[Avocado-devel] [RFC v4]: Long Term Stability (was Avocado maintainability and integration with avocado-vt)
Amador Segundo
asegundo at redhat.com
Thu Apr 27 08:04:23 UTC 2017
On Thu, Apr 27, 2017 at 1:07 AM, Cleber Rosa <crosa at redhat.com> wrote:
> ==========================
> RFC: Long Term Stability
> ==========================
>
> This RFC contains proposals and clarifications regarding the
> maintenance and release processes of Avocado.
>
> We understand there are multiple teams currently depending on the
> stability of Avocado and we don't want their work to be disrupted by
> incompatibilities nor instabilities in new releases.
>
> This version is a minor update to previous versions of the same RFC
> (see `Changelog`_) which drove the release of Avocado 36.0 LTS. The
> Avocado team has plans for a new LTS release in the near future, so
> please consider reading and providing feedback on the proposals here.
>
> TL;DR
> =====
>
> We plan to keep the current approach of sprint releases every 3-4
> weeks, but we're introducing "Long Term Stability" releases which
> should be adopted in production environments where users can't keep up
> with frequent upgrades.
>
> Changelog
> =========
>
> Changes from `Version 3`_:
>
> * Converted formatting to REStructuredText
> * Replaced "me" mentions on version 1 changelog with proper name
> (Ademar Reis)
> * Renamed section "Misc Details" to `Deployment Details`_
> * Renamed "avocado-vt" to "Avocado-VT"
> * Start the timeline example with version 36.0
> * Be explicit on timeline example that a minor bug did not generate
> an immediate release
>
> Changes from `Version 2`_:
>
> * Wording changes on second paragraph ("... nor instabilities...")
> * Clarified on "Introduction" that change of behavior is introduced
> between regular releases
> * Updated distro versions for which official packages are built
> * Add more clear explanation on official packages on the various
> hardware platforms
> * Used more recent version numbers as examples, and the planned
> new LTS version too
> * Explain how users can get the LTS version when using tools such as
> pip
> * Simplified the timeline example, with examples that will possibly
> match the future versions and releases
> * Documented current status of Avocado-VT releases and packages
>
> Changes from `Version 1`_:
>
> * Changed "Support" to "Stability" and "supported" to "maintained"
> [Jeff Nelson]
> * Misc improvements and clarifications in the
> supportability/stability statements [Jeff Nelson, Ademar Reis]
> * Fixed a few typos [Jeff Nelson, Ademar Reis]
>
> Introduction
> ============
>
> We make new releases of Avocado every 3-4 weeks on average. In theory
> at least, we're very careful with backwards compatibility. We test
> Avocado for regressions and we try to document any issues, so
> upgrading to a new version should be (again, in theory) safe.
>
> But in practice both intended and unintended changes are introduced
> during development, and both can be frustrating for conservative
> users. We also understand it's not feasible for users to upgrade
> Avocado very frequently in a production environment.
>
> The objective of this RFC is to clarify our maintenance practices and
> introduce Long Term Stability (LTS) releases, which are intended to
> solve, or at least mitigate, these problems.
>
>
> Our definition of maintained, or stable
> =======================================
>
> First of all, Avocado and its sub-projects are provided 'AS IS' and
> WITHOUT ANY WARRANTY, as described in the LICENSE file.
>
> The process described here doesn't imply any commitments or
> promises. It's just a set of best practices and recommendations.
>
> When something is identified as "stable" or "maintained", it means the
> development community makes a conscious effort to keep it working and
> consider reports of bugs and issues as high priorities. Fixes
> submitted for these issues will also be considered high priorities,
> although they will be accepted only if they pass the general
> acceptance criteria for new contributions (design, quality,
> documentation, testing, etc), at the development team discretion.
>
>
> Maintained projects and platforms
> =================================
>
> The only maintained project as of today is the Avocado Test Runner,
> including its APIs and core plugins (the contents of the main avocado
> git repository).
>
> Other projects kept under the "Avocado Umbrella" in github may be
> maintained by different teams (e.g.: Avocado-VT) or be considered
> experimental (e.g.: avocado-server and avocado-virt).
>
> More about Avocado-VT in its own section further down.
>
> As a general rule, fixes and bug reports for Avocado when running in
> any modern Linux distribution are welcome.
>
> But given the limited capacity of the development team, packaged
> versions of Avocado will be tested and maintained only for the
> following Linux distributions:
>
> * RHEL 7.x (latest)
> * Fedora (stable releases from the Fedora projects)
>
> Currently all packages produced by the Avocado projects are "noarch".
