Add peer relation and handler

advanced_sunbeam_openstack/charm.py

@@ -99,6 +99,12 @@ class OSBaseOperatorCharm(ops.charm.CharmBase):
                 self.default_public_ingress_port,
                 self.configure_charm)
             handlers.append(self.ingress)
+        if self.can_add_handler('peers', handlers):
+            self.peers = sunbeam_rhandlers.BasePeerHandler(
+                self,
+                'peers',
+                self.configure_charm)
+            handlers.append(self.peers)
         return handlers
 
     def get_pebble_handlers(self) -> List[sunbeam_chandlers.PebbleHandler]:
@@ -206,6 +212,14 @@ class OSBaseOperatorCharm(ops.charm.CharmBase):
         """Determine whether the service has been boostrapped."""
         return self._state.bootstrapped
 
+    def leader_set(self, key: str, value: str) -> None:
+        """Set data on the peer relation."""
+        self.peers.set_app_data(key, value)
+
+    def leader_get(self, key: str) -> str:
+        """Retrieeve data from the peer relation."""
+        return self.peers.get_app_data(key)
+
 
 class OSBaseOperatorAPICharm(OSBaseOperatorCharm):
     """Base class for OpenStack API operators"""

advanced_sunbeam_openstack/interfaces.py

@@ -0,0 +1,89 @@
+#!/usr/bin/env python3
+
+import logging
+import typing
+
+from ops.framework import EventBase
+from ops.framework import EventSource
+from ops.framework import Object
+from ops.framework import ObjectEvents
+from ops.framework import StoredState
+
+
+class PeersRelationCreatedEvent(EventBase):
+    """
+    The PeersRelationCreatedEvent indicates that the peer relation now exists.
+    It does not indicate that any peers are available or have joined, simply
+    that the relation exists. This is useful to to indicate that the
+    application databag is available for storing information shared across
+    units.
+    """
+    pass
+
+
+class PeersDataChangedEvent(EventBase):
+    """
+    The CharmPasswordChangedEvent indicates that the leader unit has changed
+    the password that the charm administrator uses.
+    """
+    pass
+
+
+class PeersEvents(ObjectEvents):
+    peers_relation_created = EventSource(PeersRelationCreatedEvent)
+    peers_data_changed = EventSource(PeersDataChangedEvent)
+
+
+class OperatorPeers(Object):
+
+    on = PeersEvents()
+    state = StoredState()
+
+    def __init__(self, charm, relation_name):
+        super().__init__(charm, relation_name)
+        self.relation_name = relation_name
+        self.framework.observe(
+            charm.on[relation_name].relation_created,
+            self.on_created
+        )
+        self.framework.observe(
+            charm.on[relation_name].relation_changed,
+            self.on_changed
+        )
+
+    @property
+    def peers_rel(self):
+        return self.framework.model.get_relation(self.relation_name)
+
+    @property
+    def _app_data_bag(self) -> typing.Dict[str, str]:
+        """
+
+        """
+        return self.peers_rel.data[self.peers_rel.app]
+
+    def on_created(self, event):
+        logging.info('Peers on_created')
+        self.on.peers_relation_created.emit()
+
+    def on_changed(self, event):
+        logging.info('Peers on_changed')
+        self.on.peers_data_changed.emit()
+
+    def set_app_data(self, key, value) -> None:
+        """
+
+        """
+        self._app_data_bag[key] = value
+
+    def get_app_data(self, key) -> None:
+        """
+
+        """
+        return self._app_data_bag.get(key)
+
+    def get_all_app_data(self) -> None:
+        """
+
+        """
+        return self._app_data_bag

advanced_sunbeam_openstack/relation_handlers.py

@@ -27,6 +27,7 @@ import charms.mysql.v1.mysql as mysql
 import charms.sunbeam_rabbitmq_operator.v0.amqp as sunbeam_amqp
 import charms.sunbeam_identity_service_operator.v0.identity_service \
     as sunbeam_id_svc
+import advanced_sunbeam_openstack.interfaces as sunbeam_interfaces
 
 logger = logging.getLogger(__name__)
 
@@ -304,3 +305,37 @@ class IdentityServiceRequiresHandler(RelationHandler):
             return bool(self.interface.service_password)
         except AttributeError:
             return False
+
+
+class BasePeerHandler(RelationHandler):
+
+    def setup_event_handler(self):
+        """Configure event handlers for peer relation."""
+        logger.debug("Setting up peer event handler")
+        peer_int = sunbeam_interfaces.OperatorPeers(
+            self.charm,
+            self.relation_name,
+        )
+        self.framework.observe(
+            peer_int.on.peers_data_changed,
+            self._on_peers_data_changed)
+        return peer_int
+
+    def _on_peers_data_changed(self, event) -> None:
+        self.callback_f(event)
+
+    @property
+    def ready(self) -> bool:
+        return True
+
+    def context(self):
+        try:
+            return self.interface.get_all_app_data()
+        except AttributeError:
+            return {}
+
+    def set_app_data(self, key, value):
+        self.interface.set_app_data(key, value)
+
+    def get_app_data(self, key):
+        self.interface.get_app_data(key)

unit_tests/test_charms.py

@@ -155,6 +155,7 @@ TEMPLATE_CONTENTS = """
 {{ amqp.transport_url }}
 {{ amqp.hostname }}
 {{ identity_service.service_password }}
+{{ peers.foo }}
 """
 
 

unit_tests/test_core.py

@@ -102,8 +102,13 @@ class TestOSBaseOperatorAPICharm(test_utils.CharmTestCase):
         self.harness.container_pebble_ready('my-service')
 
     def test_write_config(self):
+        rel_id = self.harness.add_relation('peers', 'my-service')
+        self.harness.add_relation_unit(
+            rel_id,
+            'my-service/1')
         self.harness.set_leader()
         self.set_pebble_ready()
+        self.harness.charm.leader_set("foo", "bar")
         test_utils.add_api_relations(self.harness)
         expect_entries = [
             '/bin/wsgi_admin',
@@ -111,7 +116,8 @@ class TestOSBaseOperatorAPICharm(test_utils.CharmTestCase):
             'true',
             'rabbit://my-service:rabbit.pass@10.0.0.13:5672/openstack',
             'rabbithost1.local',
-            'svcpass1']
+            'svcpass1',
+            'bar']
         expect_string = '\n' + '\n'.join(expect_entries)
         self.assertEqual(
             self.container_calls['push']['/etc/my-service/my-service.conf'],