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- APACHE 2.x VERSIONING
- =====================
- [$LastChangedDate: 2005-10-17 17:17:21 +0000 (Mon, 17 Oct 2005) $]
- INTRODUCTION
- ------------
- The Apache HTTP Server project must balance two competing and disjoint
- objectives: maintain stable code for third party authors, distributors and
- most importantly users so that bug and security fixes can be quickly adopted
- without significant hardship due to user-visible changes; and continue the
- development process that requires ongoing redesign to correct earlier
- oversights and to add additional features.
- The Apache HTTP Server, through version 2.0, used the Module Magic Number (MMN)
- to reflect API changes. This had the shortcoming of often leaving users
- hunting to replace binary third party modules that were now incompatible.
- This also left module authors searching through the API change histories to
- determine the exact cause for the MMN change and whether their module was
- affected.
- With the simultaneous release of Apache 2.2-stable and Apache 2.3-development,
- the Apache HTTP Server project is moving towards a more predictable stable
- release cycle, while allowing forward progress to occur without concern
- for breaking the stable branch. This document explains the rationale between
- the two versions and their behavior.
- STABLE RELEASES, 2.{even}.{revision}
- ------------------------------------
- All even numbered releases will be considered stable revisions.
- Stable revisions will retain forward compatiblity to the maximum
- possible extent. Features may be added during minor revisions, and
- features may be deprecated by making appropriate notations in the
- documentation, but no features may be removed.
- In essence, that implies that you can upgrade from one minor revision
- to the next with a minimum of trouble. In particular, this means:
- * The Module API will retain forward compatibility.
- It will not be necessary to update modules to work with new
- revisions of the stable tree.
- * The run-time configuration will be forward compatible.
- No configuration changes will be necessary to work with new
- revisions of the stable tree.
- * Compile-time configuration will be forward compatible.
- The configure command line options that work in one release
- of the stable tree will also work in the next release.
- As always, it will be necessary to test any new release to assure
- that it works correctly with a particular configuration and a
- particular set of modules, but every effort will be made to assure
- that upgrades are as smooth as possible.
- In addition, the following development restrictions will aid in
- keeping the stable tree as safe as possible:
- * No 'Experimental' modules; while it may be possible (based on API changes
- required to support a given module) to load a 2.3-development module into
- a 2.2-stable build of Apache, there are no guarantees. Experimental
- modules will be introduced to the 2.3-development versions and either
- added to 2.2-stable once they are proven and compatible, or deferred
- to the 2.4-stable release if they cannot be incorporated in the current
- stable release due to API change requirements.
- * The stable subversion tree should not remain unstable at any time. Atomic
- commits aught be used to introduce code from the development version to the
- stable tree. At any given time a security release may be in preparation,
- unbeknownst to other contributors. At any given time, testers may be
- checking out SVN trunk to confirm that a bug has been corrected. And as
- all code was well-tested in development prior to committing to the stable
- tree, there is really no reason for this tree to be broken for more than
- a few minutes during a lengthy commit.
- In order to avoid 'skipped' release numbers in the stable releases, the
- Release Manager will generally roll a release candidate (APACHE_#_#_#_RC#)
- tag. Release Candidate tarballs will be announced to the
- stable-testers@httpd.apache.org for the stable tree. Then, the participants
- will vote on the quality of the proposed release tarball.
- The final APACHE_#_#_# tag will not exist until the APACHE_#_#_#_RC# candidate
- has passed the usual votes to release that version. Only then is the final
- tarball packaged, removing all -rc# designations from the version number, and
- tagging the tree with the release number.
- DEVELOPMENT RELEASES, 2.{odd}.{revision}
- -----------------------------------------
- All odd numbered releases designate the 'next' possible stable release,
- therefore the current development version will always be one greater than
- the current stable release. Work proceeds on development releases, permitting
- the modification of the MMN at any time in order to correct deficiencies
- or shortcomings in the API. This means that modules from one development
- release to another may not be binary compatible, or may not successfully
- compile without modification to accomodate the API changes.
- The only 'supported' development release at any time will be the most
- recently released version. Developers will not be answering bug reports
- of older development releases once a new release is available. It becomes
- the resposibility of the reporter to use the latest development version
- to confirm that any issue still exists.
- Any new code, new API features or new ('experimental') modules may be
- promoted at any time to the next stable release, by a vote of the project
- contributors. This vote is based on the technical stability of the new
- code and the stability of the interface. Once moved to stable, that feature
- cannot change for the remainder of that stable release cycle, so the vote must
- reflect that the final decisions on the behavior and naming of that new
- feature were reached. Vetos continue to apply to this choice of introducing
- the new work to the stable version.
- At any given time, when the quality of changes to the development branch
- is considered release quality, that version may become a candidate for the
- next stable release. This includes some or all of the API changes, promoting
- experimental modules to stable or deprecating and eliminating older modules
- from the last stable release. All of these choices are considered by the
- project as a group in the interests of promoting the stable release, so that
- any given change may be 'deferred' for a future release by the group, rather
- than introduce unacceptable risks to adopting the next stable release.
- Third party module authors are strongly encouraged to test with the latest
- development version. This assures that the module will be ready for the next
- stable release, but more importantly, the author can react to shortcomings
- in the API early enough to warn the dev@httpd.apache.org community of the
- shortcomings so that they can be addressed before the stable release. The
- entire burden is on the module author to anticipate the needs of their module
- before the stable release is created. Once a new stable release cycle has
- begun, that API will be present for the lifetime of the stable release. Any
- desired changes in the stable versions must wait for inclusion into the next
- release cycle.
- When deciding to promote a development tree to being stable, a determination
- should be made whether the changes since the last stable version warrant a
- major version bump. That is, if 2.2 is the current stable version and 2.3 is
- 'ready' to become stable, the group needs to decide if the next stable
- version is 2.4 or 3.0. One suggested rule of thumb is that if it requires
- too much effort to port a module from 2.2 to 2.4, then the stable version
- should be labeled 3.0.
- In order to ease the burden of creating development releases, the process
- for packaging a development releases is less formal than for the stable
- release. This strategy reflects the fact that while in development, versions
- are cheap. Development releases may be classified as alpha, beta, or GA
- to reflect the group's perceived stability of the tree. Development releases
- may be made at any time by any committer.
- Please read the following link for a more detailed description of the
- development release strategy:
- http://httpd.apache.org/dev/release.html
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