1. Frequently Asked Questions

Q:Who is this document intended for?
A:Anyone who wishes to read and/or edit the Pacemaker source code. Casual contributors should feel free to read just this FAQ, and consult other chapters as needed.

Q:Where is the source code for Pacemaker?
A:The source code for Pacemaker is kept on GitHub, as are all software projects under the ClusterLabs umbrella. Pacemaker uses Git for source code management. If you are a Git newbie, the gittutorial(7) man page is an excellent starting point. If you’re familiar with using Git from the command line, you can create a local copy of the Pacemaker source code with: git clone https://github.com/ClusterLabs/pacemaker.git


What are the different Git branches and repositories used for?

  • The main branch is the primary branch used for development.
  • The 2.1 branch is the current release branch. Normally, it does not receive any changes, but during the release cycle for a new release, it will contain release candidates. During the release cycle, certain bug fixes will go to the 2.1 branch first (and be pulled into main later).
  • The 2.0 branch, 1.1 branch, and separate 1.0 repository are frozen snapshots of earlier release series, no longer being developed.
  • Messages will be posted to the developers@ClusterLabs.org mailing list during the release cycle, with instructions about which branches to use when submitting requests.

Q:How do I build from the source code?
A:See INSTALL.md in the main checkout directory.

Q:What coding style should I follow?
A:You’ll be mostly fine if you simply follow the example of existing code. When unsure, see the relevant chapter of this document for language-specific recommendations. Pacemaker has grown and evolved organically over many years, so you will see much code that doesn’t conform to the current guidelines. We discourage making changes solely to bring code into conformance, as any change requires developer time for review and opens the possibility of adding bugs. However, new code should follow the guidelines, and it is fine to bring lines of older code into conformance when modifying that code for other reasons.


How should I format my Git commit messages?


An example is “Feature: scheduler: wobble the frizzle better”.

  • The first part is the type of change, used to automatically generate the change log for the next release. Commit messages with the following will be included in the change log:

    • Feature for new features
    • Fix for bug fixes (Bug or High also work)
    • API for changes to the public API

    Everything else will not automatically be in the change log, and so don’t really matter, but types commonly used include:

    • Log for changes to log messages or handling
    • Doc for changes to documentation or comments
    • Test for changes in CTS and regression tests
    • Low, Med, or Mid for bug fixes not significant enough for a change log entry
    • Refactor for refactoring-only code changes
    • Build for build process changes
  • The next part is the name of the component(s) being changed, for example, controller or libcrmcommon (it’s more free-form, so don’t sweat getting it exact).

  • The rest briefly describes the change. The git project recommends the entire summary line stay under 50 characters, but more is fine if needed for clarity.

  • Except for the most simple and obvious of changes, the summary should be followed by a blank line and a longer explanation of why the change was made.

Q:How can I test my changes?
A:The source repository has some unit tests for simple functions, though this is a recent effort without much coverage yet. Pacemaker’s Cluster Test Suite (CTS) has regression tests for most major components; these will automatically be run for any pull requests submitted through GitHub, and are sufficient for most changes. Additionally, CTS has a lab component that can be used to set up a test cluster and run a wide variety of complex tests, for testing major changes. See cts/README.md in the source repository for details.

Q:What is Pacemaker’s license?
A:Except where noted otherwise in the file itself, the source code for all Pacemaker programs is licensed under version 2 or later of the GNU General Public License (GPLv2+), its headers, libraries, and native language translations under version 2.1 or later of the less restrictive GNU Lesser General Public License (LGPLv2.1+), its documentation under version 4.0 or later of the Creative Commons Attribution-ShareAlike International Public License (CC-BY-SA-4.0), and its init scripts under the Revised BSD license. If you find any deviations from this policy, or wish to inquire about alternate licensing arrangements, please e-mail the developers@ClusterLabs.org mailing list. Licensing issues are also discussed on the ClusterLabs wiki.

Q:How can I contribute my changes to the project?
A:Contributions of bug fixes or new features are very much appreciated! Patches can be submitted as pull requests via GitHub (the preferred method, due to its excellent features), or e-mailed to the developers@ClusterLabs.org mailing list as an attachment in a format Git can import. Authors may only submit changes that they have the right to submit under the open source license indicated in the affected files.

Q:What if I still have questions?
A:Ask on the developers@ClusterLabs.org mailing list for development-related questions, or on the users@ClusterLabs.org mailing list for general questions about using Pacemaker. Developers often also hang out on the [ClusterLabs IRC channel](https://wiki.clusterlabs.org/wiki/ClusterLabs_IRC_channel).