Wrap the Python NeutronClient

Wrap the Python NeutronClient

https://blueprints.launchpad.net/nova/+spec/nova-neutron-refactor

The Neutron client module used by the Neutron implementation of the Openstack Network API is a basic, thin wrapper around the Neutron API. Direct use of the module’s functionality has resulted in pervasive adaptive code throughout the API adapter implementation. The repetitive and occasionally opaque nature of this code makes the implementation difficult to debug and maintain. Providing higher level, Nova oriented abstractions by wrapping the existing client:

  • Makes it easier to implement readable implementations of the networking API implementation.

  • Allows knowledge of the functioning of the Neutron API to be captured in code for reuse by all developers, independent of their Neutron API expertise. This is maintainable, extensible and testable in itself.

  • Provides a natural boundary to hide neutron specific details such as:

    • thrown exceptions

    • JSON request and response translation

Problem description

Direct use of the neutronclient module is pervasive throughout the implementation of the Neutron Network API adapter. This has the following consequences:

  • Construction of JSON requests and parsing of replies is repeated throughout the code.

  • Neutron specific exceptions are allowed to permeate the API boundary to the caller.

  • How well the Neutron client is used varies depending on the expertise of the respective authors. There is no mechanism for capturing best practices that is immediately available to developers.

  • Changes to the Neutron client can require pervasive changes to the adapter implementation.

  • Certain API features are only accessible through contexts with administrative credentials, requiring maintainers to understand which operations are constrained or otherwise affected by administrative credentials.

Use Cases

  • Nova developers should not need to have direct knowledge of Neutron client or API specific details to perform rudimentary code changes.

  • Developers with Neutron expertise need a mechanism to capture best practices in an accessible and immediately useful way for themselves and other developers.

  • Special handling of remote call behavior can be introduced in a manageable and consistent fashion.

Project Priority

This refactoring addresses an issue of significant technical debt and is a step towards deprecating nova-network.

Proposed change

Provide higher level abstractions of the Neutron client calls used by Nova through a class (or family of classes if required). The classes hide construction of JSON requests, translation of replies to Nova objects and Neutron exceptions to Nova exceptions.

Alternatives

Continue to directly use the Neutron client “in-place”, possibly mitigating code repetition through helper methods and performing ad-hoc exception translation through alternate means such as decorators.

Data model impact

None

REST API impact

None

Security impact

None.

Notifications impact

None

Other end user impact

None

Performance Impact

None

Other deployer impact

None

Developer impact

The results of this effort are to be consumed in the refactoring of the adapter so only has impact to developers working on this effort.

Implementation

Assignee(s)

Primary assignee: Brent Eagles (beagles@redhat.com)

One or more sponsors from the core teams should have direct involvement in an, at minimum, advisory capacity. Particularly:

  • Dan Smith for Nova objects

  • Matt Riedemann

  • Maru Newby (Neutron)

Primary assignee: * Brent Eagles beagles@redhat.com

Work Items

  1. Create a class that provides higher level methods for neutron client.

  2. Create tempest tests to exercise wrapper.

Dependencies

None

Testing

The changes will be exercised through the existing CI.

Documentation Impact

None

References

Creative Commons Attribution 3.0 License

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nova-specs