Thanks for starting the discussion, Jark and Xingtong! Flink 2.0 is long overdue. In the past, the expectations for such a release were unreasonably high. I think everybody had a different understanding of what exactly the criteria were. This led to releasing 18 minor releases for the current major version.
What I'm most excited about for Flink 2.0 is removal of baggage that Flink has accumulated over the years: - Removal of Scala, deprecated interfaces, unmaintained libraries and APIs (DataSet) - Consolidation of configuration - Merging of multiple scheduler implementations - Ability to freely combine batch / streaming tasks in the runtime When I look at https://docs.google.com/document/d/1_PMGl5RuDQGlV99_gL3y7OiRsF0DgCk91Coua6hFXhE/edit , I'm a bit skeptical we will even be able to reach all these goals. I think we have to prioritize and try to establish a deadline. Otherwise we will end up never releasing 2.0. +1 on Flink 2.0 by May 2024 (not a hard deadline but I think having a deadline helps). -Max On Wed, Apr 26, 2023 at 10:08 AM Chesnay Schepler <ches...@apache.org> wrote: > > > /Instead of defining compatibility guarantees as "this API won't > change in all 1.x/2.x series", what if we define it as "this API won't > change in the next 2/3 years"./ > > I can see some benefits to this approach (all APIs having a fixed > minimum lifetime) but it's just gonna be difficult to communicate. > Technically this implies that every minor release may contain breaking > changes, which is exactly what users don't want. > > What problems to do you see in creating major releases every N years? > > > /IIUC, the milestone releases are a breakdown of the 2.0 release, > while we are free to introduce breaking changes between them. And you > suggest using longer-living feature branches to keep the master branch > in a releasable state (in terms of milestone releases). Am I > understanding it correctly?/ > > I think you got the general idea. There are a lot of details to be > ironed out though (e.g., do we release connectors for each milestone?...). > > Conflicts in the long-lived branches are certainly a concern, but I > think those will be inevitable. Right now I'm not _too_ worried about > them, at least based on my personal wish-list. > Maybe the milestones could even help with that, as we could preemptively > decide on an order for certain changes that have a high chance of > conflicting with each other? > I guess we could do that anyway. > Maybe we should explicitly evaluate how invasive a change is (in > relation to other breaking changes!) and manage things accordingly > > > Other thoughts: > > We need to figure out what this release means for connectors > compatibility-wise. The current rules for which versions a connector > must support don't cover major releases at all. > (This depends a bit on the scope of 2.0; if we add binary compatibility > to Public APIs and promote a few Evolving ones then compatibility across > minor releases becomes trivial) > > What process are you thinking of for deciding what breaking changes to > make? The obvious choice would be FLIPs, but I'm worried that this will > overload the mailing list / wiki for lots of tiny changes. > > Provided that we agree on doing 2.0, when would we cut the 2.0 branch? > Would we wait a few months for people to prepare/agree on changes so we > reduce the time we need to merge things into 2 branches? > > On 26/04/2023 05:51, Xintong Song wrote: > > Thanks all for the positive feedback. > > > > @Martijn > > > > If we want to have that roadmap, should we consolidate this into a > >> dedicated Confluence page over storing it in a Google doc? > >> > > Having a dedicated wiki page is definitely a good way for the roadmap > > discussion. I haven't created one yet because it's still a proposal to have > > such roadmap discussion. If the community agrees with our proposal, the > > release manager team can decide how they want to drive and track the > > roadmap discussion. > > > > @Chesnay > > > > We should discuss how regularly we will ship major releases from now on. > >> Let's avoid again making breaking changes because we "gotta do it now > >> because 3.0 isn't happening anytime soon". (e.g., every 2 years or > >> something) > > > > I'm not entirely sure about shipping major releases regularly. But I do > > agree that we may want to avoid the situation that "breaking changes can > > only happen now, or no idea when". Instead of defining compatibility > > guarantees as "this API won't change in all 1.x/2.x