Refactoring for fuelclient

https://blueprints.launchpad.net/fuel/+spec/refactoring-for-fuelclient

We need to perform refactoring for fuelclient for improving reusability for its code base and gain more control for both whole system and particular parts of it.

Problem description

Now there are several issues in architecture of the project which cause difficulties in maintaining, implementing new logic and reusing existing code. These parts are:

• APIclient code for maintaining http communication with nailgun server; now slightly obsolete python module urllib2 is using so code for request operations is pretty excessive
• Formatter for console output; own written invention so it is hard to dive into, also not flexible for future changes
• Objects hierarchy; is overwhelming with many interconnections between objects, may be simplified
• Tests coverage; now only limited set of tests that check simple use cases is present, so it must be extended and if possible whole testing system should be rewritten to meet OS best practices in cli testing.

Proposed change

There are several proposes for every problem mentioned in previous section:

• substitute urllib2 with requests module, this will leads to more simplified code in APIclient
• include cliff framework for cli and formatter part of the system
• perform minor refactoring when it needed.

Alternatives

All other basic tools such argparse or docopt doesn’t suffice in case of fuelclient because we need to implement our own object hierarchy instead of using base classes of framework which leads to complicated structure as that we have now. There also others framework for building cli application (e.g. http://click.pocoo.org/) but chosen tools are wide using in OS community and are best practices for building OS related application.

Data model impact

None

REST API impact

None

Upgrade impact

Refactoring requires some additional packages to be installed on master node so they should be present after upgrade to version which includes change upon the table.

Security impact

None

Notifications impact

None

Other end user impact

End users workflow may be affected as interface of system will be changed so adequate documentation must be provided for them

Performance Impact

None

Other deployer impact

One should add needed rpm’s to fuelclient spec. Packages must be already present in repos.

Developer impact

After refactoring particular parts of the system may be reused in other projects when such functionality is needed as ostf, system tests etc. Also using cliff simplifying addition of new cli actions trough mechanism of entry points for package.

Implementation

Assignee(s)

Primary assignee:

aroma-x

Work Items

Whole task may be divide into following separate changes:

• plugging requests
• plugging cliff

Dependencies

Refactoring relies on additional package - python-cliff

Testing

As purpose of the refactoring is to bring well recommended itself in OS community technologies and tools it is naturally that testing system must be changed too in order to use best practices from corresponding OS development area, i.e. testing of cli clients. Also current coverage of use cases must be extended as it is not enough for such big project as nailgun.

Documentation Impact

Interface of fuelclient may be changed after refactoring so it must be mirrored into corresponding documentation

References

Cliff documentation: http://cliff.readthedocs.org/en/latest/

Requests documentation: http://docs.python-requests.org/en/latest/