordinators = {group_id: group_coordinator_id for group_id in group_ids}
+        else:
+            groups_coordinators = self.groups_coordinators(group_ids)
+
+        futures = [
+            self._describe_consumer_groups_send_request(
                 group_id,
-                this_groups_coordinator_id,
+                coordinator_id,
                 include_authorized_operations)
-            futures.append(f)
-
+            for group_id, coordinator_id in groups_coordinators.items()
+        ]
         self._wait_for_futures(futures)
 
         for future in futures:
@@ -1277,7 +1262,7 @@ def list_consumer_group_offsets(self, group_id, group_coordinator_id=None,
             explicitly specified.
         """
         if group_coordinator_id is None:
-            group_coordinator_id = self._find_coordinator_id(group_id)
+            group_coordinator_id = self._find_coordinator_ids([group_id])[group_id]
         future = self._list_consumer_group_offsets_send_request(
                                     group_id, group_coordinator_id, partitions)
         self._wait_for_futures([future])
@@ -1305,12 +1290,12 @@ def delete_consumer_groups(self, group_ids, group_coordinator_id=None):
         if group_coordinator_id is not None:
             futures = [self._delete_consumer_groups_send_request(group_ids, group_coordinator_id)]
         else:
-            groups_coordinators = defaultdict(list)
-            for group_id, group_coordinator_id in self._find_many_coordinator_ids(group_ids):
-                groups_coordinators[group_coordinator_id].append(group_id)
+            coordinators_groups = defaultdict(list)
+            for group_id, coordinator_id in self._find_coordinator_ids(group_ids).items():
+                coordinators_groups[coordinator_id].append(group_id)
             futures = [
-                self._delete_consumer_groups_send_request(group_ids, group_coordinator_id)
-                for group_coordinator_id, group_ids in groups_coordinators.items()
+                self._delete_consumer_groups_send_request(group_ids, coordinator_id)
+                for coordinator_id, group_ids in coordinators_groups.items()
             ]
 
         self._wait_for_futures(futures)