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