series", what if we > > define it as "this API won't change in the next 2/3 years". That should > > allow us to incrementally iterate the APIs. > > > > E.g., in 2.a, all APIs annotated as `@Stable` will be guaranteed compatible > > until 2 years after 2.a is shipped, and in 2.b if the API is still > > annotated `@Stable` it extends the compatibility guarantee to 2 years after > > 2.b is shipped. To remove an API, we would need to mark it as `@Deprecated` > > and wait for 2 years after the last release in which it was marked > > `@Stable`. > > > > My thinking goes rather in the area of defining Milestone releases, each > >> Milestone targeting specific changes. > >> > > I'm trying to understand what you are suggesting here. IIUC, the milestone > > releases are a breakdown of the 2.0 release, while we are free to introduce > > breaking changes between them. And you suggest using longer-living feature > > branches to keep the master branch in a releasable state (in terms of > > milestone releases). Am I understanding it correctly? > > > > I haven't thought this through. My gut feeling is this might be a good > > direction to go, in terms of keeping things organized. The risk is the cost > > of merging feature branches and rebasing feature branches after other > > features are merged. That depends on how close the features are related to > > each other. E.g., reorganization of the project modules and dependencies > > may change the project structure a lot, which may significantly affect most > > of the feature branches. Maybe we can identify such widely-affecting > > changes and perform them at the beginning or end of the release cycle. > > > > Best, > > > > Xintong > > > > > > > > On Wed, Apr 26, 2023 at 8:23 AM ConradJam<jam.gz...@gmail.com> wrote: > > > >> Thanks Xintong and Jark for kicking off the great discussion! > >> > >> I checked the list carefully. The plans are detailed and most of the > >> problems are covered > >> Some of the ideas Chesnay mentioned, I think we should iterate in > >> small steps and collect feedback in time > >> Looking forward to the start of the work of Flink2.0, I am willing to > >> provide assistance ~ > >> > >> Xintong Song<tonysong...@gmail.com> 于2023年4月25日周二 19:10写道： > >>> Hi everyone, > >>> > >>> I'd like to start a discussion on planning for a Flink 2.0 release. > >>> > >>> AFAIK, in the past years this topic has been mentioned from time to time, > >>> in mailing lists, jira tickets and offline discussions. However, few > >>> concrete steps have been taken, due to the significant determination and > >>> efforts it requires and distractions from other prioritized focuses. > >> After > >>> a series of offline discussions in the recent weeks, with folks mostly > >> from > >>> our team internally as well as a few from outside Alibaba / Ververica > >>> (thanks for insights from Becket and Robert), we believe it's time to > >> kick > >>> this off in the community. > >>> > >>> Below are some of our thoughts about the 2.0 release. Looking forward to > >>> your opinions and feedback. > >>> > >>> > >>> ## Why plan for release 2.0? > >>> > >>> > >>> Flink 1.0.0 was released in March 2016. In the past 7 years, many new > >>> features have been added and the project has become different from what > >> it > >>> used to be. So what is Flink now? What will it become in the next 3-5 > >>> years? What do we think of Flink's position in the industry? We believe > >>> it's time to rethink these questions, and draw a roadmap towards another > >>> milestone, a milestone that worths a new major release. > >>> > >>> > >>> In addition, we are still providing backwards compatibility (maybe not > >>> perfectly but largely) with APIs that we designed and claimed stable 7 > >>> years ago. While such backwards compatibility helps users to stick with > >> the > >>> latest Flink releases more easily, it sometimes, and more and more over > >>> time, also becomes a burden for maintenance and a limitation for new > >>> features and improvements. It's probably time to have a comprehensive > >>> review and clean-up over all the public APIs. > >>> > >>> > >>> Furthermore, next year is the 10th year for Flink as an Apache project. > >>> Flink joined the Apache incubator in April 2014, and became a top-level > >>> project in December 2014. That makes 2024 a perfect time for bringing out > >>> the release 2.0 milestone. And for such a major release, we'd expect it > >>> takes one year or even longer to prepare for, which means we probably > >>> should start