Development Guidelines

Coding Guidelines

For the most part we try to follow PEP 8 guidelines which can be viewed here: http://www.python.org/dev/peps/pep-0008/

There is a useful pep8 command line tool for checking files for pep8 compliance which can be installed with easy_install pep8.

Testing Guidelines

Swift has a comprehensive suite of tests that are run on all submitted code, and it is recommended that developers execute the tests themselves to catch regressions early. Developers are also expected to keep the test suite up-to-date with any submitted code changes.

Swift’s suite of unit tests can be executed in an isolated environment with Tox: http://tox.testrun.org/

To execute the unit tests:

  • Install Tox:

    • pip install tox

  • If you do not have python 2.6 installed (as in 12.04):

    • Add export TOXENV=py27,pep8 to your ~/.bashrc
    • . ~/.bashrc

  • Run Tox from the root of the swift repo:

    • tox

    Remarks: If you installed using: cd ~/swift; sudo python setup.py develop, you may need to do: cd ~/swift; sudo chown -R ${USER}:${USER} swift.egg-info prior to running tox.

  • Optionally, run only specific tox builds:

    • tox -e pep8,py27

Note

As of tox version 2.0.0, most environment variables are not automatically passed to the test environment. Swift’s tox.ini overrides this default behavior so that variable names matching SWIFT_* and *_proxy will be passed, but you may need to run tox –recreate for this to take effect after upgrading from tox<2.0.0.

Conversely, if you do not want those environment variables to be passed to the test environment then you will need to unset them before calling tox.

Also, if you ever encounter DistributionNotFound, try to use tox –recreate or remove the .tox directory to force tox to recreate the dependency list.

The functional tests may be executed against a SAIO - Swift All In One or other running Swift cluster using the command:

  • tox -e func

The endpoint and authorization credentials to be used by functional tests should be configured in the test.conf file as described in the section Setting up scripts for running Swift.

The environment variable SWIFT_TEST_POLICY may be set to specify a particular storage policy name that will be used for testing. When set, tests that would otherwise not specify a policy or choose a random policy from those available will instead use the policy specified. Tests that use more than one policy will include the specified policy in the set of policies used. The specified policy must be available on the cluster under test.

For example, this command would run the functional tests using policy ‘silver’:

SWIFT_TEST_POLICY=silver tox -e func

If the test.conf file is not found then the functional test framework will instantiate a set of Swift servers in the same process that executes the functional tests. This ‘in-process test’ mode may also be enabled (or disabled) by setting the environment variable SWIFT_TEST_IN_PROCESS to a true (or false) value prior to executing tox -e func.

When using the ‘in-process test’ mode, the optional in-memory object server may be selected by setting the environment variable SWIFT_TEST_IN_MEMORY_OBJ to a true value.

The ‘in-process test’ mode searches for proxy-server.conf and swift.conf config files from which it copies config options and overrides some options to suit in process testing. The search will first look for config files in a <custom_conf_source_dir> that may optionally be specified using the environment variable:

SWIFT_TEST_IN_PROCESS_CONF_DIR=<custom_conf_source_dir>

If SWIFT_TEST_IN_PROCESS_CONF_DIR is not set, or if a config file is not found in <custom_conf_source_dir>, the search will then look in the etc/ directory in the source tree. If the config file is still not found, the corresponding sample config file from etc/ is used (e.g. proxy-server.conf-sample or swift.conf-sample).

When using the ‘in-process test’ mode SWIFT_TEST_POLICY may be set to specify a particular storage policy name that will be used for testing as described above. When set, this policy must exist in the swift.conf file and its corresponding ring file must exist in <custom_conf_source_dir> (if specified) or etc/. The test setup will set the specified policy to be the default and use its ring file properties for constructing the test object ring. This allows in-process testing to be run against various policy types and ring files.

For example, this command would run the in-process mode functional tests using config files found in $HOME/my_tests and policy ‘silver’:

SWIFT_TEST_IN_PROCESS=1 SWIFT_TEST_IN_PROCESS_CONF_DIR=$HOME/my_tests \
   SWIFT_TEST_POLICY=silver tox -e func

Coding Style

Swift use flake8 with the OpenStack hacking module to enforce coding style.

Install flake8 and hacking with pip or by the packages of your Operating System.

It is advised to integrate flake8+hacking with your editor to get it automated and not get caught by Jenkins.

For example for Vim the syntastic plugin can do this for you.

Documentation Guidelines

The documentation in docstrings should follow the PEP 257 conventions (as mentioned in the PEP 8 guidelines).

More specifically:

  1. Triple quotes should be used for all docstrings.
  2. If the docstring is simple and fits on one line, then just use one line.
  3. For docstrings that take multiple lines, there should be a newline after the opening quotes, and before the closing quotes.
  4. Sphinx is used to build documentation, so use the restructured text markup to designate parameters, return values, etc. Documentation on the sphinx specific markup can be found here: http://sphinx.pocoo.org/markup/index.html
Installing Sphinx:
  1. Install sphinx (On Ubuntu: sudo apt-get install python-sphinx)
  2. python setup.py build_sphinx