Development Guidelines

Coding Guidelines

For all the Python code in Sahara we have a rule - it should pass PEP 8. All Bash code should pass bashate.

To check your code against PEP 8 and bashate run:

$ tox -e pep8


For more details on coding guidelines see file HACKING.rst in the root of Sahara repo.

Static analysis

The static analysis checks are optional in Sahara. but they are still very useful. The gate job will inform you if the number of static analysis warnings has increased after your change. We recommend to always check the static warnings.

To run the check commit yor change first and execute the following command:

$ tox -e pylint

Modification of Upstream Files

We never modify upstream files in Sahara. Any changes in upstream files should be made in the upstream project and then merged back in to Sahara. This includes whitespace changes, comments, and typos. Any change requests containing upstream file modifications are almost certain to receive lots of negative reviews. Be warned.

Examples of upstream files are default xml configuration files used to configure Hadoop, or code imported from the OpenStack Oslo project. The xml files will usually be found in resource directories with an accompanying README file that identifies where the files came from. For example:

$ pwd

$ ls
core-default.xml     hdfs-default.xml    oozie-default.xml   README.rst
create_oozie_db.sql  mapred-default.xml  post_conf.template  yarn-default.xml

Testing Guidelines

Sahara has a 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.

Unit tests are located at sahara/tests/unit.

Sahara’s suite of unit tests can be executed in an isolated environment with Tox. To execute the unit tests run the following from the root of Sahara repo:

$ tox -e py27

Documentation Guidelines

All Sahara docs are written using Sphinx / RST and located in the main repo in doc directory. You can add/edit pages here to update site.

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:

Run the following command to build docs locally.

$ tox -e docs

After it you can access generated docs in doc/build/ directory, for example, main page - doc/build/html/index.html.

To make docs generation process faster you can use:

$ SPHINX_DEBUG=1 tox -e docs

or to avoid sahara reinstallation to virtual env each time you want to rebuild docs you can use the following command (it could be executed only after running tox -e docs first time):

$ SPHINX_DEBUG=1 .tox/docs/bin/python build_sphinx


For more details on documentation guidelines see file HACKING.rst in the root of Sahara repo.

Event log Guidelines

Currently Sahara keep with cluster useful information about provisioning. Cluster provisioning can be represented as a linear series of provisioning steps, which are executed one after another. Also each step would consist of several events. The amount of events depends on the step and the amount of instances in the cluster. Also each event can contain information about cluster, instance, and node group. In case of errors, this event would contain information about reasons of errors. Each exception in sahara contains a unique identifier that will allow the user to find extra information about the reasons for errors in the sahara logs. Here you can see an example of provisioning progress information.

This means that if you add some important phase for cluster provisioning to sahara code, it’s recommended to add new provisioning step for this phase. It would allow users to use event log for handling errors during this phase.

Sahara already have special utils for operating provisioning steps and events in module sahara/utils/


It’s strictly recommended not use conductor event log ops directly to assign events and operate provisioning steps.


You should not add a new provisioning step until the previous step successfully completed.


It’s strictly recommended to use event_wrapper for events handling

OpenStack client usage guidelines

The sahara project uses several OpenStack clients internally. These clients are all wrapped by utility functions which make using them more convenient. When developing sahara, if you need to use a OpenStack client you should check the sahara.utils.openstack package for the appropriate one.

When developing new OpenStack client interactions in sahara, it is important to understand the sahara.service.sessions package and the usage of keystone Session and auth plugin objects(for example, Token or Password). Sahara is migrating all clients to use this authentication methodology, where available. For more information on using sessions with keystone, please see