now. > >>> > >>> > >>> ## What should we focus on in release 2.0? > >>> > >>> > >>> - Roadmap discussion - How do we define and position Flink for now and > >>> in future? This is probably something we lacked. I believe some > >> people have > >>> thought about it, but at least it's not explicitly discussed and > >> aligned in > >>> the community. Ideally, the 2.0 release should be a result of the > >> roadmap. > >>> - Breaking changes - Important improvements, bugfixes, technical debts > >>> that involve breaking of API backwards compatibility, which can only > >> be > >>> carried out in major releases. > >>> - With breaking API changes, we may need multiple 2.0-alpha/beta > >>> versions to collect feedback. > >>> - Key features - Significant features and improvements (e.g., new user > >>> stories, architectural upgrades) that may change how users use Flink > >> and > >>> its position in the industry. Some items from this category may also > >>> involve API breaking changes or significant behavior changes. > >>> - There are also opinions that we should stay focused as much as > >>> possible on the breaking changes only. Incremental / non-breaking > >>> improvements and features, or anything that can be added in 2.x > >> minor > >>> releases, should not block the 2.0 release. > >>> > >>> It might be better to discuss the detailed technical items later in > >> another > >>> thread, to keep the current discussion focused on the overall proposal, > >> and > >>> to leave time for all parties to think about their technical plans. For > >>> your reference, I've attached a preliminary list of work items proposed > >> by > >>> Alibaba / Ververica [1]. Note that the listed items are still being > >>> carefully evaluated and prioritized, and may change in future. > >>> > >>> > >>> ## How do we manage the release? > >>> > >>> > >>> #### Release Process > >>> > >>> > >>> We'd expect the release process for Flink 2.0 to be different from the > >> 1.x > >>> releases. > >>> > >>> > >>> A major difference is that, we think the timeline-based release > >> management > >>> may not be suitable. The idea behind the timeline-based approach is that > >> we > >>> can have more frequent releases and deliver completed features to users > >>> earlier, while incompleted features can be postponed to the next release > >>> which won't be too late with the short release cycle. However, for > >> breaking > >>> changes that can only take place in major releases, the price for > >> missing a > >>> release is too high. > >>> > >>> > >>> Alternatively, we probably should discuss and agree on a list of > >> must-have > >>> work items. That doesn't mean keep postponing the release upon a few > >>> delayed features. In fact, we would need to closely monitor the progress > >> of > >>> the must-have items during the entire release cycle, making sure they are > >>> taken care of by contributors with enough expertise and capacities. > >>> > >>> > >>> #### Timeline > >>> > >>> > >>> The release cycle should be decided according to the feature list, > >>> especially the must-have items that we plan to do in the release. > >> However, > >>> a target feature freeze date would still be helpful when making the plan, > >>> so that we don't pack too many things into the release. We propose to aim > >>> for a feature freeze around mid 2024, so that in case must-have items are > >>> delayed, we still have a good chance to make the release happen by the > >> end > >>> of 2024. > >>> > >>> > >>> #### Branch > >>> > >>> > >>> A longer release cycle also means we probably should keep shiping the 1.x > >>> releases while preparing for the 2.0 release. We may cut a release-1 from > >>> master, on which we can keep developing and release 1.x releases. The > >>> version on the master branch will then become '2.0-SNAPSHOT'. > >>> > >>> > >>> #### Release Manager > >>> > >>> > >>> Given the new and to-be-explored release process, longer cycle and higher > >>> synchronization requirements, we'd expect the 2.0 release to be more > >>> challenging than previous 1.x releases. Therefore, we'd like to propose > >> to > >>> assemble a release management team with 4-5 experienced PMC members. Jark > >>> and I would like to volunteer as 2 of the release managers. > >>> > >>> > >>> Looking forward to your thoughts. > >>> > >>> > >>> Best, > >>> > >>> Jark & Xintong > >>> > >>> > >>> [1] > >>> > >> https://docs.google.com/document/d/1_PMGl5RuDQGlV99_gL3y7OiRsF0DgCk91Coua6hFXhE/edit?usp=sharing > >> > >> -- > >> Best > >> > >> ConradJam > >>
