Fix for multiple status-set - related to bug 1588462

This change fixes the obvious race for a status_set() between
check_optional_interfaces() and assess_status() as the later calls the former
which calls status_set(), returns the status, which is then potentially set
again by the assess_status() function.  This cleans up the code so that only a
single status_set() is performed when calling assess_status().

Change-Id: I05e071d635819c516ab76684842a25a9c2f81d83
Related-Bug:#1588462

hooks/neutron_utils.py

@@ -24,7 +24,6 @@ from charmhelpers.core.hookenv import (
     unit_private_ip,
     is_relation_made,
     relation_ids,
-    status_get,
 )
 from charmhelpers.core.templating import render
 from charmhelpers.fetch import (
@@ -48,7 +47,6 @@ from charmhelpers.contrib.openstack.utils import (
     git_src_dir,
     git_pip_venv_dir,
     get_hostname,
-    set_os_workload_status,
     make_assess_status_func,
     pause_unit,
     resume_unit,
@@ -1202,10 +1200,29 @@ def git_post_install(projects_yaml):
            neutron_vpn_agent_context, perms=0o644)
 
 
-def check_optional_relations(configs):
-    required_interfaces = {}
+def get_optional_interfaces():
+    """Return the optional interfaces that should be checked if the relavent
+    relations have appeared.
+    :returns: {general_interface: [specific_int1, specific_int2, ...], ...}
+    """
+    optional_interfaces = {}
+    if relation_ids('ha'):
+        optional_interfaces['ha'] = ['cluster']
+    return optional_interfaces
+
+
+def check_optional_relations(configs):
+    """Check that if we have a relation_id for high availability that we can
+    get the hacluster config.  If we can't then we are blocked.
+
+    This function is called from assess_status/set_os_workload_status as the
+    charm_func and needs to return either "unknown", "" if there is no problem
+    or the status, message if there is a problem.
+
+    :param configs: an OSConfigRender() instance.
+    :return 2-tuple: (string, string) = (status, message)
+    """
     if relation_ids('ha'):
-        required_interfaces['ha'] = ['cluster']
         try:
             get_hacluster_config()
         except:
@@ -1213,11 +1230,9 @@ def check_optional_relations(configs):
                     'hacluster missing configuration: '
                     'vip, vip_iface, vip_cidr')
 
-    if required_interfaces:
-        set_os_workload_status(configs, required_interfaces)
-        return status_get()
-    else:
-        return 'unknown', 'No optional relations'
+    # return 'unknown' as the lowest priority to not clobber an existing
+    # status.
+    return 'unknown', ''
 
 
 def assess_status(configs):
@@ -1241,15 +1256,21 @@ def assess_status_func(configs):
     Used directly by assess_status() and also for pausing and resuming
     the unit.
 
+    NOTE: REQUIRED_INTERFACES is augmented with the optional interfaces
+    depending on the current config before being passed to the
+    make_assess_status_func() function.
+
     NOTE(ajkavanagh) ports are not checked due to race hazards with services
     that don't behave sychronously w.r.t their service scripts.  e.g.
     apache2.
     @param configs: a templating.OSConfigRenderer() object
     @return f() -> None : a function that assesses the unit's workload status
     """
+    required_interfaces = REQUIRED_INTERFACES.copy()
+    required_interfaces.update(get_optional_interfaces())
     active_services = [s for s in services() if s not in STOPPED_SERVICES]
     return make_assess_status_func(
-        configs, REQUIRED_INTERFACES,
+        configs, required_interfaces,
         charm_func=check_optional_relations,
         services=active_services, ports=None)
 

unit_tests/test_neutron_utils.py

@@ -1177,6 +1177,7 @@ class TestNeutronAgentReallocation(CharmTestCase):
             asf.assert_called_once_with('test-config')
             callee.assert_called_once_with()
 
+    @patch.object(neutron_utils, 'get_optional_interfaces')
     @patch.object(neutron_utils, 'check_optional_relations')
     @patch.object(neutron_utils, 'REQUIRED_INTERFACES')
     @patch.object(neutron_utils, 'services')
@@ -1185,12 +1186,16 @@ class TestNeutronAgentReallocation(CharmTestCase):
                                 make_assess_status_func,
                                 services,
                                 REQUIRED_INTERFACES,
-                                check_optional_relations):
+                                check_optional_relations,
+                                get_optional_interfaces):
         services.return_value = ['s1']
+        REQUIRED_INTERFACES.copy.return_value = {'int': ['test 1']}
+        get_optional_interfaces.return_value = {'opt': ['test 2']}
         neutron_utils.assess_status_func('test-config')
         # ports=None whilst port checks are disabled.
         make_assess_status_func.assert_called_once_with(
-            'test-config', REQUIRED_INTERFACES,
+            'test-config',
+            {'int': ['test 1'], 'opt': ['test 2']},
             charm_func=check_optional_relations, services=['s1'], ports=None)
 
     def test_pause_unit_helper(self):