set-weight/remove-devices actions are leader-only

When running set-weight and remove-devices actions, they must be run
on the leader of the swift-proxy cluster.  Lacking this validation,
the ring builder file on a non-leader would get updated, but the
balance_rings action would fail, and the changes to the ring files
would not propogate to the remainder of the swift cluster.

Change-Id: I9134eb88b16e5ffe18f16ce30e03e469027b6670
Closes-Bug: 1882250

actions/actions.py

@@ -44,6 +44,9 @@ from charmhelpers.core.hookenv import (
     action_get,
     action_set,
 )
+from charmhelpers.contrib.hahelpers.cluster import (
+    is_elected_leader,
+)
 from charmhelpers.contrib.openstack.utils import (
     set_unit_paused,
     clear_unit_paused,
@@ -56,6 +59,7 @@ from lib.swift_utils import (
     services,
     set_weight_in_ring,
     SWIFT_CONF_DIR,
+    SWIFT_HA_RES,
 )
 
 
@@ -133,6 +137,10 @@ def remove_devices(args):
     :raises SwiftProxyCharmException: if pattern action_get('search-value')
         doesn't match any device in the ring.
     """
+    if not is_elected_leader(SWIFT_HA_RES):
+        action_fail('Must run action on leader unit')
+        return
+
     rings_valid = ['account', 'container', 'object', 'all']
     rings_to_update = []
     ring = action_get('ring')
@@ -160,6 +168,10 @@ def set_weight(args):
     :raises SwiftProxyCharmException: if pattern action_get('search-value')
         doesn't match any device in the ring.
     """
+    if not is_elected_leader(SWIFT_HA_RES):
+        action_fail('Must run action on leader unit')
+        return
+
     rings_valid = ['account', 'container', 'object', 'all']
     ring = action_get('ring')
     if ring not in rings_valid:

unit_tests/test_actions.py

@@ -330,7 +330,14 @@ class RemoveDevicesTestCase(CharmTestCase):
             actions.actions, ["action_fail",
                               "action_get",
                               "remove_from_ring",
-                              "balance_rings"])
+                              "balance_rings",
+                              "is_elected_leader"])
+        self.is_elected_leader.return_value = True
+
+    def test_not_leader(self):
+        self.is_elected_leader.return_value = False
+        actions.actions.remove_devices([])
+        self.action_fail.assert_called()
 
     def test_ring_valid(self):
         self.action_get.side_effect = ['account', 'd1']
@@ -354,7 +361,14 @@ class SetWeightTestCase(CharmTestCase):
             actions.actions, ["action_fail",
                               "action_get",
                               "set_weight_in_ring",
-                              "balance_rings"])
+                              "balance_rings",
+                              "is_elected_leader"])
+        self.is_elected_leader.return_value = True
+
+    def test_not_leader(self):
+        self.is_elected_leader.return_value = False
+        actions.actions.set_weight([])
+        self.action_fail.assert_called()
 
     def test_ring_valid(self):
         self.action_get.side_effect = ['account', 'd1', '0.0']