Merge ~jamesbeedy/interface-grafana-source:relation_base_to_endpoint into interface-grafana-source:master

[james beedy]

Closes https://bugs.launchpad.net/interface-grafana-source/+bug/1899655

Convert the problematic RelationBase requires endpoint to use reactive.Endpoint.

[Drew Freiberger (afreiberger)]

There is a bug with the related update to charm-grafana. Setting this to WIP awaiting review and remediation of the issue in:
https://code.launchpad.net/%7Ejamesbeedy/charm-grafana/+git/charm-grafana/+merge/393218/+index?ss=1

Unmerged commits

ec02d32... by james beedy on 2020-11-03

only get data from the first unit

3954796... by james beedy on 2020-11-02

RelationBase -> Endpoint

diff --git a/requires.py b/requires.py
index 862f46b..390e1bb 100644
--- a/requires.py
+++ b/requires.py
@@ -1,28 +1,30 @@
-from charms.reactive import hook
-from charms.reactive import RelationBase
-from charms.reactive import scopes
+#!/usr/bin/python3
+from charms.reactive import (
+    Endpoint,
+    clear_flag,
+    set_flag,
+    when_any,
+)
 
 
-class GrafanaRequires(RelationBase):
-    scope = scopes.SERVICE
+class GrafanaRequires(Endpoint):
+    """GrafanaRequires."""
 
-    @hook('{requires:grafana-source}-relation-{joined,changed}')
+    @when_any('endpoint.{endpoint_name}.joined',
+              'endpoint.{endpoint_name}.changed')
     def changed(self):
-        conv = self.conversation()
-        if conv.get_remote('type'):
-            conv.set_state('{relation_name}.available')
+        if self.all_joined_units.received.get('type'):
+            set_flag(f'{self.endpoint_name}.available')
 
-    @hook('{requires:grafana-source}-relation-departed')
-    def broken(self):
-        conv = self.conversation()
-        conv.remove_state('{relation_name}.available')
+    @when_any('endpoint.{endpoint_name}.broken',
+              'endpoint.{endpoint_name}.departed')
+    def departed(self):
+        clear_flag(f'{self.endpoint_name}.available')
 
     def datasources(self):
         """
         Returns a list of available datasources
-
         The return value is a list of dicts of the following form::
-
             [
                 {
                     'service_name': remote_service_name,
@@ -37,17 +39,29 @@ class GrafanaRequires(RelationBase):
             ]
         """
         datasources = []
-        for conv in self.conversations():
-            ds = {'service_name': conv.scope.split('/')[0],
-                  'type': conv.get_remote('type'),
-                  'url': conv.get_remote('url'),
-                  'description': conv.get_remote('description')
-                  }
-            if conv.get_remote('username') and conv.get_remote('password'):
-                ds['username'] = conv.get_remote('username')
-                ds['password'] = conv.get_remote('password')
-            if conv.get_remote('database'):
-                ds['database'] = conv.get_remote('database')
+
+        for relation in self.relations:
+
+            # Only look at a single unit
+            unit = relation.joined_units[0]
+
+            ds = {
+                'service_name': relation.application_name,
+                'type': unit.received.get('type'),
+                'url': unit.received.get('url'),
+                'description': unit.received.get('description'),
+            }
+
+            username = unit.received.get('username')
+            password = unit.received.get('password')
+            if username and password:
+                ds['username'] = username
+                ds['password'] = password
+
+            database = unit.received.get('database')
+            if database:
+                ds['database'] = database
+
             datasources.append(ds)
 
         return datasources