Support Nova microversions for Nova plugin

This feature adds the support for Nova APIs with microversions. This would support Searchlight providing the fields that are added in new microversions of Nova APIs.

Problem Description

Nova have deprecated v2.0 API and starting to remove the codes from tree. Nova v2.1 API is designed with the microversion mechanism, that is, when new data fields are added to one particular resource, the backward compatibility is ensured by adding new microversions to related APIs 1.

For example, in 2, a new field description is added for servers, it is used for users to make a simple string to describe their servers, it would be very useful if we can also provide this field.

The changes that were made for each microversions could be found in 3.

Proposed Change

Currently, when we initialize nova client, it is hard coded to use version=2, this is bad in two ways:

1. The v2.0 nova API is deprecated and the code will be removed in Newton 4.

  1. It can not support microversions if it is hard coded.

In this BP, a new configure option compute_api_version will be added in the configuration file. When we initialize nova client, this config option will be used as the version of the API version. The default value of this config option will be set to 2.1 in the design of this BP and can be modified in the future according to the changes in Nova API.

The supported data fields will be also updated according to the provided microversion.


Hard code the version to 2.1 as 2.0 will no longer be usable soon. But the newly added data fields cannot be supported.