Release plan

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Revision as of 20:17, 31 January 2013 by Hooray (Talk | contribs) (2.10)

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Current release: 2020.1 (11 May 2020)
Next release: 2020.2 (109 days from now)
See release plan for details.

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 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 exist of three digits, seperated by dots:

  • Major (2.4.1): is only increased after significant changes to the functionality of the software, i.e. 1.X.X => 2.0.0 (due to switch to OSG).
  • Minor (2.4.1): has two applications:
    • Stable releases always have even numbers, i.e. 2.6.0, 2.8.0, 3.0.0.
    • The development stream (latest Git version) uses an odd number, increasing the minor number of the latest stable release's version by one. I.e., when the latest release is 2.8.0, the current development stream is 2.9.0.
  • Revision (2.4.1): is increased by bugfix releases, i.e. 2.8.1, 2.8.2, 2.8.3.

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. modify options.cxx to bump the hard-coded base package version number in [1]
    6. Compile and test drive FlightGear with the new version-number
    7. Commit the new version number to next (flightgear+simgear) and master(fgdata)
    8. Tag (annotated) flightgear, simgear and fgdata with version/3.0.0
      git tag -a version/3.0.0 (Enter a wise comment)
    9. 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
    4. Core developers and other contributors should be invited to add their release related experiences (i.e. suggestions for improvements) to the wiki to help update and improve the release plan (i.e. this page) accordingly.

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

State Description
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

The following table should be updated and augmented after each release, according to the Lessons learned section below.

Task Owner(s) Status for 2.10.0
Announce the state-change of the dev-streams TorstenD Done Done
Create/maintain the git branches TorstenD Done Done
Track the bugs on the tracker, trigger developers, adjust bug-priorities ThorstenB, Gijs, James, ...
Sync the language files so they can be translated ThorstenB, James Done Done
Beta testing EVERYBODY
Update documentation: FAQ, The Manual, wiki Stuart, Gijs and anyone else Done Done
Pack RC and final version of FGDATA
Create the RC and final version Source-tarball Curt
Linux ThorstenB (for openSUSE)
Windows Curt Done Done [2]
MacOS Tat/James Done Done [3]
Distribute files to download servers Curt 30}% completed
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 and/or document the creation of RC's: "We need to get this automated some day. Or at least documented...(another one from "famous last words": if you have to do it more than once, automate it. If you can't automate it, document it." [4]
  • Automate the creation of Windows and Mac installers
  • Automate the creation of FGDATA distribution
  • Possibly try to find a way to automate testing of updated jsbsim code, so that the chance for breakage is reduced by running scripted tests [5]

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 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.


  • FlightGear Core related :
    • perform a sync with JSBSim sources before the feature freeze.
    • there were a number of navcache/SQLite related issues reported via the issue tracker and the forum/devel list [6] [7]
    • a little irritation/frustration was caused due to the conflicting review statements concerning the new radio propagation code [8] [9] [10] - some of this boiled down to coding style related issues, highlighting the fact that different core developers have different "coding styles" and requirements when reviewing merge requests, because we still lack an official "FlightGear coding style guide" [11]

