Hi Josh, One observation, you wrote:
"Backports from trunk to older branches that utilize the latest language level would need to be refactored to work on older branches." This is interesting. There are two possibilities 1) As you said, in trunk, we would go with the latest language level features and if we backported and these language features are not present there because of older JDK, the patch would need to be rewritten to comply. 2) The patch would be written in such a way in trunk that it would use language features which would be present in older branches already so a backport would be easier in this regard as the code as such would not need to be reworked if it does not differ functionally a lot otherwise. It seems to me you have already identified what might happen in your older emails here: "Our risk would be patches going to trunk targeting new language features we then found out we needed to back-port would require some massaging to be compatible with older branches. I suspect that'll be a rare edge-case so seems ok?" Totally agree. I do not know what approach I would use by default but thinking about it more I would probably do 2) just for the sake of not rewriting it in older branches. A patch might be complicated already enough and keeping in mind to use newest features in trunk and not using them in older branches is just too much of a mental jugglery to handle for me. I guess that the discussion when the usage of newest language features would be recommended and justified would follow. I do not think that blindly using the latest greatest _everywhere_ is always good when maintainers need to take care of it for years in the light of backports and bug fixes etc. It probably also depends on how complex the patch is and if using the newest language level would yield some considerable performance gains etc. Regards On Tue, Jun 3, 2025 at 4:38 PM Josh McKenzie <jmcken...@apache.org> wrote: > I was attempting to convey the language level support for a given branch > at any snapshot in time; my reading of Doug's email was for something that > shouldn't be a problem with this new paradigm (since we would be doing > bugfixes targeting oldest then merge up, and new improvements and features > should be going trunk only). > > Flowing through time, here's what a new release looks like at time of > release. I'll format it as: > *C* Version / JDK Build Version / JDK Run Version(s) / Language Level* > > For our first release: > > - C* 1.0 / 11 / 11 / 11 > > Then we release the next C* version; for sake of illustration let's assume > a new JDK LTS 12: > > - C* 2.0 / 12 / 12 / 12 > - C* 1.0 / 11 / 11+12 / 11 > > Notice: we added the ability to *run* C* 1.0 on JDK12 and otherwise > didn't modify the properties of the branch re: JDK's. > > Then our 3rd release of C*, same assumption w/JDK LTS 13 support added: > > - C* 3.0 / 13 / 13 / 13 > - C* 2.0 / 12 / 12+13 / 12 > - C* 1.0 / 11 / 11+12+13 / 11 > > The ability to run on the new JDK13 is backported to all supported > branches. Otherwise: no JDK-related changes. > > And upon our 4th release, we drop support for C*1.0: > > - C* 4.0 / 14 / 14 / 14 > - C* 3.0 / 13 / 13+14 / 13 > - C* 2.0 / 12 / 12+13+14 / 12 > > The properties this gives us: > > 1. At any given time as a project we have a JDK version that shares > support between 2 branches. > 2. Any supported version of C* has a JDK that it can be run on that > allows upgrade to any other supported version of C* on that same JDK. > 3. Operators retain the ability to verify a new JDK independently of > the new C* version (i.e. bump C* 2.0 from JDK12 to JDK13, then move from C* > 2.0 on JDK13 to C* 3.0 on JDK13). > 4. We are able to aggressively adopt new language level features for > improvements and new features on trunk > 5. Bugfixes that apply to older GA branches will need to target > maximally the language level of the oldest branch to which they apply > 6. Backports from trunk to older branches that utilize the latest > language level would need to be refactored to work on older branches > > Does this exercise help clarify? > > On Tue, Jun 3, 2025, at 8:22 AM, Mick Semb Wever wrote: > > What's difficult for me to grok here is you're treating each branch as > static, while the discussion has already evolved to branches evolving over > time (with jdks being back-ported, etc). Might be more helpful to explain > states and events at different points of branch lifecycles… > > On Tue, 3 Jun 2025 at 00:16, Josh McKenzie <jmcken...