+1 (binding) Enrico
Il Mar 14 Feb 2023, 07:51 <mattisonc...@gmail.com> ha scritto: > +1(non-binding) > > Best, > Mattison > On Feb 9, 2023, 04:44 +0800, Matteo Merli <matteo.me...@gmail.com>, wrote: > > https://github.com/apache/pulsar/issues/15966 > > > > > ---------------------------------------------------------------------------------------- > > > > > > ## Motivation > > > > In PIP-47 ( > > https://github.com/apache/pulsar/wiki/PIP-47:-Time-Based-Release-Plan), > we > > have adopted a time-based release plan. This was the first attempt at > > establishing a new principle on how releases should b > > > > The main two benefits of this approach have been: > > > > 1. Clarity for users and developers on when to expect a release > > 2. Breaking a hard relationship between feature and release: a particular > > feature will be included in the release if it is completed in time. > > Otherwise, it will be bubbled up to the next release. > > > > The motivation for the current proposal is to extend the existing process > > to address the issues that we have seen and that were left out of the > scope > > of PIP-47. > > > > ## Summary of existing issues in the process > > > > ### Short maintenance cycles for releases > > > > Since we're doing a 3 months release cycle, we are ending with 4 releases > > done per year, even though it's more close to 3 releases. > > > > There is a high cost to maintain a lot of old releases, backport bug > fixes, > > and security patches. In general, we actively support the last 3 minor > > releases while continuing to develop the next release. E.g., 2.8, 2.9, > and > > 2.10, while 2.11 is under development. > > > > The result is that a user adopting a particular release is forced to > > upgrade in a < 1-year timeframe to keep up to date and use a supported > > release. This timeframe is too short for many users as it imposes a lot > of > > forced upgrades, for which they are not prepared in terms of available > time > > and required effort. > > > > ### Live Upgrade/Downgrade compatibility path > > > > In Pulsar, we guarantee that users have a way to do live upgrades and > > downgrades with zero downtime. > > > > This is very powerful because it gives them the freedom to upgrade to a > new > > release with the assurance of being able to roll back to the previous > > release in case any functional or performance regressions are > encountered. > > > > Today, this compatibility is guaranteed across minor versions. Eg: I can > do > > `2.7 -> 2.8 -> 2.7` as a live upgrade. > > > > What is not guaranteed is to "skip" releases. E.g.: `2.7 -> 2.9` might > work > > or not, but it's not guaranteed. In that case an intermediated upgrade > > would be required: `2.7 -> 2.8 -> 2.9`. > > > > The reasons for which the "skip" upgrade might not work are multiple: > > 1. Incompatible upgrade of some dependency (e.g., ZooKeeper) that might > > not be compatible with an older version. > > 2. Adoption of a new metadata format or data format on disk. > > Every time we introduce a new incompatible format change (outside of a > > regular Protobuf field addition), we do it in a 2 steps way: > > - In a new release, we introduce the new feature/format, disabled by > > default. The new release can read both old and new formats, though it > keeps > > writing the old format by default. > > - In a subsequent release, we change the default to the new format > > > > Note that this consideration is separate from the compatibility between > > clients and brokers, where we ***never*** break compatibility. The oldest > > available Pulsar client can still talk with the newest Pulsar broker, and > > vice versa, a new client, will be perfectly fine with an older broker > > (except the new features won't be working). > > > > ### Releases getting delayed > > > > Another problem we have been experiencing is that release cycles have > been > > stretching considerably. Part of this has been because we have been > > reaching the end of the release window, preparing a candidate, and then > > taking a long time to flush out all issues found at the last minute in > the > > new release. > > > > We need to ensure that we have a date set in stone to deliver the release > > to users. > > > > ## Proposal > > > > The proposal to address the above issues is composed of 2 parts. > > > > ### 1. Establish Long Term Support releases > > > > We need to provide a way for users to quickly understand the expected > > lifecycle timeline of a given release and for that timeline to be long > > enough not to be a constant update mandate. > > > > At the same time, we need to ensure that we maintainers are not spending > > all the time just maintaining a huge list of old releases. > > > > For that, we can use the established concept of "Long Term Releases" or > > LTS. > > > > We will perform LTS releases at a fixed cadence every 18 months, and we > > will keep doing regular feature releases every 3 months as we're > currently > > doing. > > > > The LTS releases will be identified by being a `.0` version. For example: > > * `3.0` -> LTS > > * `3.1` -> regular release > > * `3.2` -> regular release > > * `4.0` -> LTS > > > > The major version bump will not carry any special meaning in terms of > "big > > features" included in the release or breaking API changes. Instead, it > > would simply signal the type of the release. > > > > #### Compatibility between releases > > > > It will be guaranteed to be able to do a live upgrade/downgrade between > one > > LTS and the next one. > > > > For example: > > > > * `3.0 -> 4.0 -> 3.0` : OK > > * `3.2 -> 4.0 -> 3.2` : OK > > * `3.2 -> 4.4 -> 3.2` : OK > > * `3.2 -> 5.0` : Not OK > > > > #### Release support expectation > > > > We will publish clear guidelines on the Pulsar website regarding the > > expected timeline for which each release is supported and when the new > > feature and LTS releases will be available. > > > > The support model will be: > > > > * LTS > > * Released every 18 months > > * Support for 24 months > > * Security patches for 36 months > > * Feature releases > > * Released every 3 months > > * Support for 6 months > > * Security patches for 6 months > > > > This can be translated into: > > * We support the last 2 LTS releases and the last 2 feature releases > > * Security patches are provided for the past 3 LTS releases and 2 > > feature releases > > > > Users are therefore encouraged to stay in an LTS release until they are > > ready to jump into the next LTS unless they want to have access to some > of > > the features included in the latest feature releases. > > > > ### 2. Introduce a code-freeze period in the release cycle > > > > To address the problem with delayed release cycles, we are introducing a > > code freeze period that will give us time to stabilize the release code > > while not blocking new changes from being merged into master for the > > subsequent version. > > > > This code-freeze will only be adopted for LTS/feature releases, not for > any > > patch release. > > > > In a 3 months release cycle, the last 3 weeks will be marked as a code > > freeze period. The release manager will branch off from master, and he > will > > be responsible for selecting the changes that will be cherry-picked in > the > > release branch. > > > > From the code-freeze point, to minimize the risk of delaying the release, > > only bug fixes involving a regression of behavior compared to a previous > > release should be allowed. Occasional exceptions will be possible after > > higher scrutiny of the change. > > > > At the moment of the code freeze, the release manager will also prepare a > > release candidate in the same way we are doing today. Committers, > > contributors, and users will test this RC to detect issues as early as > > possible. > > > > A formal vote by the PMC will not be required at this stage (though any > > disagreement should be sent out ASAP). > > > > After 1 week, if there are any changes, the release manager will provide > a > > new RC release that the community will test again. > > > > After 1 more week, if there are any changes, a third RC will be prepared, > > and this will be submitted to vote to the PMC. Otherwise, the vote will > be > > held on an earlier RC release if no issues are found. > > > > The last 1 week will be used for the voting process and for updating > Pulsar > > website and the blog post announcing the release, which should > (hopefully) > > happen on the scheduled day. > > > > > > -- > > Matteo Merli > > <matteo.me...@gmail.com> >
