Add database pool size/overflow config options

Introduces two new config options, 'db-max-pool-size' and
'db-max-overflow', allowing charms to configure oslo.db
connection pool behaviour when rendering database connection settings.

Closes-Bug: #2132315
Change-Id: I5c4088b631c5a5b6ed99b621b0ee245576307e0f
Signed-off-by: Raven Kaur <raven.kaur@canonical.com>

config.yaml

@@ -112,6 +112,19 @@ options:
     type: string
     default: neutron
     description: Database name for Neutron (if enabled).
+  db-max-pool-size:
+    type: int
+    default:
+    description: |
+      Optional override for the maximum number of SQL connections to keep
+      open in a pool. Leave unset to use the service default. Setting a
+      value of 0 indicates no limit.
+  db-max-overflow:
+    type: int
+    default:
+    description: |
+      Optional override for the maximum number of connections to allow for
+      connection pool overflow. Leave unset to use the service default.
   region:
     type: string
     default: RegionOne

hooks/neutron_api_utils.py

@@ -188,6 +188,7 @@ BASE_RESOURCE_MAP = OrderedDict([
                      context.WorkerConfigContext(),
                      context.InternalEndpointContext(),
                      context.MemcacheContext(),
+                     context.OsloDBContext(),
                      neutron_api_context.DesignateContext(),
                      neutron_api_context.NeutronInfobloxContext(),
                      context.KeystoneAuditMiddleware(service=SERVICE)],

templates/parts/section-database

@@ -1,4 +1,10 @@
 {% if database_host -%}
 [database]
 connection = {{ database_type }}://{{ database_user }}:{{ database_password }}@{{ database_host }}/{{ database }}{% if database_ssl_ca %}?ssl_ca={{ database_ssl_ca }}{% if database_ssl_cert %}&ssl_cert={{ database_ssl_cert }}&ssl_key={{ database_ssl_key }}{% endif %}{% endif %}
+{% if db_max_pool_size is number %}
+max_pool_size = {{ db_max_pool_size }}
+{% endif %}
+{% if db_max_overflow is number %}
+max_overflow = {{ db_max_overflow }}
+{% endif %}
 {% endif -%}