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[[!meta title="DEP-10: parallelized ('rolling') release management"]]
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Title: parallelized ('rolling') release management"
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DEP: 10
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State: DRAFT
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Date: 2011-04-30
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Drivers: Sean Finney <seanius@debian.org>,
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Raphaël Hertzog <hertzog@debian.org>
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URL: http://dep.debian.net/deps/dep10
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License: GPL
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Abstract:
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Proposal for changes to release management methodology and infrastructure
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to remove the requirement that the testing suite must freeze during
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the release process.
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[[!toc ]]
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<a name="introduction">
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# Introduction / Problem scope
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Currently, as the project nears a new stable release, a freeze is instituted
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on the testing suite. The freeze is put in place to allow the release team
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to focus on resolving the remaining Release Critical (RC) bugs for the next
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stable release, and at the same time to prevent regressions from new uploads.
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Typically the freeze begins as an advisory "soft freeze", which over
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time increases in strictness and levels of enforcement.
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Unsuprisingly, as the strictness of the freeze increases, there is an
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inversely proportional decrease in other non-release targeted maintainer
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activity. Since unstable still is the preferred route for packages to
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reach the new release during this period, maintainers are highly discouraged
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and in some cases prevented from doing non-release targeted activities
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in unstable.
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The reduction of such non-release activity is viewed as problematic in
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this DEP, for some inter-related reasons:
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* New features and innovations are put on hold, or at least not commonly
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available, until after the release is made.
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* Overall Maintainer activity decreases as freezes persist.
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* Potential userbase is lost (missing feature X, switch distro).
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* The volatility of testing/unstable increases (and thus quality decreases)
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with a deluge of new uploads after the freeze is lifted.
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As Debian is well known for taking a "release when it's ready" approach, the
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freeze periods are generally known to last considerable amounts of time.
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Consider the last three freezes:
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* squeeze: 4 months
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* lenny: 7 months
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* squeeze: 6 months
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This means, in rough terms, that the when testing thaws, that the Debian
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project may be starting from a state half a year behind comparable
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distributions.
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While the resulting stable releases are well known for their high level
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of quality and stability, it is at a considerable cost. The project is,
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in essence, starting from a 6 month standstill, will be similarly
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out of date with comparable distributions. Furthermore, both the standstill
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as well as the subsequent rush of uploads will introduce further delays
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to the next release, as release goals will likely be set relative to
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the starting point.
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# Past and present release methods
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## Frozen (< 2000)
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Before the introduction of testing, Debian used a simple release process
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where the unstable suite was snapshotted into a `frozen` suite. This suite
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would then be used exclusively for preparing the next stable release, with
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unstable continuing in parallel.
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Before freeze Freeze Release
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[unstable/sid]--------------------------------------------------------------
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\
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[frozen].-.-.-.-.[stable/R_N].-.-.-.-.-.-.-.-.-.-.-.-.-.
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[stable/R_N-1].-.-.-.-.-.-.-.-.-.-.-.[oldstable/R_N-1].-.-.-(EOL)
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--------: Normal activity. Standard rules for uploads and migrations.
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.-.-.-.-: Release targeted activity. Freezes and limited uploads.
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\ \ \ \ : Package migration activity.
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### Use cases with `frozen`
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Users were divided into two sets, those using `unstable` and those using
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`stable`. Very few users would use both, as the two lines of development
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would quickly diverge from each other.
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### Benefits with `frozen`
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* Work in unstable continued, unaffected by the freeze.
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### Problems with `frozen`
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* Release work started from a buggy suite.
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* Duplicated effort in unstable/frozen.
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* RM had more work/responsibilities, and was prone to burn-out.
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## Testing (2000-Present)
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The testing suite was introduced in Debian between the release of potato
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and woody, in the fall of 2000[[1]]. The goal was to provide
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a suite that was in a better state for release preparation, by having
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both automated and manual tools to keep down the level of bugs and
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general volatility.
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As a pleasant and convenient side-effect, the new suite also provided
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a "slightly less buggy unstable" for developers and end-users, who wanted
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newer software/features not available in stable, but wanted some level
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of protection to the relatively unpredictable nature of unstable.
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Before release Freeze Release
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[unstable/sid]----------.--.--.--.-.-.-.-.-.-.------------------------------
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\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \
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[testing/R_N]----------.-.-.-.-.-.-.-.-.-.-.-.[testing/R_N+1]---------------
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/ / \
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/ / [stable/R_N].-.-.-.-.-.-.-.-.-.-.-
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/ / / / /
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[R_N p-u].-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-
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[stable/R_N-1].-.-.-.-.-.-.-.-.-.-.-.-.-.-[oldstable/R_N-1].-.-.-(EOL)
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--------: Normal activity. Standard rules for uploads and migrations.
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.-.-.-.-: Release targeted activity. Freezes and limited uploads.
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\ \ \ \ : Package migration activity. Spacing of marks is a rough
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indication of frequency.
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During the freeze, the testing suite becomes entirely dedicated to the
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release work. In practice, this also means that unstable is also to
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some extent frozen from non-release activity for many packages, since
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it still serves as the main route to testing for new uploads.
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### Use cases with `testing`
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The introduction of the new suite also introduced a type of continuum
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in which users now have more flexibility in selecting what to have installed.
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* `unstable`: only the "bleeding edge" of Debian updates.
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* `testing`: only the "leading edge" of Debian updates.
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* `testing/unstable`: A hybrid solution of the two previous use cases,
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allowing for a reasonable balance between them.
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* `stable`: The latest stable release.
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* `stable/testing`: the stable release with perhaps some newer packages
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installed, typically also making use of "APT pins" to prevent unwanted
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upgrades. Less common now with the inclusion of backports and volatile
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as official Debian services.
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### Benefits with `testing`
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* Release branch has far fewer bugs at the start of the release process.
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* (Ideally) shorter release process with fewer problems.
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* Large user-base for testing stable-targeted fixes.
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### Problems with `testing`
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(See [Introduction](#introduction))
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[1]: http://lists.debian.org/debian-devel/2000/08/msg00906.html
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