Neutron API中大多的resource都需要quota limits。
Neutron API暴露出一个extension 来管理quota，Quota limits are enforced at the API layer，
Plugin and ML2 drivers唯一例外是subnet_allocation[1] extension。
不支持per user and 多租户嵌套。
High Level View
主要组件：
- The Quota API extension;
- The Quota Engine.
quota driver：
- neutron.db.quota.driver.DbQuotaDriver
- neutron.quota.ConfDriver
The latter driver is however deprecated.
Quota Management
和其他Neutron extensions不同，它 有自己的own controller class [3].
其中_update_attributes只被调用一次，它会动态的更新Neutron’s resource attribute map [4]
driver operations包括：
- delete_tenant_quota, which simply removes all entries from the ‘quotas’ table for a given tenant identifier;
- update_quota_limit, which adds or updates an entry in the ‘quotas’ tenant for a given tenant identifier and a given resource name;
- _get_quotas, which fetches limits for a set of resource and a given tenant identifier
- _get_all_quotas, which behaves like _get_quotas, but for all tenants.
Resource Usage Info
- CountableResource
- TrackedResource
Quota Enforcement
- 通过count方法得到当前资源的usages.
- 通过 _get_tenant_quotas 得到租户的quota.
- usages减去expired reservations .
- 计算可用资源，与请求资源对比.
Setting up Resource Tracking for a Plugin
@resource_registry.tracked_resources(network=models_v2.Network,
port=models_v2.Port, subnet=models_v2.Subnet, subnetpool=models_v2.SubnetPool)
| [1] | Subnet allocation extension:http://git.openstack.org/cgit/openstack/neutron/tree/neutron/extensions/subnetallocation.py |
| [2] | DB Quota driver class:http://git.openstack.org/cgit/openstack/neutron/tree/neutron/db/quota_db.py#n33 |
| [3] | Quota API extension controller:http://git.openstack.org/cgit/openstack/neutron/tree/neutron/extensions/quotasv2.py#n40 |
| [4] | Neutron resource attribute map:http://git.openstack.org/cgit/openstack/neutron/tree/neutron/api/v2/attributes.py#n639 |
| [5] | Base controller class:http://git.openstack.org/cgit/openstack/neutron/tree/neutron/api/v2/base.py#n50 |
| [6] | http://lists.openstack.org/pipermail/openstack-dev/2015-February/057534.html |