Release plan

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Revision as of 14:35, 22 August 2012 by Hooray (talk | contribs) (→‎2.8)
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This page contains details about how to release a new version of FlightGear into the wild. It is a continous work in progress to be improved with every new release.

The original plan

This release plan was originally developed by Mathias Fröhlich, Martin Spott, Thorsten Brehm and Torsten Dreyer during LinuxTag 2011.

If you think you have something to contribute to the release process, feel free to edit this page. In particular, improvements should be based on Release plan#Lessons learned from past releases. Please discuss this concept at the mailing-list.

General release concept

New FlightGear releases are scheduled twice a year. The magic number to remember is 17 (we tried 42, but that didn't turn out so well. 17 is perfect: 1 is not a prime, 7 is a prime and so is 17). On the 17th of January (1) and July (7) a new release branch is created for SimGear, FlightGear and FGDATA.

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 February, 18th and August, 18th. Allowing a few days for distribution of the files, new versions should be publically 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 are requested not to add any new features, subsystems or alike. 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

  • Major releases always have even numbers as the second version element, i.e. 2.6.0, 2.8.0, 3.0.0.
  • Bugfix releases increase the least significant digit: 2.8.1, 2.8.2, 2.8.3.
  • The development stream (latest Git version) uses an odd number, increasing the second element of the latest stable release's version by 1: (latest release is 2.8.0 => current development stream is 2.9.0, next official release is 3.0.0).
  • The major version number is increased after significant changes to the functionality of the software (i.e. FG 1.x => 2.0 due to switch to OSG).

Detailed time schedule and checklist

  1. Dec/Jun 17th: Development stream is declared "frozen" or "yellow"
    1. Send a mail to the flightgear-devel mailing-list to announce the state
    2. Create a "release preperations" topic at the forum and make it a "Global Announcement"
    3. Change the content of wiki template at Template:GitStatus to {{GitStatus:frozen}}
    4. Bump up the version-number of simgear/next, flightgear/next and fgdata/master to an even number (2.9.0 -> 3.0.0)
    5. Compile and test drive FlightGear with the new version-number
    6. Commit the new version number to next (flightgear+simgear) and master(fgdata)
    7. Tag (annotated) flightgear, simgear and fgdata with version/3.0.0
      git tag -a version/3.0.0 (Enter a wise comment)
    8. Push the branches next/master and the tags upstream
      for flightgear and simgear: git push origin next
      for fgdata: git push origin master
      for the tags (all repos): git push origin version/3.0.0
  2. Jan/Jul 17th: Create new release branch, assign new version number to dev-stream, re-open streams
    1. Pull current Git, create the release branches (for sg/fg/fgdata):
      git pull
      git branch release/3.0.0
    2. On the next/master branches, bump up the version-number of simgear, flightgear and fgdata to an odd number (3.0.0 -> 3.1.0)
    3. Compile and test drive FlightGear with the new development version number
    4. Commit the changes of version-number to next/master
    5. Tag (annotated) flightgear, simgear and fgdata with "version/2.9.0"
      git tag -a version/2.9.0 (Enter a wise comment)
    6. Push the branches next/master and release/3.0.0 and the tags upstream
      for flightgear, simgear and fgdata: git push origin release/3.0.0
      for flightgear and simgear: git push origin next
      for fgdata: git push origin master
      for the tags (all repos): git push origin version/3.1.0
    7. Declare dev-streams "open" or "green"
      Ask a wiki admin to change the content of wiki template at Template:GitStatus to {{GitStatus:open}}
      Send a mail to the flightgear-devel mailing-list to announce the state.
    8. Trigger James for the Jenkins-builds and Curt for a snapshot release and ThorstenB for the OpenSuse build
  3. Feb/Aug 1st: Start preparing the release notes and a press announcement
  4. Feb/Aug 17th: Create binaries/installers, pack fgdata, publish files, announce new version, close the release-branch.
    1. Generate latest getstart.pdf, push the PDF to fgdata/master - and cherry-pick to the release branch. Generate latest getstart HTML, push PDF and HTML to the MapServer site.
    2. Tag the release/3.00 branches of simgear, flightgear and fgdata and push the tags.
      for flighgear, simgear and fgdata: git tag version/3.0.0-final
      for flighgear, simgear and fgdata: git push origin version/3.0.0-final
    3. Merge the branch release/3.0.0 into master (NOT next) for flightgear and simgear and push the branch
      We don't have a next branch for fgdata, no merging of the release branch here.
      for flighgear and simgear:
      git checkout -b master origin/master or git checkout master if you already have the local branch
      git merge version/3.0.0-final
      git push origin master

To bump up the version number

  • fgdata
    • edit the version file
  • SimGear
    • edit the version file
  • FlightGear
    • edit the version file

Definition of repository states

  • Traffic light green.png Open/Green
    Normal development of the code base and fgdata. Unrestricted (well, sort of) access to the streams. This state lasts for five month after the release branches were created.
  • Traffic light yellow.png Frozen/Yellow
    No new features or major changes shall be pushed onto the development streams (neither source nor data). This period is for preparing the code for the release and make sure there are no major issues. It lasts for four weeks until creation of the release branches.
    It's a good idea for aircraft developers to adhere to this rule. However, aircraft in FGDATA may be handled as an exception from the frozen state. Any change to aircraft may be pushed to the repository if it is guaranteed that this change does not affect any other aircraft or system and if no file outside the root directory of that specific aircraft is changed. Also, aircraft defined as part of the base package (e.g. the c172p) enter the frozen state and shall not undergo major changes in that period.
  • Traffic light red.png Closed/Red
    Nothing shall be pushed to the development streams (simgear, flightgear and fgdata). This state is for creating the release branches. It lasts for just a few hours on Jan 17th and Jul 17th around 12:00 UTC.

