RFC: Package maintenance and update policy for EPEL -- take 1

[Thorsten Leemhuis]

Hi everyone,

find below my take for a "Package maintenance and update policy for 
EPEL". You an find it in the wiki at:
http://fedoraproject.org/wiki/EPEL/GuidelinesAndPolicies/PackageMaintenanceAndUpdates

If you spot typos (there are probably still some...) please fix them in 
the wiki directly -- that's why the document is there ;-)

Did I miss anything? Do people like the general direction?

CU
thl


= Package maintenance and update policy =

EPEL wants to provide a common "look and feel" to the users of our 
repository. Thus the EPEL SIG wrote this policy that describes the 
regulations for package maintenance and updates in EPEL, that are a bit 
more stronger regulated then they are in Fedora now.

[[TableOfContents]]

== Digest ==

The goal is to have packages in EPEL that enhances the Enterprise Linux 
distributions the packages were build against without disturbing or 
replacing packages from that distribution. The Packages in the 
Repository should if possible get maintained in similar ways like the 
packages get maintained in the Enterprise Linux Distribution they get 
build against. In other words: have a mostly stable set of packages that 
normally does not change at all and only changes if there are good 
reasons for it -- so no "hey, there is a new version, it builds, let's 
ship it" mentality.

== Policy ==

EPEL packages should only enhance and never disturb the Enterprise Linux 
distributions the packages were build for. Thus packages from EPEL 
should never replace packages from the base distribution they get build 
against; kernel-modules further are not allowed, as they can disturb the 
base kernel easily.

The Packages in the Repository should if possible get maintained in 
similar ways like the packages get maintained in the Enterprise Linux 
Distribution they get build against. In other words: have a mostly 
stable set of packages that normally does not change at all and only 
changes if there are good reasons for changes.

The changes that cant be avoided get routed into different release 
trees. Only updates that fix important bugs (say: data-corruption, 
security problems, really annoying bugs) go to a testing branch for a 
short time period and then build a second time for the stable branch; 
those people that sign and push the EPEL packages to the public repo 
will skim over the list of updated packages for the stable repo to make 
sure that sure the goal "only important updates for the stable branch" 
is fulfilled.

Other updates get queued up in a testing repository over time. That 
repository becomes the new stable branch in parallel with the quarterly 
update that get released by the Linux Distributor that creates the 
Enterprise Linux the packages gets build against. There will be a short 
freeze time period before the quarterly update happens to make sure the 
repo and its packages are in a good shape. But even this updates should 
be limited to fixes only as far as possible and should be tested in 
Fedora beforehand if possible. Updated Packages that change the ABI or 
require config file adjustments must be avoided if somehow possible. 
Compat- Packages that provide the old ABI need to be provided in the 
repo if there is no way around a package update that changes the ABI.

== Guidelines and Backgrounds for this policy ==

=== Some examples of what package updates that are fine or not ===

Examples hopefully help to outline how to actually apply above policy in 
practise.

==== Minor version updates ====

Let's assume package foo is shipped in EPEL 5.0 as version 1.0.1; 
upstream developers now ship 1.0.2

  * build for the stable branch only if it fixes serious bugs
  * build for the testing branch (which will be 5.1 later) is acceptable 
if the upstream release is mostly a bugfix release without new features 
and the package got run-time testing

==== A little bit bigger minor version updates ====

Let's assume package foo is shipped in EPEL 5.0 as version 1.0.1; 
upstream developers now ship 1.2.0; the ABI is compatible to 1.0.1 and 
the existing config files continue to work

  * build for the stable branch only if it fixes a really serious bug
  * build for the testing branch (which will be 5.1 later) is acceptable 
if it fixes serious bugs

==== A yet again little bit bigger minor version updates ====

Let's assume package foo is shipped in EPEL 5.0 as version 1.0.1; 
upstream developers now ship 1.4.0; the ABI is compatible to 1.0.1, but 
the config files need manual adjustments

  * build for the stable branch is normally not acceptable; a backport 
should be strongly considered if there are any serious bugs that must be 
fixed
  * build for the testing branch (which will be 5.1 later) is also 
disliked; but it is acceptable if there is no other easy way out to 
solve serious bugs; but the update and the config file adjustments need 
to be announced to the users properly -- say in form of release notes 
that get published together with the quarterly announcement.

