Merge ~blake-rouse/maas:get-all-rack-conns-2.2 into maas:2.2

[Blake Rouse]

Backport f0fa3535e30bf3d3a6a1c437e8f8199ac0bbfeb5: Return only one connection per rack controller from getAllClients. Fixes lp: #1704489.

[Blake Rouse (blake-rouse)]

Self-approving backport.

review: Approve

diff --git a/src/maasserver/rpc/regionservice.py b/src/maasserver/rpc/regionservice.py
index b622cfb..a68b038 100644
--- a/src/maasserver/rpc/regionservice.py
+++ b/src/maasserver/rpc/regionservice.py
@@ -965,11 +965,10 @@ class RegionService(service.Service, object):
 
     @asynchronous(timeout=FOREVER)
     def getAllClients(self):
-        """Return a list of all connected :class:`common.Client`s."""
+        """Return a list with one connection per rack controller."""
         return [
-            common.Client(conn)
+            common.Client(random.choice(list(conns)))
             for conns in self.connections.values()
-            for conn in conns
         ]
 
     @asynchronous(timeout=FOREVER)
diff --git a/src/maasserver/rpc/tests/test_regionservice.py b/src/maasserver/rpc/tests/test_regionservice.py
index 33b9678..e845b30 100644
--- a/src/maasserver/rpc/tests/test_regionservice.py
+++ b/src/maasserver/rpc/tests/test_regionservice.py
@@ -100,7 +100,9 @@ from testtools.matchers import (
     Is,
     IsInstance,
     MatchesAll,
+    MatchesAny,
     MatchesListwise,
+    MatchesSetwise,
     MatchesStructure,
     Not,
 )
@@ -884,10 +886,16 @@ class TestRegionService(MAASTestCase):
         c4 = DummyConnection()
         service.connections[uuid2].update({c3, c4})
         clients = service.getAllClients()
-        self.assertItemsEqual(clients, {
-            common.Client(c1), common.Client(c2),
-            common.Client(c3), common.Client(c4),
-        })
+        self.assertThat(list(clients), MatchesAny(
+            MatchesSetwise(
+                Equals(common.Client(c1)), Equals(common.Client(c3))),
+            MatchesSetwise(
+                Equals(common.Client(c1)), Equals(common.Client(c4))),
+            MatchesSetwise(
+                Equals(common.Client(c2)), Equals(common.Client(c3))),
+            MatchesSetwise(
+                Equals(common.Client(c2)), Equals(common.Client(c4))),
+        ))
 
     def test_addConnectionFor_adds_connection(self):
         service = RegionService(sentinel.advertiser)