> That means that they could be installable on any hardware platform.
> Still, the development team will currently attempt to provide versions
> that are stable for the following platforms:
>
> * x86
> * ppc64
> * ppc64le
>
> Contributions from the community to maintain other platforms and
> operating systems are very welcome.
>
> The lists above may change without prior notice.
>
> Avocado Releases
> ================
>
> The proposal is to have two different types of Avocado releases:
>
> Sprint Releases
> ---------------
>
> (This is the model we currently adopt in Avocado)
>
> They happen every 3-4 weeks (the schedule is not fixed) and
> their versions are numbered serially, with decimal digits in
> the format <major>.<minor>. Examples: 47.0, 48.0, 49.0. Minor
> releases are rare, but necessary to correct some major issue
> with the original release (47.1, 47.2, etc).
>
> Only the latest Sprint Release is maintained.
>
> In Sprint Releases we make a conscious effort to keep backwards
> compatibility with the previous version (APIs and behavior) and
> as a general rule and best practice, incompatible changes in
> Sprint Releases should be documented in the release notes and
> if possible deprecated slowly, to give users time to adapt
> their environments.
>
> But we understand changes are inevitable as the software
> evolves and therefore there's no absolute promise for API and
> behavioral stability.
>
> Long Term Stability (LTS) Releases
> ----------------------------------
>
> LTS releases should happen whenever the team feels the code is
> stable enough to be maintained for a longer period of time, ideally
> once or twice per year (no fixed schedule).
>
> They should be maintained for 18 months, receiving fixes for major
> bugs in the form of minor (sub-)releases. With the exception of
> these fixes, no API or behavior should change in a minor LTS
> release.
>
> They will be versioned just like Sprint Releases, so looking at the
> version number alone will not reveal the differentiate release
> process and stability characteristics.
>
> In practice each major LTS release will imply in the creation of a
> git branch where only serious issues affecting users will be
> fixed. The code in a LTS branch is stable, frozen for new features.
I'd improve the sentence "only serious issues affecting users will be
fixed". In fact, we "backport" (meaning upstream first) "any issues"
(not only the serious ones) that are possible to be fixed *and* are
affecting users.
Not sure if it is also worth it to define 'backport'. Depending on the
code distance between the LTS and the master branch, it can be a
simple 'cherry-pick' or a completely different fix in terms of code,
as long as the bug gets fixed.
>
> Notice that although within a LTS release there's a expectation
> of stability because the code is frozen, different (major) LTS
> releases may include changes in behavior, API incompatibilities
> and new features. The development team will make a considerable
> effort to minimize and properly document these changes (changes
> when comparing it to the last major LTS release).
>
> Sprint Releases are replaced by LTS releases. I.e., in the cycle
> when 52.0 (LTS) is released, that's also the version used as a
> Sprint Release (there's no 52.0 -- non LTS -- in this case).
>
> New LTS releases should be done carefully, with ample time for
> announcements, testing and documentation. It's recommended
> that one or two sprints are dedicated as preparations for a LTS
> release, with a Sprint Release serving as a "LTS beta" release.
>
> Similarly, there should be announcements about the end-of-life
> (EOL) of a LTS release once it approaches its 18 months of
> life.
>
>
> Deployment details
> ==================
>
> Sprint and LTS releases, when packaged, whenever possible, will be
> preferably distributed through different package channels
> (repositories).
>
> This is possible for repository types such as `YUM/DNF repos`_. In
> such cases, users can disable the regular channel, and enable the LTS
> version. A request for the installation of Avocado packages will
> fetch the latest version available in the enabled repository. If the
> LTS repository channel is enabled, the packages will receive minor
> updates (bugfixes only), until a new LTS version is released (roughly
> every 12 months).
>
> If the non-LTS channel is enabled, users will receive updates every
> 3-4 weeks.
>
> On other types of repos such as `PyPI`_ which have no concept of
> "sub-repos" or "channels", users can request a version smaller than
> the version that succeeds the current LTS to get the latest LTS
> (including minor releases). Suppose the current LTS major version is
> 52, but there have been minor releases 52.1 and 52.2. By running::
>
> pip install 'avocado-framework<53.0'
>
> pip provide LTS version 52.2. If 52.3 gets released, they will be
> automatically deployed instead. When a new LTS is released, users
> would still get the latest minor release from the 52.0 series, unless
> they update the version specification.
>
> The existence of LTS releases should never be used as an excuse
> to break a Sprint Release or to introduce gratuitous
> incompatibilities there. In other words, Sprint Releases should
> still be taken seriously, just as they are today.
