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PyBal is a LVS monitor. It monitors HTTP or DNS servers and adapts LVS state based on the results. PyBal was created for use by Wikimedia.

Unit tests are available under pybal/test/. To run the unit tests and get a coverage report:

pip install -r requirements.txt
coverage run --source=pybal setup.py test && coverage report

Since PyBal is a mission-critical software and a bug can bring down the whole infrastructure, we try to minimize the risk by avoiding having to release large changes when we want to bring a bugfix to production. In order to do so, we do the following:

• We adopt semantic versioning 2.0 so we change the major version for API breaking changes, the minor version for adding new functionality, and the patch version for bugfixes.
• All development of non breaking new features should happen against the master branch, with the exception of minor version-specific bugfixes
• Breaking changes (ones that would trigger a major revision change) should first be developed in a separate development branch named X.0-dev. It will be merged back into master once we're ready to move to a new major release. This way we can work on/test the breaking change while not stopping further development of incremental improvements on the current codebase.
• Whenever we're happy with the new functionality in master and we think we're ready to take that to production, we create a branch named as the minor version (e.g. "1.09"). We'll call these the "release branches".
• When we make a bugfix that applies to the code in master as well, we do the CR/merge on the master branch, and then we cherry-pick the change to the release branches currently maintained. If the bugfix is specific to a release branch (because, for example, the code in master has been rewritten/replaced), we just post it against the release branch.
• New versions should always come from release branches.
• When we decide we don't actively maintain a minor version, a commit to the release branch should be done indicating that.

So let's review how a typical bugfix workflow works:

• The patch to fix the bug is developed and reviewed on master.
• Once it's merged on master, the patch is cherry-picked to the release branches and either merged (if the cherry-pick is clean) or re-reviewed: please apply common sense
• When we're happy with the patch, we create the debian/changelog entry on the release branch. This entry will need to be reintegrated back to the debian/changelog on master, most probably manually in a separate commit.

If your commit is instead adding a new functionality, it should definitely go to master. If it's introducing breaking changes, it goes to the X.0-dev branch currently under development.