Do not set ha.available until clustered

The interface was setting ha.available immediately with no gating.

The hacluster charm sets a relation variable, clustered, when it has
enough peers and has setup corosync. This change updates the
interface to react to this setting. Only set ha.available when
clustered is set and True.

Change-Id: I23eb5e70537a62d5b9e5e24d09f37519b63a1717
Closes-Bug: #1749280

requires.py

@@ -18,6 +18,7 @@ from charms.reactive import hook
 from charms.reactive import RelationBase
 from charms.reactive import scopes
 from charms.reactive.helpers import data_changed
+from charmhelpers.core import hookenv
 
 
 class HAClusterRequires(RelationBase):
@@ -32,13 +33,38 @@ class HAClusterRequires(RelationBase):
 
     @hook('{requires:hacluster}-relation-changed')
     def changed(self):
-        self.set_state('{relation_name}.available')
+        if self.is_clustered():
+            self.set_state('{relation_name}.available')
+        else:
+            self.remove_state('{relation_name}.available')
 
     @hook('{requires:hacluster}-relation-{broken,departed}')
     def departed(self):
         self.remove_state('{relation_name}.available')
         self.remove_state('{relation_name}.connected')
 
+    def is_clustered(self):
+        """Has the hacluster charm set clustered?
+
+        The hacluster charm sets cluster=True when it determines it is ready.
+        Check the relation data for clustered and force a boolean return.
+
+        :returns: boolean
+        """
+        clustered_values = self.get_remote_all('clustered')
+        if clustered_values:
+            # There is only ever one subordinate hacluster unit
+            clustered = clustered_values[0]
+            # Future versions of hacluster will return a bool
+            # Current versions return a string
+            if type(clustered) is bool:
+                return clustered
+            elif (clustered is not None and
+                    (clustered.lower() == 'true' or
+                     clustered.lower() == 'yes')):
+                return True
+        return False
+
     def bind_on(self, iface=None, mcastport=None):
         relation_data = {}
         if iface:
@@ -167,3 +193,16 @@ class HAClusterRequires(RelationBase):
                 resources.group(group, *dns_res_group_members)
 
         self.set_local(resources=resources)
+
+    def get_remote_all(self, key, default=None):
+        """Return a list of all values presented by remote units for key"""
+        values = []
+        for conversation in self.conversations():
+            for relation_id in conversation.relation_ids:
+                for unit in hookenv.related_units(relation_id):
+                    value = hookenv.relation_get(key,
+                                                 unit,
+                                                 relation_id) or default
+                    if value:
+                        values.append(value)
+        return list(set(values))