Receive polling-batch-size config

Samples collected can be batched together,
consequently increasing or reducing the
amount of API calls and body data
sent to the configured publisher.

This config is available since Rocky,
receiving the value from ceilometer-charm
to allow its tuning.

Change-Id: I986073fdacd750cf96d662abf1d58844479c25ba
Closes-bug: #1885190

hooks/ceilometer_contexts.py

@@ -49,6 +49,7 @@ class CeilometerServiceContext(OSContextGenerator):
         'service_port',
         'signing_dir',
         'api_version',
+        'polling_batch_size',
     ]
 
     optional_keys = [

templates/rocky/ceilometer.conf

@@ -0,0 +1,49 @@
+# rocky
+###############################################################################
+# [ WARNING ]
+# ceilometer configuration file maintained by Juju
+# local changes may be overwritten.
+###############################################################################
+[DEFAULT]
+debug = {{ debug }}
+verbose = {{ verbose }}
+logdir = /var/log/ceilometer
+
+{% if transport_url -%}
+transport_url = {{ transport_url }}
+{%- endif %}
+
+{% if service_host -%}
+[service_credentials]
+{% if use_internal_endpoints -%}
+auth_url = {{ auth_protocol }}://{{ auth_host }}:{{ auth_port }}
+interface = internalURL
+{% else -%}
+auth_url = {{ service_protocol }}://{{ service_host }}:{{ service_port }}
+{% endif -%}
+project_name = {{ admin_tenant_name }}
+username = {{ admin_user }}
+password = {{ admin_password }}
+{% if api_version == "3" -%}
+project_domain_name = {{ admin_domain_name }}
+user_domain_name = {{ admin_domain_name }}
+{% else -%}
+project_domain_name = default
+user_domain_name = default
+{% endif -%}
+auth_type = password
+{% endif -%}
+
+[polling]
+{% if polling_batch_size -%}
+batch_size = {{ polling_batch_size }}
+{% endif -%}
+
+{% if metering_secret -%}
+[publisher]
+telemetry_secret = {{ metering_secret }}
+{% endif -%}
+
+{% include "section-keystone-authtoken-mitaka" %}
+
+{% include "section-oslo-messaging-rabbit-ocata" %}

unit_tests/test_ceilometer_contexts.py

@@ -56,7 +56,8 @@ class CeilometerContextsTest(CharmTestCase):
             'admin_tenant_name': 'admin',
             'admin_user': 'admin',
             'admin_password': 'password',
-            'metering_secret': 'secret'
+            'metering_secret': 'secret',
+            'polling_batch_size': 50,
         }
         self.test_relation.set(data)
         self.assertEqual(contexts.CeilometerServiceContext()(), data)