Expose max_local_block_devices as an explicit charm option

It's useful to force instance creations to fail if ephemeral drives are
requested when cloud admins want users to use persistent volumes always.

Closes-Bug: #1953561
Change-Id: I1c958b4bcf79512c06de6d81fe55c681bb5f38a7

config.yaml

@@ -770,3 +770,12 @@ options:
       Allow resizing to the same host. Setting this option to True will add the
       source host to the destination options for consideration by the
       scheduler when resizing an instance.
+  max-local-block-devices:
+    type: int
+    default:
+    description: |
+      Maximum number of local devices which can be attached to an
+      instance. Possible values are 0: Creating a local disk is not
+      allowed and letting the request fail, Negative number: Allows
+      unlimited number of local devices, Positive number: Allows only
+      these many number of local devices.

hooks/nova_cc_context.py

@@ -449,6 +449,8 @@ class NovaConfigContext(ch_context.WorkerConfigContext):
             'placement-aggregate-required-for-tenants')
         ctxt['enable_isolated_aggregate_filtering'] = hookenv.config(
             'enable-isolated-aggregate-filtering')
+        ctxt['max_local_block_devices'] = hookenv.config(
+            'max-local-block-devices')
         return ctxt
 
 

templates/icehouse/nova.conf

@@ -93,6 +93,10 @@ keystone_ec2_url = {{ keystone_ec2_url }}
 glance_api_servers = {{ glance_api_servers }}
 {% endif -%}
 
+{% if max_local_block_devices is not none -%}
+max_local_block_devices = {{ max_local_block_devices }}
+{% endif -%}
+
 {% if rbd_pool -%}
 rbd_pool = {{ rbd_pool }}
 rbd_user = {{ rbd_user }}

templates/juno/nova.conf

@@ -99,6 +99,10 @@ keystone_ec2_url = {{ keystone_ec2_url }}
 glance_api_servers = {{ glance_api_servers }}
 {% endif -%}
 
+{% if max_local_block_devices is not none -%}
+max_local_block_devices = {{ max_local_block_devices }}
+{% endif -%}
+
 {% if rbd_pool -%}
 rbd_pool = {{ rbd_pool }}
 rbd_user = {{ rbd_user }}

templates/kilo/nova.conf

@@ -99,6 +99,10 @@ memcached_servers = {{ memcached_servers }}
 keystone_ec2_url = {{ keystone_ec2_url }}
 {% endif -%}
 
+{% if max_local_block_devices is not none -%}
+max_local_block_devices = {{ max_local_block_devices }}
+{% endif -%}
+
 {% if rbd_pool -%}
 rbd_pool = {{ rbd_pool }}
 rbd_user = {{ rbd_user }}

templates/liberty/nova.conf

@@ -102,6 +102,10 @@ memcached_servers = {{ memcached_servers }}
 keystone_ec2_url = {{ keystone_ec2_url }}
 {% endif -%}
 
+{% if max_local_block_devices is not none -%}
+max_local_block_devices = {{ max_local_block_devices }}
+{% endif -%}
+
 {% if rbd_pool -%}
 rbd_pool = {{ rbd_pool }}
 rbd_user = {{ rbd_user }}

templates/mitaka/nova.conf

@@ -87,6 +87,10 @@ quota_server_group_members = {{ quota_server_group_members }}
 
 {% include "parts/novnc" %}
 
+{% if max_local_block_devices is not none -%}
+max_local_block_devices = {{ max_local_block_devices }}
+{% endif -%}
+
 {% if rbd_pool -%}
 rbd_pool = {{ rbd_pool }}
 rbd_user = {{ rbd_user }}

templates/newton/nova.conf

@@ -90,6 +90,10 @@ quota_server_group_members = {{ quota_server_group_members }}
 
 {% include "parts/novnc" %}
 
+{% if max_local_block_devices is not none -%}
+max_local_block_devices = {{ max_local_block_devices }}
+{% endif -%}
+
 {% if rbd_pool -%}
 rbd_pool = {{ rbd_pool }}
 rbd_user = {{ rbd_user }}

templates/ocata/nova.conf

@@ -47,6 +47,10 @@ my_ip = {{ host_ip }}
 
 {% include "parts/novnc" %}
 
+{% if max_local_block_devices is not none -%}
+max_local_block_devices = {{ max_local_block_devices }}
+{% endif -%}
+
 {% if rbd_pool -%}
 rbd_pool = {{ rbd_pool }}
 rbd_user = {{ rbd_user }}

templates/pike/nova.conf

@@ -52,6 +52,10 @@ my_ip = {{ host_ip }}
 
 {% include "parts/novnc" %}
 
+{% if max_local_block_devices is not none -%}
+max_local_block_devices = {{ max_local_block_devices }}
+{% endif -%}
+
 {% if rbd_pool -%}
 rbd_pool = {{ rbd_pool }}
 rbd_user = {{ rbd_user }}

templates/rocky/nova.conf

@@ -52,6 +52,10 @@ my_ip = {{ host_ip }}
 
 {% include "parts/novnc" %}
 
+{% if max_local_block_devices is not none -%}
+max_local_block_devices = {{ max_local_block_devices }}
+{% endif -%}
+
 {% if rbd_pool -%}
 rbd_pool = {{ rbd_pool }}
 rbd_user = {{ rbd_user }}

templates/train/nova.conf

@@ -52,6 +52,10 @@ my_ip = {{ host_ip }}
 
 {% include "parts/novnc" %}
 
+{% if max_local_block_devices is not none -%}
+max_local_block_devices = {{ max_local_block_devices }}
+{% endif -%}
+
 {% if rbd_pool -%}
 rbd_pool = {{ rbd_pool }}
 rbd_user = {{ rbd_user }}

unit_tests/test_nova_cc_contexts.py

@@ -401,6 +401,8 @@ class NovaComputeContextTests(CharmTestCase):
         )
         self.assertEqual(ctxt['enable_isolated_aggregate_filtering'],
                          self.config('enable-isolated-aggregate-filtering'))
+        self.assertEqual(ctxt['max_local_block_devices'],
+                         self.config('max-local-block-devices'))
 
     _pci_alias1 = {
         "name": "IntelNIC",