More details about the JDK bug here https://bugs.openjdk.org/browse/JDK-8277529
Related Jira ticket https://issues.apache.org/jira/browse/FLINK-24998 ________________________________ From: Jing Ge via user <user@flink.apache.org> Sent: Monday, April 24, 2023 11:15 PM To: Chesnay Schepler <ches...@apache.org> Cc: Piotr Nowojski <pnowoj...@apache.org>; Alexis Sarda-Espinosa <sarda.espin...@gmail.com>; Martijn Visser <martijnvis...@apache.org>; d...@flink.apache.org <d...@flink.apache.org>; user <user@flink.apache.org> Subject: Re: [Discussion] - Release major Flink version to support JDK 17 (LTS) EXTERNAL EMAIL Thanks Chesnay for working on this. Would you like to share more info about the JDK bug? Best regards, Jing On Mon, Apr 24, 2023 at 11:39 AM Chesnay Schepler <ches...@apache.org<mailto:ches...@apache.org>> wrote: As it turns out Kryo isn't a blocker; we ran into a JDK bug. On 31/03/2023 08:57, Chesnay Schepler wrote: https://github.com/EsotericSoftware/kryo/wiki/Migration-to-v5#migration-guide Kroy themselves state that v5 likely can't read v2 data. However, both versions can be on the classpath without classpath as v5 offers a versioned artifact that includes the version in the package. It probably wouldn't be difficult to migrate a savepoint to Kryo v5, purely from a read/write perspective. The bigger question is how we expose this new Kryo version in the API. If we stick to the versioned jar we need to either duplicate all current Kryo-related APIs or find a better way to integrate other serialization stacks. On 30/03/2023 17:50, Piotr Nowojski wrote: Hey, > 1. The Flink community agrees that we upgrade Kryo to a later version, which > means breaking all checkpoint/savepoint compatibility and releasing a Flink > 2.0 with Java 17 support added and Java 8 and Flink Scala API support > dropped. This is probably the quickest way, but would still mean that we > expose Kryo in the Flink APIs, which is the main reason why we haven't been > able to upgrade Kryo at all. This sounds pretty bad to me. Has anyone looked into what it would take to provide a smooth migration from Kryo2 -> Kryo5? Best, Piotrek czw., 30 mar 2023 o 16:54 Alexis Sarda-Espinosa <sarda.espin...@gmail.com<mailto:sarda.espin...@gmail.com>> napisał(a): Hi Martijn, just to be sure, if all state-related classes use a POJO serializer, Kryo will never come into play, right? Given FLINK-16686 [1], I wonder how many users actually have jobs with Kryo and RocksDB, but even if there aren't many, that still leaves those who don't use RocksDB for checkpoints/savepoints. If Kryo were to stay in the Flink APIs in v1.X, is it impossible to let users choose between v2/v5 jars by separating them like log4j2 jars? [1] https://issues.apache.org/jira/browse/FLINK-16686 Regards, Alexis. Am Do., 30. März 2023 um 14:26 Uhr schrieb Martijn Visser <martijnvis...@apache.org<mailto:martijnvis...@apache.org>>: Hi all, I also saw a thread on this topic from Clayton Wohl [1] on this topic, which I'm including in this discussion thread to avoid that it gets lost. From my perspective, there's two main ways to get to Java 17: 1. The Flink community agrees that we upgrade Kryo to a later version, which means breaking all checkpoint/savepoint compatibility and releasing a Flink 2.0 with Java 17 support added and Java 8 and Flink Scala API support dropped. This is probably the quickest way, but would still mean that we expose Kryo in the Flink APIs, which is the main reason why we haven't been able to upgrade Kryo at all. 2. There's a contributor who makes a contribution that bumps Kryo, but either a) automagically reads in all old checkpoints/savepoints in using Kryo v2 and writes them to new snapshots using Kryo v5 (like is mentioned in the Kryo migration guide [2][3] or b) provides an offline tool that allows users that are interested in migrating their snapshots manually before starting from a newer version. That potentially could prevent the need to introduce a new Flink major version. In both scenarios, ideally the contributor would also help with avoiding the exposure of Kryo so that we will be in a better shape in the future. It would be good to get the opinion of the community for either of these two options, or potentially for another one that I haven't mentioned. If it appears that there's an overall agreement on the direction, I would propose that a FLIP gets created which describes the entire process. Looking forward to the thoughts of others, including the Users (therefore including the User ML). Best regards, Martijn [1] https://lists.apache.org/thread/qcw8wy9dv8szxx9bh49nz7jnth22p1v2 [2] https://lists.apache.org/thread/gv49jfkhmbshxdvzzozh017ntkst3sgq [3] https://github.com/EsotericSoftware/kryo/wiki/Migration-to-v5 On Sun, Mar 19, 2023 at 8:16 AM Tamir Sagi <tamir.s...@niceactimize.com<mailto:tamir.s...@niceactimize.com>> wrote: I agree, there are several options to mitigate the migration from v2 to v5. yet, Oracle roadmap is to end JDK 11 support in September this year. ________________________________ From: ConradJam <jam.gz...@gmail.com<mailto:jam.gz...@gmail.com>> Sent: Thursday, March 16, 2023 4:36 AM To: d...