Bug fix committing policy

Fixes for bugs during the shakedown test of the release branch may be applied to the branches next or release/2.8.0. A fix goes into release/2.8.0 if the development of next has moved forward and this fix does not apply there. It also goes into the release branch if there will be a better fix for next. A fix goes into next if it is also solves an issue for the next version. Cherry-pick this commit into the release/2.8.0 branch.

DO NOT merge next into release/2.8.0 or vice versa. Most likely, there will be commits that are not welcome in or even break the other branch.

Bug tracking

The bugtracker will be our primary source for the bug fixing period. Bugs reported on the mailing list or forum will not be tracked! Reporters shall be requested to file a bug report at the bugtracker. Bugs shall be assigned a priority and a keyword to make the assignment to a developer easier. Bug reports that can't be confirmed or need more input from the reporter to get fixed will be assigned a new state "stalled" and only processed after more information has been provided. Bugs assigned a high priority will be downgraded, if no progress has been made over a certain amount of time. This is to prevent the release from being blocked by a bug that no developer is able (or willing) to fix. The only exception is "does not compile for one of the major platforms", which certainly is a release-blocker.

Bugs that were present in the latest stable release, and now considered "fixed", should be assigned a milestone label, corresponding with the upcoming stable release number. By doing so, they'll end up in the list of fixed bugs.

Tasks and owners

Task Owner(s)
Announce the state-change of the dev-streams TorstenD
Create/maintain the git branches TorstenD
Track the bugs on the tracker, trigger developers, adjust bug-priorities ThorstenB, Gijs, James, ...
Beta testing EVERYBODY
Update documentation: FAQ, The Manual, wiki Stuart, Gijs and anyone else
Pack RC and final version of FGDATA
Create the RC and final version Source-tarball Curt
Linux ThorstenB (for openSUSE)
Windows Curt
MacOS Tat
Distribute files to download servers Curt
Make adjustments on the web-site Collect/make screenshots for the gallery Curt
Generate aircraft page Curt, Gijs
Announce the new version to the public Write a changelog: Changelog 3.0.0 All developers
Contact flightsim websites and send them/link them to the "press announcement". See release promotion for a list of already-contacted and yet-to-contact websites/magazins. EVERYBODY

Open items, questions

  • Automate the creation of Windows and Mac installers
  • Automate the creation of FGDATA distribution

Lessons learned

This is a list of lessons learned from the previous releases, things that turned out well and should be kept for the next release as well as thing thad didn't turn out so well and should be changed for future releases.


(not yet released)


  • Thumbs down icon Lack of stress-testing: A number of users reported severe memory growth issues (with fgfs consuming as much as 14gb of RAM), many directly related to new features, such as random buildings: [1] [2] [3] [4] These could have probably been identified earlier by running FG for extended periods of time, and testing the shipped aircraft with the default KSFO scenery, and new features such as random buildings enabled.
  • Thumbs down icon Lack of graceful feature scaling: Several users with old graphics cards reported not being able to run FG 2.8 without crashing during startup, because the FG defaults didn't scale for old hardware [5]
  • Thumbs down icon Broken OSX downloads
  • Thumbs down icon Microsoft Redistributables were not shipped with the Windows installer
  • Thumbs down icon The changelog should be written as early as possible
  • The code freeze could probably be lifted for patches that are not normally enabled/used by any default code paths (or shipped aircraft) in a FlightGear release. This probably involves Nasal extension functions, fgcommands, telnet commands, but also custom hard coded instruments or instrumentation-related APIs (think Canvas). Basically, whenever there's no chance to break a release by committing a certain patch, because the code path will not be executed by default without explicitly enabling it. For 2.8, this also meant that the Nasal Canvas API could not be included due to the code freeze, which however wasn't used by any systems or aircraft - so that there would have been zero chance for breakage [6].
  • The wiki contains a number of resources to help new users with hardware decisions, such as Hardware Recommendations Notebooks known to run FlightGear and Supported Video Cards - these should probably be updated for each release several weeks in advance.


  • Thumbs up icon feature freeze in general
    helped a lot during release management. Kept the commit traffic low and thus helped identifying those commits required to pick into the release.
  • Thumbs down icon feature freeze for aircraft
    Technically, a feature freeze for aircraft is not necessary as long as this aircraft is not part of the base distribution and no common parts are affected. If it's guaranteed that the changes remain in FGDATA/Aircraft/MyAircraft and no other files are touched, these updates should be OK up to shortly before the release.
  • Thumbs down icon switching to a new version of supporting libraries like OSG.
    The move to OSG 3.x introduced some major issues. If at all possible, switch to a new library early in the development cycle.
  • Thumbs down icon manual creation of release candidates and the release binaries
    It's preferable to have equal numbers for release candidates for all O/S and probably a git-tag for each candidate.
  • Thumbs down icon release date/time frame
    It took several days to release all the subparts. Might be better to upload all files and pages to hidden folders and publish them all at once (or at least within a couple of hours). That'll have several advantages:
    • no big difference between releases for the various OS.
    • the website will switch to the new release state quickly. With 2.6.0, the aircraft page was published before the setup. The release announcement was published even later.