Lessons learned from advancing JDK support on trunk *should* translate into older branches making that effort much smaller; Ekaterina you have a lot of experience here so I'm curious what this raises for you. I like the productivity implications of us being able to adopt new language features faster on trunk; I think this is a solid evolution of the idea, definitely.
Distilling to bulleted lists to try and snapshot the state of the thread w/the above proposal: *[New LTS JDK Adoption]* • Trunk supports 1 JDK at a time • That JDK will be the GA LTS the day we cut a frozen branch for a new major (i.e. from moment of previous release bifurcation, trunk snapshots the JDK at that moment). Obviously there will be some flexibility here in terms of when the work lands on trunk and supporting on other branches, but the general pattern / intent hold - push to snapshot latest GA LTS JDK on trunk ASAP after branching for a major. • 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 • We up the supported language level for all supported branches to the latest supported JDK at this time • 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 • Periodically we run all CI pipelines for older JDK's per-branch (cadence TBD) • Upgrades • N-2 -> N-1: tested on JDK and JDK-1 • N-2 -> N: tested on JDK • N-1 -> N: tested on JDK That'd give us 4 upgrade paths we'd need to support and test which feels like it's in the territory of "doable on each commit" if we limit the upgrade tests to the in-jvm variety and let the periodic run capture the python upgrade tests space. On Wed, May 21, 2025, at 9:30 AM, Benedict wrote: > > Perhaps we should consider back porting support for newer Java LTS releases > to older C* versions, and suggesting users upgrade JDK first. This way we can > have trunk always on the latest LTS, advancing language feature support more > quickly. > > That is, we would have something like > > N-2: JDK, JDK-1, JDK-2 > N-1: JDK, JDK-1 > N: JDK > > I think to assist those deploying trunk and reduce churn for development, we > might only want to advance the LTS version for trunk after we release a new > major, fixing the next release’s Java version at that point. > >> • On 21 May 2025, at 13:57, Josh McKenzie <jmcken...@apache.org> wrote: >> >>> You don’t have to run every suite on every commit since as folks have >>> pointed out for the most part the JVM isn’t culprit. Need to run it enough >>> times to catch when it is for some assumption of “enough”. >> So riffing on this. We could move to something like: >> • For each given supported C* branch, confirm it **builds **on all >> supported JDKs (pre-commit verification, post-commit reactive runs) >> • Constrain language level on any given C* branch to **lowest supported >> JDK** >> • Run all reactive post-commit CI pipelines against *the *highest supported >> JDK only** >> • Once a N (day, week, month?), run all pipelines against all supported >> JDKs on all branches >> • Augment notification mechanisms so it squawks to dev list and slack on >> failure of non-highest JDK pipelines >> That approach would tweak our balance towards our perception of the >> infrequency of per-JDK failures while allowing us to "scale up" the matrix >> of tests that we perform. >> >> i.e. once a week we could have a heavy 9x run (3 branches, 3 JDK's) which we >> could then plan around and space out in terms of resource allocation, but >> otherwise we run a single set of pipelines per branch post-commit. >> >> That'd give us the confidence to say "we tested the upgrade path we're >> recommending for you" without having to pay the tax of doing it on every >> commit or allowing potential defects to pile up to a once-a-year >> JDK-specific bug-bash. >> >> In terms of JDK support when bumping (mapping of relative C* version and >> relative JDK version): >> • N-2: JDK-2, JDK-3, JDK-4 >> • N-1: JDK-1, JDK-2, JDK-3 >> • N: JDK, JDK-1, JDK-2 >> So we'd have 3 supported LTS per branch, be able to adhere to "you can >> upgrade from N-2 to N using the same JDK", and allow us to balance our CI >> coverage to our expected surfacing of defects. >> >> Then if we rev JDK we support on any given N+1, we end up with (keeping with >> N above as reference): >> • N-1: JDK-1, JDK-2, JDK-3 >> • N: JDK, JDK-1, JDK-2 >> • N+1: JDK+1, JDK, JDK-1 >> So shared JDK across all 3 on that rev is JDK-1. >> >> I think 3 LTS per branch gives us the ability to both add / drop a JDK per >> major and test / provide for upgrades from N-2 to N w/out requiring a new >> JDK cert too. >> >> On Wed, May 21, 2025, at 3:27 AM, Mick Semb Wever wrote: >>> . >>> >>>>> So yeah. I think we'll need to figure out how much coverage is reasonable >>>>> to call something "tested". I don't think it's sustainable for us to >>>>> have, at any given time, 3 branches we test across 3 JDK's each with all >>>>> our in-jvm test suites is it? >>>>> >>> >>> >>> Correct. >>> For non-upgrade tests, where testing against more than one jdk exists, we >>> should start the conversation of the value of running more than one JDK for >>> all tests per-commit CI, before we go adding a third. >>> >>> I'm not against weekly/fortnightly CI runs, just that it deserves the >>> discussion of cost (it's not necessarily cheaper due to saturation, nor are >>> we a team that has assigned build barons). The actual change is relatively >>> easy, just adding a profile and a jdk element here: >>> https://github.com/apache/cassandra/blob/trunk/.jenkins/Jenkinsfile#L126-L135 >>> >>
