Release plan

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Note  As of December 2015, the release plan is in the process of being changed so that the description below will no longer be accurate:
Cquote1.png Hi Everybody,

Today, December 17th would be the day to announce the feature freeze for 3.8 if we were following the usual release schedule.

A while ago I proposed a change in that schedule and I have spent some time on preparing the scripts for an automated release process since then. I think I have pretty much everything ready to go for automated releases and now I'd like to give it a first try for the 3.8 release next year.

For the first execution, I'd like to trigger the scripts manually on my local machine instead of Jenkins to have some better control of it. If it works out as expected, I'll put this onto our Jenkins server afterwards to be executed automatically for the release following after 3.8.

For now, I propose the following and would do so if nobody objects:

  • There is no feature freeze for the next (3.8) and the following releases
  • On Jan., 17th I trigger my first script to create release/3.8 branches with version 3.8.1 (!)
  • Immediately after that I let Jenkins create the binaries for 3.8.1 and we have our first release
  • Patches going into the release/3.8 branch automatically trigger a new build with a previous increase of the micro version number (3.8.2, 3.8.3,..) and we immediately have a bugfix release
  • On 'next', version numbers go to 3.9.0
  • Nightly builds are created from next after every push in that branch

After a to-be-defined period (my proposal: 3 month) we start over:

  • Create a release/3.9 branch with version 3.9.1
  • etc. etc.

Note: there will be no odd-even version number scheme (odd equals unstable, even equals stable). Instead, x.x.0 is unstable, nightly from next and x.x.n where n >= 1 is a stable release.

If everything works as expected, we have a major release every to-be-defined months, a bugfix release after every push to the release branch and a nightly build after every push to 'next'.

I hope this sounds reasonable and keeps everybody happy.

Feedback welcome.

— Torsten Dreyer (Dec 17th, 2015). [Flightgear-devel] Relesae 3.8.
(powered by Instant-Cquotes)
Current release: 2020.1 (11 May 2020)
Next release: 2020.2 (109 days from now)
See release plan for details.

The release plan is the process by which a new version of FlightGear is released. The release plan is actually a continual work-in-progress, and is refined with every new release.

The original release plan.

FlightGear has had two release plans over history. The original release plan was developed by Mathias Fröhlich, Martin Spott, Thorsten Brehm and Torsten Dreyer during LinuxTag 2011. The current plan was proposed by Torsten Dreyer after the 3.6 release was cancelled.

To suggest improvements and/or changes to the release plan, it is recommended to get in touch via the mailing list. Improvements can be based on the lessons learned from previous releases.

General release concept (old release plan)

New FlightGear releases are scheduled twice a year. The magic number to remember is 17. On the 17th of January (the first month) and July (the seventh month), a new release branch is created for SimGear, the FlightGear source, and fgdata.

Cquote1.png As a clarification: We do not enter a code freeze but a feature freeze. Code changes are welcome after December 17th as long as it is guaranteed (not just "unlikely") that they do not introduce any side effects and become a release blocker. It is the sole responsibility of the committer to decide if that is the case or not. Every new feature that didn't make it into the repository by the deadline may probably easily wait for another four weeks to get committed. Remember: most aircraft are not affected by the feature freeze and aircraft developers quickly adopt and use new features as they become available
— Torsten Dreyer (16th Nov 2012). [Flightgear-devel] Next FlightGear release (Feb. 17 2013).

After branching, there is one month for bug fixing in the release branch, so building and packing of the binaries and fgdata takes place around the 18th of February and the 18th of August. Allowing a few days for distribution of the files, new versions should be publicly available around the 20th of February and August.

The development stream of SimGear, FlightGear, and fgdata is set into a frozen state one month before the branch-day (17th), to let the dust of development settle and to allow fixing the most annoying bugs in the code. During this period, developers should not add any new features, subsystems, and the like. Immediately after the stream has branched for the release, development in the main stream (next/master) is open for major changes until one month before the next branch-day. This results in a duty cycle of 5 month developing and 1 month thinking.

Version numbers

FlightGear version numbers consist of three digits, separated by dots:

Before 2016.1

  • Major (3.4.0): Only increased after significant changes to the functionality of the software (e.g., 1.x.x → 2.0.0 (due to switch to OSG).
  • Minor (3.4.0): Has two applications:
    • Stable releases always have even numbers (e.g. 2.8.0, 2.10.0, 2.12.0).
    • The latest Git version or nightly build uses an odd number, always one more than the latest stable release's minor revision numbere. For example, when the latest release was 3.4.0, the current development stream was 3.5.0.
  • Revision (3.4.0): Increased by bugfix releases (e.g., 2.12.1).

2016.1 and after

  • Year (2016.1.0): The year the version was released.
  • Number (2016.1.0): Which release of the year the version is (note: starts at 1).
  • Revision (2016.1.0): Indicates one of two things:
    • In the latest Git version or nightly build, this digit is 0, indicating that it is unstable.
    • When a new release is created, this digit is set to 1. With bugfix that is made, this digit is increased by 1, and a new version created.
Note  In general, release are referred to by their first two digits (e.g., 3.4). However, when filing a bug report or debugging problems, it is a good idea to give the full release number.

Detailed time schedule and checklist

  1. (On the 17th of the release month): The first Jenkins script is triggered to create release/xxxx.x.0 branches with version xxxx.x.0.
  2. Jenkins creates the binaries for xxxx.x.1.
  3. Patches going into the release/xxxx.x.0 branch automatically trigger a new build with a increase of the revision version number (see above) and we immediately have a bugfix release.
  4. On the next branch, the version number is changed.
  5. Nightly builds are created from next after every push in that branch.

The process is repeated after a set number of months (to-be-decided).

Version files


Bug tracking

The bugtracker is the primary source of bug reports. Unlike the forum or mailing list, bugs reported there will be tracked, making it easier for developers to. When reporting bugs, it is best to provide as muh information as possible to more easily find the bug.

Lessons learned

See Release plan/Lessons learned for a list of things that turned out well and should be kept for the next release as well as thing that didn't turn out so well and should be changed for future releases. Ideally, the release plan should be updated and augmented so that the lessons learned are incorporated accordingly.

Related content

Mailing lists