  • Changelog / Release Announcement:
    • Thumbs up icon Walking through the list of "lessons learned" as part of the "Upcoming release" announcement was useful [12]
    • Probably it would be even better to directly process all "lessons learned" items and improve the release plan after each release accordingly
    • To get to the 3.0 goal sometime in the near future, it's probably a good idea to create a backlog of open items in the wiki and link the release plan document to that. As usual, we don't have to be perfect for a new major release number. But the new features being the reason for the new major number should work reasonably correct. [13] (also see Category:Developer Plans)
    • Thumbs up icon Posting the link to the changelog for the upcoming release helped writing the changelog early, this should also be done for the Hardware Recommendations and Notebooks known to run FlightGear pages probably?
    • Thumbs up icon The changelog can be easily written by using "git log", searching the issue tracker and by going through the last 6 newsletters published since the previous release. It might make sense to explicitly add a "ChangeLog" message to important commits, so that the Changelog can be compiled more easily ?
    • Alternatively, request developers to add major changes also to $FG_SRC/ChangeLog again (last updated in 2001)?
    • for the web-based release announcement, it would be helpful to have screen shots or even youtube videos to demonstrate new features
    • it may make sense to also allow artwork contributors to contribute new splash screen images for use in the upcoming release. The screen shot contest should provide plenty of options [14].
    • The RC announcement should also contain links to 1) the issue tracker and 2) the RC subforum [15]
    • Using wiki tagging, we could ensure that we can also tag our wiki documentation after each release, so that we can provide older versions of our docs for old FG versions [16]
  • Shaders:
    • Thumbs up icon lowering the default shader level to 1 improved compatibility for older/underpowered systems [17]
    • GLSL shaders and effects should be treated like core code, and should be tested on different platforms before being enabled by default (i.e. signed-off by people using NVIDIA, ATI/AMD, Intel) [18]
    • modified shaders should be tested with other shader-related features to prevent breakage [19] (there might be a way to automate this a litle by catching GLSL compiler errors?)
    • to address all the intel GPU related issues, we may want to show an info dialog on computers where /sim/rendering/gl-vendor contains "intel" as a substring and provide an option to disable all shaders [20]
  • FGData related (Base Package):
    • Language files should be synced between English and other languages, so translators can work on them before the release ;-)
    • the script in $FG_SRC/scripts/python should be run as part of the release process, to create an updated doc file for $FG_ROOT/Docs and ship it with each release [21]
    • New/updated Nasal scripts contributed to the base package should be checked to properly support important features like simulator reset, this also applies to Nasal scripts used by aircraft, Nasal scripts that fail these criteria, end up breaking existing features! [22] (also see Release:Aircraft Selection Criteria)
    • Thumbs up icon regarding aircraft included in the release: "I must stress usefulness of the Autostart feature, present in most aircraft not running at startup. It keeps frustration away from those who just want to enjoy the flight . (Please note that I actually agree with aircraft being shut down at startup, as long as autostart is present, or the starting procedure is trivially doable by just trying what you see in the cockpit.) " [23] (also see Release:Aircraft Selection Criteria)
    • Thumbs up icon also, it would apparently make sense to provide tutorials for the default aircraft: "At first startup, I noticed the "Need help? use help->tutorials" message, and because I had no idea how to start up the plane (it would be just plain try and fail, than try something else), I did just that and started some basic tutorials. I wouldn't say going through the tutorials was frustrating, but they were quite boring and I was eager to get in the air as soon as possible." [24] (also see Release:Aircraft Selection Criteria)
    • "I discovered however, that there can be some problems on Linux about the planes (eg. some versions of the L39 Albatros undergoing several improvements lately). The problems can be caused by Linux being case sensitive about file paths (Windows is not), and I suspect, more models could suffer from some developers not knowing that. It's easy to fix if you know about the problem, but it would better be done on the developer side, as you never know if the smoke is just not implemented or missing due to this. Not to mention how lengthy it would be to go through more aircraft..." [25]
    • The installer should be updated to show a warning regarding TerraSync update time [26]
  • Usability:
    • Thumbs down icon A little downside is how the FGcom is done as a standalone program just cooperating with FG itself. It took me some fiddling with the settings for about two hours to get it working, but again installation was simply done from repos (FGcom and than FGcomGui as well). [27] (this is planned [28])
    • Thumbs down icon Most likely because of the Intel graphics, I suffered for a long time from a problem with aircraft models (and some ground textures too) being black or missing some parts (see my post in an older thread complaining about similar problem). I solved it by adding a command line option turning off texture compression. [29] (also see Release:Aircraft Selection Criteria)
    • I also vote for hosting a non-GPL hangar on the FG site, and tighter coordination with the aircraft developers (I think they should be asked to actively propose their models to the hangar once it is created, of course there could be link to their site/hangar). It would help nice models to be more easily found, an more people could enjoy them. And that's why people spend time creating them, right? [30]
    • We should probably add a new menu to the menubar for our online resources (wiki, forum, issue tracker, FAQ) so that people more easily find important resources just by selecting them from a menu.
  • Release Candidates:
    • Release Candidates should probably have a higher default logging level while writing everything to a log file that can be easily shared via the issue tracker/forums, so that end users can provide better bug reports.
    • How about having a test run a week or two in advance, just to make sure we can indeed produce release installers for Win+Mac - and then release the first RC on December 17th/18th or 19th [31]
    • We've already got a fairly extensive lead-in time for the release. More testers on more platforms would seem to be the answer. Perhaps we should advertize for testers of those platforms that aren't adequately covered by developers running git? Making a complete package available, not just the binaries would help, as testers wouldn't need to be git-aware. [32]
    • The main area to improve is to distribute release candidates for all platforms earlier - preferably starting immediately after the freeze. That would already give us more time for testing - without extending the actual freeze period.[33]
    • aircraft packages should be prepared prior to the official release date: "For the 2.8 release I didn't start making aircraft download packages (or uploading them to the ftp servers) until after the official release date which was a mistake" [34]
    • RC's should probably be built with Built-in Profiler support enabled [35].
    • When releasing RC's do not limit them to Win/Mac binaries, but also create source snapshots so that distros can already work on the next package versions.
    • For RC's it might make sense to distribute binaries with debugging symbols included and profiling support enabled, so that people can more easily provide useful bug reports, or even backtraces.
    • Also, many end users still prefer using the forum for making bug reports and don't use the issue tracker - it might help to add a link (button) to the issue tracker to the about dialog or maybe even directly to the help menu ("Report an issue") (same for wiki/troubleshooting/faq ?)
    • it might make sense to give wider exposure to our RCs, i.e. via the newsletter - possibly by adjusting the release schedule
  • Build related:
  • A normal Linux user has practically no chance to get last stable on his box running if it isn't in his distro - a normal Windows user gets everything nice and streamlined. [36]
  • According to the issue tracker there were 3-5 different contributors who provided C++ patches that didn't end up reviewed/merged, which caused some irritation.



  • 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.