Add queue-master-locator config option

queue-master-locator is a configuration option supported by
rabbitmq-server since 3.6, it allows to have control of where the
master queue will be created.

Change-Id: I38cc019b73d062572e19bd532b6bccdaf88638ba
Func-Test-PR: openstack-charmers/zaza-openstack-tests#382
Closes-Bug: #1890759
Signed-off-by: Nicolas Bock <nicolas.bock@canonical.com>

config.yaml

@@ -306,3 +306,12 @@ options:
       When using nrpe to monitor the Rabbitmq host, we monitor functionality on
       one vhost.  This option configures additional vhost name(s) to check.
       Space separated list.
+  queue-master-locator:
+    type: string
+    default: min-masters
+    description: |
+      Queue master location strategy. Available strategies are:
+         - min-masters, Pick the node hosting the minimum number of bound masters.
+         - client-local, Pick the node the client that declares the queue is connected to.
+         - random, Pick a random node.
+      This option is only available for RabbitMQ >= 3.6

hooks/rabbitmq_context.py

@@ -22,7 +22,7 @@
 import ssl_utils
 
 from charmhelpers.contrib.ssl.service import ServiceCA
-from charmhelpers.core.host import is_container
+from charmhelpers.core.host import is_container, cmp_pkgrevno
 from charmhelpers.fetch import apt_install
 from charmhelpers.core.hookenv import (
     open_port,
@@ -186,6 +186,9 @@ def __call__(self):
         if config('connection-backlog'):
             ctxt['connection_backlog'] = config('connection-backlog')
 
+        if cmp_pkgrevno('rabbitmq-server', '3.6') >= 0:
+            ctxt['queue_master_locator'] = config('queue-master-locator')
+
         return ctxt
 
 

templates/rabbitmq.config

@@ -31,7 +31,9 @@
 {%- endif %}
     	]},
 {%- endif %}
-
+{%- if queue_master_locator %}
+        {queue_master_locator, <<"{{ queue_master_locator }}">>},
+{%- endif %}
 {%- if cluster_partition_handling %}
         {cluster_partition_handling, {{ cluster_partition_handling }}}
 {%- endif %}

unit_tests/test_rabbitmq_context.py

@@ -84,18 +84,64 @@ class Uid(object):
 
 class TestRabbitMQClusterContext(unittest.TestCase):
 
+    @mock.patch.object(rabbitmq_context, 'cmp_pkgrevno')
     @mock.patch("rabbitmq_context.config")
-    def test_context_ssl_off(self, config):
-        config.return_value = "ignore"
+    def test_context_ssl_off(self, config, mock_cmp_pkgrevno):
+        config_data = {'cluster-partition-handling': 'ignore',
+                       'connection-backlog': 200,
+                       'queue-master-locator': 'client-local'}
+        config.side_effect = config_data.get
+        mock_cmp_pkgrevno.return_value = 0
 
         self.assertEqual(
             rabbitmq_context.RabbitMQClusterContext().__call__(), {
                 'cluster_partition_handling': "ignore",
-                'connection_backlog': "ignore"
+                'connection_backlog': 200,
+                'queue_master_locator': 'client-local',
+            })
+
+        config.assert_has_calls([mock.call("cluster-partition-handling"),
+                                 mock.call("connection-backlog")],
+                                mock.call('queue-master-locator'))
+
+    @mock.patch.object(rabbitmq_context, 'cmp_pkgrevno')
+    @mock.patch("rabbitmq_context.config")
+    def test_queue_master_locator_min_masters(self, config, mock_cmp_pkgrevno):
+        config_data = {'cluster-partition-handling': 'ignore',
+                       'connection-backlog': 200,
+                       'queue-master-locator': 'min-masters'}
+        config.side_effect = config_data.get
+        mock_cmp_pkgrevno.return_value = 0
+
+        self.assertEqual(
+            rabbitmq_context.RabbitMQClusterContext().__call__(), {
+                'cluster_partition_handling': "ignore",
+                'connection_backlog': 200,
+                'queue_master_locator': 'min-masters',
+            })
+
+        config.assert_has_calls([mock.call("cluster-partition-handling"),
+                                 mock.call("connection-backlog")],
+                                mock.call('queue-master-locator'))
+
+    @mock.patch.object(rabbitmq_context, 'cmp_pkgrevno')
+    @mock.patch("rabbitmq_context.config")
+    def test_rabbit_server_3pt6(self, config, mock_cmp_pkgrevno):
+        config_data = {'cluster-partition-handling': 'ignore',
+                       'queue-master-locator': 'min-masters',
+                       'connection-backlog': 200}
+        config.side_effect = config_data.get
+        mock_cmp_pkgrevno.return_value = -1
+
+        self.assertEqual(
+            rabbitmq_context.RabbitMQClusterContext().__call__(), {
+                'cluster_partition_handling': "ignore",
+                'connection_backlog': 200,
             })
 
         config.assert_has_calls([mock.call("cluster-partition-handling"),
                                  mock.call("connection-backlog")])
+        assert mock.call('queue-master-locator') not in config.mock_calls
 
 
 class TestRabbitMQEnvContext(unittest.TestCase):