==== A major version update ====

Let's assume package foo is shipped in EPEL 5.0 as version 1.0.1; 
upstream developers now ship 2.0.0; the ABI changes or the config files 
need manual adjustments

  * this update should be avoided if possible at all. If there really is 
no other way out to fix a serious bug then it rare cases it might be 
acceptable to build the new version for the testing branch and mention 
the update and the needed adjustments in the release notes for the next 
update. An additional compat- packages with the old libs is necessary if 
the ABI changed.

==== Add more examples as they show up ====

If to many show up put them into a separate document.

=== Why not a rolling release with up2date packages like Extras? ===

Why should we? That would be what Fedora (Extras) did and worked and 
works well for it -- but that's mainly because Fedora (Core) has lots of 
updates and a nearly rolling-release scheme/quick release cycle, too. 
But the Enterprise Linux we build against is much more careful with 
updates and has longer life-cycle; thus we should do the same for EPEL, 
as most users will properly prefer it that way, as they chose a stable 
distro for some reasons -- if they want bleeding edge they might have 
chosen Fedora.

Sure, there are lots of areas where having a mix of a stable base and a 
set of quite new packages on top of it is wanted. *Maybe* the EPEL 
project will provide a solution (in parallel to the carefully updated 
repository!) for those cases in the long term, but not for the start. 
BTW, there are already repositories out there that provide something in 
this direction, so users might be served by them already.

Further: A rolling release scheme like Fedora (Extras) did/does is not 
possible for many EPEL packages for another reason, too. New Packages 
often require new versions of certain core libraries, too. But we we 
can't provide them in EPEL, as they would replace/disturb stuff from the 
base distribution.

Example: This document was written round about when RHEL5 got released; 
many packages that get build for RHEL5 can't be build for RHEL4 at this 
point of time already, as the RHEL4-gtk2-Package is much two years old 
and way to old for many current applications, as they depend on a newer 
gtk2. So if even if we would try to have a rolling scheme with with 
quite new package we'd fail, as we can't build a bunch of package due to 
this dependencies on libs; in the end we would have a repo with some 
quite new packages while others are still quite old. That mix wouldn't 
make either of the "latest versions" or "careful updates only" sides 
happy; so we try to target the "careful updates only" sides.

=== How will the repo actually look like ===

Similar to what [ http://ftp-stud.fht-esslingen.de/pub/Mirrors/centos/ 
layout] CentOS uses. Rough example:

{{{
* epel/                         # topdir
  * 4/                           # topdir for EPEL4
   * 4 -> 4.5                    # symbolic link to latest version
   * 4.1/                        # this tree of course will never 
exists, as this is history, and is here just to show the example
   ....                          # 4.2, 4.3, 4.4; those won't ever 
exists, too
   * 4.5/                        # 4.5, latest version, build target: 
fedora-epel-4-stable
   * 4.6                         # not yet
   * ....                        # time will come
   * testing/                    # testing repo, that together with the 
old packages that didn't get update becomes 4.6 when RHEL 4.6
                                 # releases; build target: 
fedora-epel-5; gets frozen for a week or two before the quarterly update is
                                 # issued; new packages land here for a 
while, too

  * 5/                           # topdir for EPEL4
   * 5 -> 5.0                    # symbolic link to latest version
   * 5.0/                        # 5.0, latest version, build target: 
fedora-epel-5-stable
   * 5.1                         # not yet
   * ....                        # time will come
   * testing/                    # testing repo, that together with the 
old packages that didn't get update becomes 4.6 when RHEL 4.6
                                 # releases; build target: 
fedora-epel-5; gets frozen for a week or two before the quarterly update is
                                 # issued; new packages land here for a 
while, too
}}}

This layout may looks complicated, but has one major benefit: Users can 
stick to a EPEL repo for a not up2date EL release while a newer EL 
quarterly update is already out (some users do that on purpose, others 
have no chance as for example the CentOS update gets normally released 
up to four weeks after RHEL released a quarterly update). The above 
layout can makes it possible to prevent that users run into dependency 
issues that might arise otherwise if packages in the new EPEL release 
depend on new packages in the new EL release. The EPEL quarterly update 
further isn't forced on users before they switch to the quarterly update.

Each repo always has all the packages in it; hardlinks will be used to 
keep the space requirements on the server-side limited, as most packages 
won't change.