>
>
> Timeline example
> ================
>
> Assume each sprint is taking 3 weeks. Notice how multiple LTS
> releases can co-exist before EOL:
>
> 36.0
> * **LTS** release (the only LTS release available at the time of
> writing)
>
> 37.0 .. 49.0
> * sprint releases
>
> 50.0
> * sprint release
> * start preparing a LTS release, so 51.0 will be a **beta LTS**
>
> 51.0
> * sprint release
> * **beta LTS** release
>
> 52.0
> * **LTS** release
> * 52lts branch is created
> * packages go into LTS repo
> * both **36.x LTS** and **52.x LTS** maintained from this point on
>
> 53.0
> * sprint release
> * bug that also affects 52.0 is found, fix gets added to master and
> 52lts branches
Fix gets added to master and backported to supported LTS branches (at
this point, 52lts and 36lts).
>
> 54.0
> * sprint release 54.0 **AND** LTS 52.1 release
> * minor bug that also affects 52.0 is found, fix gets added to
> master and 52lts branches
Fix gets added to master and backported to supported LTS branches (at
this point, 52lts and 36lts).
>
> 55.0
> * sprint release
> * critical bug that affects 52.1 *only* is found, fix gets added to
> 52lts and 52.2 LTS is immediately released
>
> 56.0
> * sprint release
>
> 57.0
> * sprint release
>
> 58.0
> * sprint release
>
> 59.0
> * sprint release
> * EOL for **36.x LTS** (18 months since the release of 36.0)
>
> Avocado-VT
> ==========
>
> Avocado-VT is an Avocado plugin that allows "VT tests" to be run
> inside Avocado. It's a third-party project maintained mostly by
> Engineers from Red Hat QE with assistance from the Avocado team
> and other community members.
>
> It's a general consensus that QE teams use Avocado-VT directly
> from git, usually following the master branch, which they
> control.
>
> There's no official maintenance or stability statement for
> Avocado-VT. Even though the upstream community is quite
> friendly and open to both contributions and bug reports,
> Avocado-VT is made available without any promises for
> compatibility or supportability.
>
> When packaged and versioned, Avocado-VT rpms should be considered
> just snapshots, available in packaged form as a convenience to
> users outside of the Avocado-VT development community. Again,
> they are made available without any promises of compatibility or
> stability.
>
> * Which Avocado version should be used by Avocado-VT?
>
> This is up to the Avocado-VT community to decide, but the
> current consensus is that to guarantee some stability in
> production environments, Avocado-VT should stick to a specific
> LTS release of Avocado. In other words, the Avocado team
> recommends production users of Avocado-VT not to install Avocado
> from its master branch or upgrade it from Sprint Releases.
>
> Given each LTS release will be maintained for 18 months, it
> should be reasonable to expect Avocado-VT to upgrade to a new
> LTS release once a year or so. This process will be done with
> support from the Avocado team to avoid disruptions, with proper
> coordination via the avocado mailing lists.
>
> In practice the Avocado development team will keep watching
> Avocado-VT to detect and document incompatibilities, so when
> the time comes to do an upgrade in production, it's expected
> that it should happen smoothly.
>
> * Will it be possible to use the latest Avocado and Avocado-VT
> together?
>
> Users are welcome to *try* this combination. The Avocado
> development team itself will do it internally as a way to monitor
> incompatibilities and regressions.
>
> Whenever Avocado is released, a matching versioned snapshot of
> Avocado-VT will be made. Packages containing those Avocado-VT
> snapshots, for convenience only, will be made available in the
> regular Avocado repository.
>
> .. _Version 1:
> https://www.redhat.com/archives/avocado-devel/2016-April/msg00006.html
> .. _Version 2:
> https://www.redhat.com/archives/avocado-devel/2016-April/msg00038.html
> .. _Version 3:
> https://www.redhat.com/archives/avocado-devel/2017-April/msg00032.html
> .. _YUM/DNF repos:
> http://avocado-framework.readthedocs.io/en/latest/GetStartedGuide.html#fedora-from-avocado-s-own-repo
> .. _PyPI: https://pypi.python.org/pypi
>
>
> --
> Cleber Rosa
> [ Sr Software Engineer - Virtualization Team - Red Hat ]
> [ Avocado Test Framework - avocado-framework.github.io ]
> [ 7ABB 96EB 8B46 B94D 5E0F E9BB 657E 8D33 A5F2 09F3 ]
>
More information about the Avocado-devel
mailing list