@apache.org> wrote: > > > I originally had "everyone supports highest language level whee" which of > course would fail to build on older branches. > > So this new paradigm would give us the following branch:language level > support (assuming JDK bump on each release which also won't always happen): > - trunk: latest > - trunk-1: latest lang - 1 > - trunk-2: latest lang - 2 > > So while trunk-1 and trunk-2 would both *support* the newest JDK > (wherever possible) for runtime, they wouldn't be switched to the new > language level. That'd leave us able to use the newest language features on > trunk much more rapidly while *effectively snapshotting the supported > language on older branches to the lowest JDK they support* (which, when > they're last in line and about to fall off, is the JDK that was newest at > the time they came about). > > Our risk would be patches going to trunk targeting new language features > we then found out we needed to back-port would require some massaging to be > compatible with older branches. I suspect that'll be a rare edge-case so > seems ok? > > Unless I'm completely missing something. I was the one who originally just > wanted to "latest JDK All The Things" for a hot minute there. =/ > > On Mon, Jun 2, 2025, at 9:40 AM, Doug Rohrer wrote: > > Only thing I’d suggest changing here is “Trunk targets the language level > of that JDK” shouldn’t happen until after we’ve confirmed the back port of > the new JDK LTS changes to previous versions - otherwise, you have folks > starting to use new language features and then have to rip them all out > when you find that some previous supported Cassandra release can’t use that > JDK. > > Doug > > On May 27, 2025, at 10:37 AM, Josh McKenzie <jmcken...@apache.org> wrote: > > revised snapshot of the state of conversation here: > > *[New LTS JDK Adoption]* > > - Trunk supports 1 JDK at a time > - After a branch is cut for a release, we push to get trunk to support > latest LTS JDK version available at that time > - Trunk targets the language level of that JDK > - CI on trunk is that single JDK only > - We merge new JDK LTS support to all supported branches at the same > time as trunk > - In the very rare case a feature would have to be removed due to > JDK change (think UDF's scripting engine), we instead keep the maximum > allowable JDK for that feature supported on trunk and subsequent > releases. > We then drop that JDK across all branches once the oldest C* w/that > feature > ages out of support. > - Otherwise, we don't need to worry about dropping JDK support as that > will happen naturally w/the dropping of support for a branch. Branches will > slowly gain JDK support w/each subsequent trunk-based LTS integration. > > *[Branch JDK Support]* > > - N-2: JDK, JDK-1, JDK-2 > - N-1: JDK, JDK-1 > - N: JDK > > *[CI, JDK's, Upgrades]* > > - CI: > - For each branch we run per-commit CI for the latest JDK they > support > - *TODO: *Periodically we run all CI pipelines for older JDK's > per-branch (cadence TBD) > - *TODO: *We add basic perf testing across all GA branches with > reference workloads (easy-cass-stress workloads? > > <https://github.com/apache/cassandra-easy-stress/tree/main/src/main/kotlin/com/rustyrazorblade/easycassstress/workloads> > ) > - Upgrades > - N-2 -> N-1: tested on JDK and JDK-1 > - N-2 -> N: tested on JDK > - N-1 -> N: tested on JDK > > > ----------------------- > The above has 2 non-trivial CI orchestration investments: > > 1. Running all CI across all supported JDK on a cadence > 2. Adding some basic perf smoke tests > > Both seem reasonable to me. > > On Fri, May 23, 2025, at 7:39 AM, Mick Semb Wever wrote: > > > . > > > > For the rare edge case where we have to stop supporting something entirely > because it's incompatible with a JDK release (has this happened more than > the 1 time?) - I think a reasonable fallback is to just not backport new > JDK support and consider carrying forward the older JDK support until the > release w/the feature in it is EoL'ed. That'd allow us to continue to run > in-jvm upgrade dtests between the versions on the older JDK. > > > > This. > I think the idea of adding new major JDKs to release branches for a number > of reasons, in theory at least. … > > > > I *like* the idea … :) > > > > >