@flink.apache.org<mailto:d...@flink.apache.org> <d...@flink.apache.org<mailto:d...@flink.apache.org>> Subject: Re: [Discussion] - Release major Flink version to support JDK 17 (LTS) EXTERNAL EMAIL Thanks for your start this discuss I have been tracking this problem for a long time, until I saw a conversation in ISSUSE a few days ago and learned that the Kryo version problem will affect the JDK17 compilation of snapshots [1] FLINK-24998 , As @cherry said it ruined our whole effort towards JDK17 I am in favor of providing an external tool to migrate from Kryo old version checkpoint to the new Kryo new checkpoint at one time (Maybe this tool start in flink 2.0 ?), does this tool currently have any plans or ideas worth discuss I think it should not be difficult to be compatible with JDK11 and JDK17. We should indeed abandon JDK8 in 2.0.0. It is also mentioned in the doc that it is marked as Deprecated [2] Here I add that we need to pay attention to the version of Scala and the version of JDK17 [1] FLINK-24998 IGSEGV in Kryo / C2 CompilerThread on Java 17 https://issues.apache.org/jira/browse/FLINK-24998 [2] FLINK-30501 Update Flink build instruction to deprecate Java 8 instead of requiring Java 11 https://issues.apache.org/jira/browse/FLINK-30501 Tamir Sagi <tamir.s...@niceactimize.com<mailto:tamir.s...@niceactimize.com>> 于2023年3月16日周四 00:54写道： > Hey dev community, > > I'm writing this email to kick off a discussion following this epic: > FLINK-15736<https://issues.apache.org/jira/browse/FLINK-15736>. > > We are moving towards JDK 17 (LTS) , the only blocker now is Flink which > currently remains on JDK 11 (LTS). Flink does not support JDK 17 yet, with > no timeline, the reason, based on the aforementioned ticket is the > following tickets > > 1. FLINK-24998 - SIGSEGV in Kryo / C2 CompilerThread on Java 17< > https://issues.apache.org/jira/browse/FLINK-24998>. > 2. FLINK-3154 - Update Kryo version from 2.24.0 to latest Kryo LTS > version<https://issues.apache.org/jira/browse/FLINK-3154> > > My question is whether it is possible to release a major version (Flink > 2.0.0) using the latest Kryo version for those who don't need to restore > old savepoints/checkpoints in newer format. > > 1. Leverage JDK 17 features within JVM > 2. Moving from the old format to the newer one will be handled only > once - a mitigation can be achieved by a conversion tool or external > serializers, both can be provided later on. > > I'd like to emphasize that the next JDK LTS (21) will be released this > September. furthermore, Flink already supports JDK 12-15, which is very > close to JDK 17 (LTS) - that was released in September 2021. JDK 11 will > become a legacy soon, as more frameworks moving towards JDK 17 and are less > likely to support JDK 11 in the near future. (For example, Spring Boot 3 > requires JDK 17 already). > > Thank you for your consideration of my request. > > Tamir. > > > > > Confidentiality: This communication and any attachments are intended for > the above-named persons only and may be confidential and/or legally > privileged. Any opinions expressed in this communication are not > necessarily those of NICE Actimize. If this communication has come to you > in error you must take no action based on it, nor must you copy or show it > to anyone; please delete/destroy and inform the sender by e-mail > immediately. > Monitoring: NICE Actimize may monitor incoming and outgoing e-mails. > Viruses: Although we have taken steps toward ensuring that this e-mail and > attachments are free from any virus, we advise that in keeping with good > computing practice the recipient should ensure they are actually virus free. > -- Best ConradJam Confidentiality: This communication and any attachments are intended for the above-named persons only and may be confidential and/or legally privileged. Any opinions expressed in this communication are not necessarily those of NICE Actimize. If this communication has come to you in error you must take no action based on it, nor must you copy or show it to anyone; please delete/destroy and inform the sender by e-mail immediately. Monitoring: NICE Actimize may monitor incoming and outgoing e-mails. Viruses: Although we have taken steps toward ensuring that this e-mail and attachments are free from any virus, we advise that in keeping with good computing practice the recipient should ensure they are actually virus free. Confidentiality: This communication and any attachments are intended for the above-named persons only and may be confidential and/or legally privileged. Any opinions expressed in this communication are not necessarily those of NICE Actimize. If this communication has come to you in error you must take no action based on it, nor must you copy or show it to anyone; please delete/destroy and inform the sender by e-mail immediately. Monitoring: NICE Actimize may monitor incoming and outgoing e-mails. Viruses: Although we have taken steps toward ensuring that this e-mail and attachments are free from any virus, we advise that in keeping with good computing practice the recipient should ensure they are actually virus free.
